research on gut health and depression

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• v.12(8); 2020 Aug

Gut Microbiome and Depression: How Microbes Affect the Way We Think

Therese limbana.

1 Psychiatry, California Institute of Behavioral Neurosciences and Psychology, Fairfield, USA

Noha Eskander

The gut microbiome serves an important role in the human body. Reportedly, one of the benefits of these microflora is on mental health. Once established, food and other dietary sources that enhance quality microbiome content in our gastrointestinal system will be a significant consideration in individuals’ day to day lives. This literature review conducted a PubMed search for studies about the gut microbiome and its relation to depression. In using several Medical Subject Heading (MeSH) keywords, relevant literature was selected. A total of 26 articles were selected after applying the inclusion and exclusion criteria, and after checking the articles’ accessibility. This literature would like to establish the role of the gut microbiome in depression. This study's findings showed that there is a strong association of microbiome function to mental well-being.

Introduction and background

Microbes in the gut are of great importance to the human body. The composition of one's gut microbiota is individually specific and is highly influenced by genetics, growth and development, and location [ 1 ]. With an estimated 1018 microorganisms, mostly made up of anaerobic bacteria, the gut microbiome is responsible for multiple functions in bowel movement, digestion of food, and absorption of nutrients [ 2 ]. With the brain and the gut working in a bi-directional manner, they could affect each other's functions and significantly impact stress, anxiety, depression, and cognition [ 3 ].

Depression is a serious mental illness caused by multiple factors [ 4 ]. It is described as low emotional disposition, loss of confidence, and apathy [ 2 ]. Depression is suggested to result from complex interactions of an individual's genetics and their environment. Major depressive disorder (MDD) tops the spot in contributing to the worldwide disease burden, as claimed by the World Health Organization (WHO) [ 5 ]. Based on the WHO reports, there are approximately 350 million people affected by depression [ 6 ]. Research findings showed that healthy gut microflora transmits brain signals through the pathways involved in neurogenesis, neural transmission, microglial activation, and behavioral control under stable or stressful conditions. This process led several studies to recognize the importance of microbiomes in managing mental health issues [ 7 ]. In depression, there is also dysregulation of the neuroendocrine and neuroimmune pathways [ 8 , 9 ]. More than 20% of Inflammatory Bowel Disease (IBD) patients have sleep disturbances and depressed behaviors. By acknowledging that inflammation affects the brain and how one thinks, treatments addressing this phenomenon have grown its popularity in IBD patients and healthy populations [ 10 ].

The study of gut microbiota affecting mental health is a relatively new research topic that has gained popularity these past years. There are still parts that need to be delved deeper and to be understood. A comprehensive evaluation of the gut microbiome leading to depression reveals flaws in the research design and how it was performed, suggesting that results may be subpar compared to other research studies [ 11 ]. Furthermore, more studies are needed to ascertain the benefits of using probiotic interventions in promoting stable brain processing [ 3 ]. For example, the laboratory findings in rodent studies have not yet been clear on the effects of these gut microbiota in modulating psychiatric illnesses [ 12 ]. The degree of changes in function and composition of gastrointestinal microflora leading to depression [ 9 ] and the causal connection of both the bacterial commensals and depression have to be fully understood to establish the role of the gut microbiome in depression [ 13 ]. The environmental factors contributing to MDD are also still unclear [ 5 ]. With all the findings noted in the research of gut microbiome and depression, this literature review aims to establish an association between gut microbiota and depression and how these gut microbes affect mental health.

A literature search was done through the use of MeSH keywords in PubMed. Table ​ Table1 1 indicates the keywords used in a literature search. 

The study's inclusion criteria include the use of human studies, published papers in the English language, and all the abstracts and full papers. On the other hand, the exclusion criteria were fully non-human studies and non-English language.

Table ​ Table2 2 presents the total number of articles based on the inclusion and exclusion criteria.

MeSH: Medical Subject Heading

After doing a refined search using the MeSH keywords 'Gastrointestinal Microbiome (Subheading- Etiology, and Physiology)' and 'Depression (Subheading- Anatomy and Histology, Etiology, and Psychology),' 27 articles were retrieved. Out of the 27 articles, one was excluded because of the unavailability of abstract and inability to access the paid article. 

Figure ​ Figure1 1 below exhibits the process of the current literature review.

Overview  

There are approximately 100 trillion microbes from a thousand diverse species residing in the human gut. Each microflora serves a specific role and is affected by food choices, genes, medication exposures, and stressful events [ 1 ]. Gut microbiome or intestinal microflora serves several purposes in the body. They affect the promotion of gastrointestinal digestion, food absorption, and maintenance of intestinal integrity. In the past few years, the relationship of gut dysbiosis to disease conditions are established. There is a bidirectional relationship between the two entities, and studies noticed a specific microbe for every disease developed, especially the illnesses in mental health [ 2 ]. There are several pathways implicated in the link. Several of the pathways are neuroimmune, neuroendocrine, and sensory-neural. Although a connection is noted between microflora leading to depression, there is still a need to establish the causality link by analyzing the role of each gut microbiota- the chronology of events that comes first is yet being studied. In the case of rodents, depression developed in fecal transplant recipients after receiving fecal samples from MDD patients. However, rodents who have experienced stress and depression showed a reduction in gut microbiome content and diversity [ 13 ].

Gut Microbiome and Depression

Any permutations in the gut microbiome composition trigger microbial lipopolysaccharides (LPS) production. It, in turn, activates inflammatory responses. Cytokines send signals to the vagus nerve, which links the process to the hypothalamic-pituitary-adrenal axis that consequently causes behavioral effects. Another school of thought suggests that the gastrointestinal (GI) tract's inflammation leads to neuroinflammation. It then fuels microglial action and triggers the kynurenine pathway. All these processes induce depression [ 14 ]. In human studies, evidence of changes in microflora composition explains depression [ 8 ]. The bidirectional connection between gut microflora and depression has been well reinforced by research. But as mentioned, the direction of causality between the two entities still needs to be determined [ 13 ]. Many research studies have directed their attention to understanding the interaction between the gut microbiome and the brain. The use of supplemental probiotics has shown promising effects on addressing brain-associated problems. Although encouraging, more research is needed to ascertain probiotics' mode of action and side-effects [ 3 ]. Under stable and stressful conditions, the gut commensals may send signals to the central nervous system (CNS) through different pathways such as neurogenesis, neurotransmission, and many more. The potential of stressful events to control our gut microbiome content and the ability of these bacterial commensals to manage stress levels have been uncovered.

Patients diagnosed with mental conditions, including depression, have demonstrated gut microbiome dysbiosis [ 7 ]. Intricate relationships of the individual gene and the surroundings are pointed out to contribute to the development of MDD. The lack of bacterial microflora in germ-free (GF) mice reduced the immobile period in the forced swimming test compared to the healthy mice. The composition and diversity of bacteria between healthy and depressed patients showed significant disparity with the depressed group showing mostly Firmicutes, Bacteroides, and Actinobacteria in the gut. This supports how the gut bacterial content's dysbiosis changes the behavior of the host [ 5 ]. In recent years, neurobiological modifications have been related to the development of depression. Inflammation is one of the connections that leads to the modification process. It showed high levels of concentration of neurotransmitters in inflammation, and increasing psychological processes are noted. In maintaining the regulation of physiology, the host must keep a stable microbial community safely to say that these microbiomes have control in curbing depression [ 6 ]. Several factors also send signals to the brain regarding the gut state, such as infectious substances, cytokines, antibiotics, and vagal sensory fibers, to name a few. The hypothalamic-pituitary-adrenal axis also metabolizes microbiome diversity and nutrient ability [ 15 ].

Inflammation to Depression

Studies have shown that patients with inflammatory diseases are prone to depression. Worsening IBD conditions are anticipated by more frequent bouts of depressed symptoms. The theory is that dysregulation of the pathways involved in the gut-brain axis is linked to this phenomenon [ 10 ]. In understanding the interplay of inflammation leading to depression, and depression worsening cytokine responses, it is essential to fully understand the process to stop this vicious cycle [ 16 ]. New research findings reveal that prolonged neuroinflammation affects brain functions, which could dictate the individual's mood and behavior [ 4 ]. The interaction of both depression and inflammation is like a vicious cycle fueling each other. Inflammation is one of the leading forces in the development of depression. It consequently triggers more cytokine production in response to the stressors that are not innate to the human body. There is an amplified inflammatory process when several factors, including genetic risks, pathogens, and environmental stressors, co-occur. The effects noted like depression and other harmful practices such as poor diet choices and lack of exercise may hasten the inflammatory reaction uncontrollably and worsen depression. Any stressful events experienced by an individual dictates the diversity and composition of their gut commensals. The recurrent, immense, and chronic inflammation worsens mental and physical conditions. When both inflammation and depression are presented in a patient, it is essential to provide management for both issues to resolve the problem [ 17 ].

The prevalence of depression in IBD patients has been increasing, which worsens the affected groups’ quality of life. Both conditions involve immune-inflammatory, oxidative (IO), and nitrosative stress (NS) pathways. These are exhibited by increasing levels of pro-inflammatory cytokines and acute-phase reactants as well as decreasing levels of negative acute phase reactant and many more. The IO and NS processes of both depression and IBD overlap, insinuating a causal relationship. These processes have vital importance in the management of either condition [ 17 ].

Certain types of diet are associated with improving mental health. One example is the Mediterranean diet, which promotes healthy eating, unlike the Western counterparts. Diet choices significantly affect other body systems, such as the endocrine, immune and gastrointestinal systems [ 18 ]. One study found that Western diets contribute to the dysbiotic conditions that send brain signals to alter diet intake behavior [ 19 ]. High-fat consumption not only leads to obesity but also causes widespread inflammation of body systems. The gut microbiome may alter the harmful effects of the high-fat diet, improving mood and behavior. By modulating gut microbiome composition through proper nutrition and probiotics, we also help decrease anxiety and depression [ 4 ]. Lactobacilli and inflammation are also recognized to affect the brain pathway and when an imbalance occurs, mood disorders develop [ 20 ].

We are still in the early period of research into how diet can influence our brain processes. A large-scale clinical trial conducted did not show significant effects of the Mediterranean diet on the behavior of adults with subclinical manifestations of depression. However, when looking at the smaller-scale clinical trials, improvement of depressed symptoms was noted after shifting the current diet to the Mediterranean. These trials also considered the subjects' expectations and how dietary changes have improved their overall perception of their well-being [ 18 ]. Although studies regarding this phenomenon are conducted to depressed human populations and rodent models, the evidence proving that gut microflora dysbiosis is the main causative factor is still inadequate. Clinical parameters to measure gut microbiome alteration are yet to be established [ 19 ].

Marital Potential to Develop Diseases

Stressful times push individuals to engage in unhealthy behaviors, such as lack of sleep and unhealthy food choices. These practices lead to increasing gut leakiness that promotes inflammation and immunosenescence. These risks are modified through reverting to healthy lifestyle practices by proper diet, exercise, and adequate sleep [ 21 ]. In married couples, it was found that they do not just affect each partner’s physical health but also mental health. The different life stressors, challenges, and disturbance in their shared lifestyles influence their health condition. They are promoting some disease risks, which may also affect their gut microbiota homeostasis. Exposure to chronic relationship problems increased the chance to develop metabolic syndrome and cardiovascular issues through their bodies' production of insulin and peaked triglyceride levels after poor quality dietary intake [ 21 ].

Several studies strongly support the association of gut microbiome in the development of depression. Table ​ Table3 3 shows some of the studies that link the gut commensals and their effect on the hosts' mental health.

CRP- C- Reactive Protein; ARNTL- Aryl hydrocarbon Receptor Nuclear Translocator-Like; CPG- 5'-C-phosphate-G-3'; LBP- Lipopolysaccharide-Binding Protein; CD14- Cluster of Differentiation 14; MDD- Major Depressive Disorder

Although numerous studies have been conducted about the gut microbiome and its strong effect on mental health, there are still studies that negate these findings and suggest conducting more research experiments and better methods in finding out more details. Table ​ Table4 4 contains some of the reviews not supportive of the connection between the gut microbiome and depression. 

BMI- Body Mass Index; rRNA- Ribosomal Ribonucleic Acid

This literature review also found the importance of an individual's resilience in maintaining one's immunity. The immune system serves as one of the main body systems affected by the gut microbiome to the depression pathway. Resilience is the ability to endure and recover from adverse events encountered by the individual. Research findings showed that the qualities that assist in fostering resilience have protective effects in combatting the stressors affecting other systems of the body. More data were retrieved, indicating that the resilient group of people has a unique immunophenotype compared to their stress-vulnerable counterparts. However, it was found that this stress-vulnerable group can be converted to resilient individuals or vice-versa by manipulating their immunophenotype. The resilient inflammatory phenotype also tenders an ability to bounce back better from inflammatory symptoms [ 25 ]. Although the link of gut microbiota to mental health is growing in popularity to the research world, more studies are needed to prove the relationship between resilience and immunity [ 25 ].

After gaining knowledge about how microbiomes affect human behavior, giving importance to the food we eat, refraining from taking those medications with an adverse impact on our gut commensals, and considering probiotic supplements part of our diet regimen is essential [ 14 ]. The relevance of gut microbiota to the body remains unpopular to society, albeit already relevant to the research community. In the quest for reducing IBD exacerbations, depressive behaviors are also targeted by providing anti-inflammatory management [ 10 ]. It will be a medical breakthrough once the inflammatory pathway is proven to be a part of the pathophysiology of psychiatric diseases. More clinicians will be aware that stressful events encountered or the genes inherited are not the only contributors to the mental condition, but also the inflammatory process experienced by the patient. Effective psychiatric illness management would mean that we address both the behavioral aspect of illness and the inflammatory process experienced by the patient, leading to overall health [ 16 ]. Gut and neural pathways are other aspects implicated in the development of depression after exposure to traumatic events in early life, early drug intake destroying the gut commensals, and poor childhood nutrition choices. This information is an essential guide for taking care of the pediatric population [ 6 ]. 

A good understanding of the bacterial commensals’ mechanism may lead to microbiome-based breakthrough treatments [ 7 ]. It is recommended that more laboratory investigations be performed to establish the microbiota-gut-brain (MGB) axis functions [ 26 ]. Although the MGB axis is slowly gaining in popularity, there are still limited research studies on the topic. Complete understanding of the link of the MGB axis and neuroimmune systems directs the future to more successful depression management [ 15 ]. More laboratory studies are highly encouraged to be conducted focusing on ascertaining the details on specific concentration levels of gut microbiota in the development of specific mental health illnesses. Also, more large-scale studies are needed to strengthen the results of earlier research studies. The present literature review has limitations that should be taken into consideration. The study restricts its scope in terms of language (English language studies only), and only human studies were covered. All types of research designs were welcomed in this literature review.

Conclusions

This study intends to determine the role of the gut microbiome in mental health and depression. This literature review established a strong link of microbes in the gastrointestinal tract, affecting how individuals think and how the gut-brain axis serves as an essential pathway in considering the management of several mental issues and psychiatric illnesses. Although promising, gut microbiome studies have a long way to go. More laboratory experiments need to be proven regarding the composition, qualities, or concentrations of gut microorganisms dictating certain behaviors within the spectrum of mental health and illness. We are still far from establishing the role of these fantastic gut microbes to how we think. Nevertheless, once we understand the specifics fully, we will be able to break the hindrances in the management of many intractable psychiatric diseases.

The content published in Cureus is the result of clinical experience and/or research by independent individuals or organizations. Cureus is not responsible for the scientific accuracy or reliability of data or conclusions published herein. All content published within Cureus is intended only for educational, research and reference purposes. Additionally, articles published within Cureus should not be deemed a suitable substitute for the advice of a qualified health care professional. Do not disregard or avoid professional medical advice due to content published within Cureus.

The authors have declared that no competing interests exist.

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What’s the Gut Microbiome Got to Do With Depression?

Pikovit44/Getty

Key Takeaways

• A recent study linked specific gut microbes to higher rates of depression.
• The study adds to the evidence of an important connection between the gut and brain—also called the “gut-brain axis.”
• Experts say that understanding the gut-brain connection can help us build systems, communities, and lifestyles that take a more integrated approach to health.

The digestive system’s main job might be to break down food and keep us nourished, but that’s not all the gut is good for. One exciting area of research is examining how the gut is connected to the brain.

We’re learning that the link between these systems is more than feeling “butterflies in our stomach” when we’re nervous or “losing our appetite” when we’re upset. Recently, researchers in Finland found a link between specific gut microbes and depression .

The authors of this recent study wrote that their findings add to the “increasing evidence” that gut microbes are “likely to influence host behavior.”

One way that they do this is through the “systemic modulation of hormones and metabolites along the gut-brain axis”—in other words, a path between the mind and the body.

Understanding the Gut-Brain Axis

Since it’s a relatively new field, there are some big questions in gut-brain research.

What exactly is the gut-brain axis? How are the two systems connected? Can the microbes in our intestines really affect our minds?

“There are several ways in which [gut] microorganisms can influence the brain,” Karina Alviña, PhD, a research assistant professor of neuroscience at the University of Florida who was not involved in the study, told Verywell.

The Mind-Body Connection

Scientists used to mainly link depression to problems with certain neurotransmitters in the brain (like serotonin), stress hormones, or sleep.

Guillaume Méric, PhD , a microbiologist and a bioinformatician at Baker Heart & Diabetes Institute in Melbourne, Australia, and one of the study’s authors, told Verywell that we need to change how we think about mental health conditions.

According to Méric, conditions we associated with the mind, like depression, need to be thought of as being more intimately connected and influenced by other organ systems.

Méric said that research has shown that patients with severe mental health conditions often have very different microbes in their guts than people who do not have the conditions. According to Méric, these findings show “that our gut and our brain are intimately connected.”

That means that our diets and immune systems factor into our mood and other brain processes.

A Complex Loop

According to Alviña, there are trillions of microorganisms living in our gastrointestinal tract. Most are bacteria, but some are fungi and viruses.

These microbes digest what we eat by taking out the nutrients and other molecules to create metabolites, which we need to survive.

The Gut's Nervous System

The gut-brain axis is more of a loop than a one-sided relationship. Each end informs the other using three main paths.

Méric said that the gut actually has its own nervous system. It’s called the enteric nervous system (ENS). If it had to, the ENS could function independently of the central nervous system (CNS), which includes the brain. That’s why the ENS is sometimes called our “second brain.”

Alviña said that for a long time, researchers just saw the gut as being necessary for digestion.

Now, we know that gut microorganisms can influence the brain in at least three ways:

• The bloodstream: Gut bacteria produce and release certain metabolites that enter the blood circulation and interact with our immune system.
• The enteric nervous system : Certain metabolites affect the brain cells ( neurons ) that control gut function (the ENS).
• The vagus nerve : Some gut microbes “talk” with the brain through the vagus nerve , which connects the organs of the peripheral nervous system (like the intestines) with the CNS.

Neurotransmitters: From Gut to Brain

The gut and brain use these pathways to stay in constant communication.

According to Méric, most of the neurotransmitters that eventually work in the brain are made in the intestines. For instance, the ENS can produce and store around 90% of our total serotonin and 50% of our total dopamine.

Méric said these neurotransmitters are “famously involved in complex modulation of mood, reward, cognition, and other physiological and psychological processes.”

In broad terms, Méric said that means that having “a healthy gut is strongly linked to better psychological outcomes.”

The Gut and Depression

Depression has long been thought to be caused by an interplay of genetic, environmental, and biological factors.

While that’s not wrong, it’s also not completely right. Méric said that the gut microbiota is a whole new area for investigating what causes depression.

For example, research is showing that people with depression and other mental health disorders have very different gut microbiomes from people who don’t have these conditions.

Going back to the recent study, those findings supported previous research suggesting that inflammation caused by a gut bacterium called Morganella might influence depression.

Pathways to the Brain

The ways that the gut bacteria have been found to influence the brain—and vice versa—are along the same lines as the gut-brain axis:

• Gut bacteria can change which neurotransmitters are in the bloodstream, and inflammatory molecules produced in the gut can also play a role.
• The ENS—or “second brain”—makes neurotransmitters that are known to play a role in depression, such as serotonin.
• What happens in the gut can also stimulate the vagus nerve, which sends messages to the brain.

While the details have yet to be revealed, the pathways and factors that inform the gut-brain axis are becoming clearer.

An Integrated Approach to Health

Méric said that the gut-brain axis does not exist in a vacuum. Everything else that goes on in a person’s life also influences both their gut and mental health.

“It is always very hard to untangle cause and effect in these correlations,” Méric said.

The presence—or absence—of different bacteria depends on many factors, like a person’s diet and overall health. The authors of the study felt similarly.

They wrote that “taken together, our findings highlight the intimate influence of the gut-brain axis on humans.”

However, the researchers also acknowledged that “more mechanistic studies” are needed to “untangle and further interpret these predictions.”

“There is still so much to uncover,” Alviña said. “We are just starting to get a picture of how much the gut microbiome can influence the rest of the body, including the brain. Which, for the longest time, was considered to be isolated.”

Karina Alviña, PhD

We are just starting to get a picture of how much the gut microbiome can influence the rest of the body.

According to Alviña, future research will look at the relationship between different combinations of bacteria. They’ll also look at other physiological and pathophysiological conditions.

Similarly, there is the need for a better understanding of which metabolites are produced in the gut and how they get to the brain.

“We are still a long way from the promise of ‘precision medicine’ applied to gut health,” Méric added. “Because the gut microbiome is incredibly complex and variable between individuals and populations, we are still at the early stages of understanding this.” While researchers are just starting to discover links between gut microbiomes and depression, Méric said that “we do not yet understand very well how to manipulate our gut microbiome to resolve these health issues in general.”

What This Means For You

Researchers are learning more about the gut-brain connection. The microbes in your gut may affect your physical and mental health. Taking care of your gut by eating a varied diet with plenty of fiber can support your overall health.

Supporting Your Gut

Whether having your favorite food boosts your mood or you get “ hangry ” when you’ve gone too long without a meal, most of us have experienced the gut-brain connection.

In this way, Méric said that you can “trust your gut” and that it’s “unsurprising to know that our gastrointestinal system is one of our most advanced collection of organs after the brain.”

With that in mind, how can you support your gut health?

Alviña said that some research has shown that consuming specific combinations of bacteria called probiotics may help your mood. You can get probiotics from fermented foods (like yogurt) or as a dietary supplement.

You can also get prebiotics , which is a source of food for your gut’s “good” bacteria. However, research is still a bit inconsistent on their benefits.

There may not be a gut microbiome cure-all, but there are some evidence-backed ways to support your gut health. Méric said that “observational studies seem—perhaps unsurprisingly to most—to suggest the usual positive effects of a balanced diet, regular exercise, and sleep on general health.”

That diet should include plenty of fiber , which “had very positive health effects all around,” according to Méric.

Pennisi E. Gut microbe linked to depression in large health study . Science . Published online February 4, 2022. doi:10.1126/science.ada0998

Qin Y, Havulinna AS, Liu Y, et al.  Combined effects of host genetics and diet on human gut microbiota and incident disease in a single population cohort . Nat Genet.  2022;54(2):134-142. doi:10.1038/s41588-021-00991-z

Chen Y, Xu J, Chen Y. Regulation of neurotransmitters by the gut microbiota and effects on cognition in neurological disorders . Nutrients . 2021;13(6):2099. doi:10.3390/nu13062099

Bembnowska M, Jośko-Ochojska J. What causes depression in adults? . Pol J Public Health . 2015;125(2):116–120. doi:10.1515/pjph-2015-0037

By Sarah Simon Simon is a bilingual multimedia journalist specializing in health, science, culture, and technology. She is a PhD candidate in clinical psychology.

• Gut-Brain Connection

Updated 17th April 2024

Does gut health affect depression, and can your diet help?

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Your gut microbiome — which is the collection of trillions of bacteria, fungi, and other microbes in your gut — is crucial for your well-being, including your mental health. If you or someone you love are dealing with depression, it may be helpful to know that the latest evidence suggests a link between gut health and depression. 

For example, recent studies have found a connection between specific gut microbes and depression .

Meanwhile, a review of currently available data has suggested that changing the gut microbiome could be an avenue for reducing symptoms of depression and anxiety. 

But how exactly do the bacteria in your gut affect mental health, and can a specific diet help improve mental health issues like depression and anxiety? 

Let’s have a look at the research behind the gut-brain connection and how the food you eat could affect your mental health.

The gut-brain connection

Your brain and gut are linked by a two-way communication system called the gut-brain axis . 

The gastrointestinal tract is not just a long tube through which food is digested. It has its own complex nervous system called the enteric nervous system (ENS), which explains why we refer to the gut as our “second brain.” 

The gut-brain axis connects the ENS and central nervous system (CNS), allowing your gut to communicate with the brain, and vice versa. 

But how do these two organs communicate? Research suggests the gut microbiome may affect the brain in three main ways: 

Vagus nerve pathway : Chemicals produced by gut bacteria can send signals to your brain through the vagus nerve , which runs from your colon to your brain.

Neuroendocrine pathway : Some gut bacteria produce an amino acid called tryptophan, an important building block for neurotransmitters like serotonin , which influence mood. 

Immunoregulatory pathway : Gut bacteria interact with your body’s immune system by communicating with immune cells. 

Does gut health affect depression?

There’s more and more evidence suggesting that gut health may have a role in managing and even preventing mental health issues like depression. 

Research shows that people with depression have different gut microbes from people without depression. 

A 2019 observational study found that people with depression had depleted levels of Coprococcus and Dialister , compared with people who reported a higher quality of life. Those with depression also had bacteria associated with Crohn’s disease. 

A separate study found lower levels of the bacteria Bifidobacterium and Lactobacillus in people with depression, compared with those without.

To investigate the influence of the gut microbiome on depression, researchers have also looked into whether fecal microbiota transplants (FMT) can affect mental health. 

One systematic review looking at the effect of FMT on symptoms of mental health conditions — like depression — observed that FMT from donors without a mental health condition to someone living with a mental health condition relieved symptoms.

Meanwhile, FMT from donors with mental health conditions to those without could induce symptoms.

Experts are still trying to figure out how the gut microbiome affects depression, but one main theory involves serotonin. 

Serotonin is a neurotransmitter — a chemical messenger — that helps regulate mood and promotes feelings of happiness. Research shows the gut microbiome can influence levels of serotonin , which scientists have long linked to depression. 

However, a possible link between the gut microbiome and serotonin production would only be part of the puzzle. More so, experts have recently started to reevaluate the role serotonin plays in depression .

Can changing your diet help with depression?

There’s growing evidence that our diet could have a crucial effect on our mental health, thanks to its effect on the gut microbiome — a field of research known as psychobiotics. 

Following specific diets could even reduce the risk of developing depression. A 2018 systematic review concluded that people who followed the Mediterranean diet had a 33% lower risk of depression than people who did not. 

A separate study examined whether diet could improve symptoms of depression. The SMILES trial was a 12-week randomized control trial of people with major depressive disorder. 

These study participants were split into two groups and randomly assigned either personalized nutritional consulting sessions or social support counseling. 

At the end of the study, 32% of the diet group were considered to be in remission from depression, compared with just 8% in the counseling group. The trial also found that the more the participants improved their diet, the more their depression improved. 

Those in the diet group increased their consumption of fruits and vegetables, whole grains, nuts and seeds, fish, and healthy fats while reducing their intake of processed foods — dietary patterns in line with the Mediterranean diet .

Although this was another small-scale study — and some of the participants in each group were taking antidepressants throughout the study — the results are promising.

They provide a valuable jumping-off point for evidence on how diet can help with depression and the role of the gut-brain axis. 

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Meanwhile, a 2017 paper published in the journal Nutritional Neuroscience outlined five dietary recommendations to prevent depression based on current evidence:

following “traditional” dietary patterns like the Mediterranean, Norwegian, or Japanese diets

increasing your intake of fruits, vegetables, legumes, wholegrain cereals, nuts, and seeds

increasing your intake of foods rich in omega-3 polyunsaturated fatty acids

replacing unhealthy foods with wholesome nutritious foods

limiting your intake of processed foods, fast food, commercially baked goods, and sweets

The study authors stressed that these recommendations aren’t set in stone and could change if the scientific evidence evolves. 

At ZOE, we know that everyone’s gut microbiome and responses to particular foods are different.

ZOE scientists and their colleagues, who run the largest nutritional study of its kind, recently identified 15 “good” gut bugs that are linked to good health. They also found 15 “bad” bugs that are indicators of poor health. 

Take our free quiz to learn how you can discover which of the 15 good and bad bugs live in your gut, as well as your personal “gut boosters” and “gut suppressors,” so you can eat more of the right foods for your unique microbiome.

'Leaky gut syndrome' and depression

A gastrointestinal disorder called “leaky gut syndrome” has been gaining more and more notoriety, and some people have linked it to depression, but it’s important to note that there is little evidence for this link.

Leaky gut syndrome is a phenomenon where toxins and bacteria supposedly “leak” through the intestinal lining into the bloodstream, causing the onset of unpleasant symptoms like bloating, cramping, and mood swings. 

The lining of your intestine is made of tightly packed junctions that control what is absorbed into the intestine, acting as a physical barrier to prevent any unwanted substances from entering the bloodstream. 

A small level of gut permeability is considered normal, but in some people — like those with Crohn's and celiac disease — this protective barrier is compromised, known as increased intestinal permeability . 

Proponents of leaky gut syndrome believe it’s the underlying cause of all sorts of conditions, including everything from migraines and psoriasis to food sensitivities, fibromyalgia, multiple sclerosis, autism, and even depression. 

Most of these claims haven’t been proven , and mainstream medicine doesn’t recognize leaky gut syndrome as a real diagnosis.

There isn’t any real evidence to suggest leaky gut syndrome is the cause of disease, but rather experts think increased gut permeability could be a symptom of some illnesses. 

So, where did the link between leaky gut syndrome and depression come from? One very small preliminary study found biomarkers of gut permeability in patients with a history of suicidal behavior or depression. 

The study authors concluded that ​​leaky gut syndrome could explain the role of inflammation in depression or suicidal behavior, but they couldn’t find any definite causal link. 

The study had several limitations. Aside from a very small sample size, the researchers even concluded that their results were probably affected by variables like smoking, alcohol intake, and dietary habits — all of which can affect your gut health.

Until more research is done on the role of gut permeability in disease, we can’t confidently say that leaky gut syndrome is a valid condition, nor that it’s linked to depression. 

Although the scientific evidence is still young, existing research on gut health and depression shows there’s a link between your gut bacteria, what you eat, and your mental health. 

What we know so far about the gut-brain axis could help support the theory that following a diet that supports gut health could be helpful in managing and preventing depression. 

A diet rich in fruits, vegetables, whole grains, and healthy fats could reduce the risk of depression, but the research is still emerging.

There still isn’t enough evidence to prove a causal link between the gut microbiome and depression, so we should be cautious about using food as the only treatment tool for the condition.

If you’d like to learn more about how to eat the right foods for your unique gut microbiome, check out ZOE’s at-home testing kit .

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A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). (2017). 

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Dietary recommendations for the prevention of depression. (2016). 

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Effect of fecal microbiota transplant on symptoms of psychiatric disorders: a systematic review. (2020).

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Healthy dietary indices and risk of depressive outcomes: a systematic review and meta-analysis of observational studies. (2018). 

https://www.nature.com/articles/s41380-018-0237-8  

Influence of Tryptophan and Serotonin on Mood and Cognition with a Possible Role of the Gut-Brain Axis. (2015).

https://www.mdpi.com/2072-6643/8/1/56/htm?source=post_page

Interaction between microbiota and immunity in health and disease. (2020).

https://www.nature.com/articles/s41422-020-0332-7  

​​Intestinal permeability defects: is it time to treat? (2013). 

https://pubmed.ncbi.nlm.nih.gov/23851019/  

Leaky gut biomarkers in depression and suicidal behavior. (2018). 

https://onlinelibrary.wiley.com/doi/full/10.1111/acps.12978  

Neurotransmitter modulation by the gut microbiota. (2019). 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6005194/  

Possible association of Bifidobacterium and Lactobacillus in the gut microbiota of patients with major depressive disorder. Journal of affective disorders . (2016).

https://pubmed.ncbi.nlm.nih.gov/27288567/

The Expanded Biology of Serotonin. (2018). 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5864293/  

The Gut-Brain Axis: The Missing Link in Depression. (2015). 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4662178/  

The neuroactive potential of the human gut microbiota in quality of life and depression. (2019). 

https://www.nature.com/articles/s41564-018-0337-x  

Vagus Nerve as Modulator of the Brain–Gut Axis in Psychiatric and Inflammatory Disorders. (2018). 

https://www.frontiersin.org/articles/10.3389/fpsyt.2018.00044/full  

What has serotonin to do with depression? (2015). 

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This paper is in the following e-collection/theme issue:

Published on 22.4.2024 in Vol 10 (2024)

Digital Dietary Behaviors in Individuals With Depression: Real-World Behavioral Observation

Authors of this article:

Original Paper

• Yue Zhu 1, 2 , PhD   ; 
• Ran Zhang 1, 2 , PhD   ; 
• Shuluo Yin 3 , MS   ; 
• Yihui Sun 3, 4 , MS   ; 
• Fay Womer 5 , MD   ; 
• Rongxun Liu 6 , MS   ; 
• Sheng Zeng 3, 4 , MS   ; 
• Xizhe Zhang 1, 3 * , PhD   ; 
• Fei Wang 1, 2 * , MD  

1 Early Intervention Unit, Department of Psychiatry, The Affiliated Brain Hospital of Nanjing Medical University, Nanjing, China

2 Functional Brain Imaging Institute of Nanjing Medical University, Nanjing, China

3 School of Biomedical Engineering and Informatics, Nanjing Medical University, Nanjing, China

4 School of Computer Science and Engineering, Northeastern University, Shenyang, China

5 Department of Psychiatry and Behavioral Sciences, Vanderbilt University Medical Center, Nashville, TN, United States

6 Henan Key Laboratory of Immunology and Targeted Drug, Henan Collaborative Innovation Center of Molecular Diagnosis and Laboratory Medicine, School of Laboratory Medicine, Xinxiang Medical University, Xinxiang, China

*these authors contributed equally

Corresponding Author:

Xizhe Zhang, PhD

Early Intervention Unit

Department of Psychiatry

The Affiliated Brain Hospital of Nanjing Medical University

264 Guangzhou Road, Gulou District, Nanjing City, China

Nanjing, 210000

Phone: 1 86 02583295953

Fax:1 86 02583295953

Email: [email protected]

Background: Depression is often accompanied by changes in behavior, including dietary behaviors. The relationship between dietary behaviors and depression has been widely studied, yet previous research has relied on self-reported data which is subject to recall bias. Electronic device–based behavioral monitoring offers the potential for objective, real-time data collection of a large amount of continuous, long-term behavior data in naturalistic settings.

Objective: The study aims to characterize digital dietary behaviors in depression, and to determine whether these behaviors could be used to detect depression.

Methods: A total of 3310 students (2222 healthy controls [HCs], 916 with mild depression, and 172 with moderate-severe depression) were recruited for the study of their dietary behaviors via electronic records over a 1-month period, and depression severity was assessed in the middle of the month. The differences in dietary behaviors across the HCs, mild depression, and moderate-severe depression were determined by ANCOVA (analyses of covariance) with age, gender, BMI, and educational level as covariates. Multivariate logistic regression analyses were used to examine the association between dietary behaviors and depression severity. Support vector machine analysis was used to determine whether changes in dietary behaviors could detect mild and moderate-severe depression.

Results: The study found that individuals with moderate-severe depression had more irregular eating patterns, more fluctuated feeding times, spent more money on dinner, less diverse food choices, as well as eating breakfast less frequently, and preferred to eat only lunch and dinner, compared with HCs. Moderate-severe depression was found to be negatively associated with the daily 3 regular meals pattern (breakfast-lunch-dinner pattern; OR 0.467, 95% CI 0.239-0.912), and mild depression was positively associated with daily lunch and dinner pattern (OR 1.460, 95% CI 1.016-2.100). These changes in digital dietary behaviors were able to detect mild and moderate-severe depression (accuracy=0.53, precision=0.60), with better accuracy for detecting moderate-severe depression (accuracy=0.67, precision=0.64).

Conclusions: This is the first study to develop a profile of changes in digital dietary behaviors in individuals with depression using real-world behavioral monitoring. The results suggest that digital markers may be a promising approach for detecting depression.

Introduction

The mental health of students has become the forefront of concerns, particularly since the onset of the COVID-19 pandemic. Approximately 45% of college students in China reported experiencing mental health issues during the outbreak [ 1 ]. Depression screening typically involves self-reported data, but there is a lack of objective markers to promptly identify individuals experiencing depression. Early identification and intervention are crucial for mitigating the impact of depression during critical periods for the academic and occupational functioning of students [ 2 ].

Appetite disturbance or changes in dietary behaviors are common symptoms of depression and may serve as objective indicators of the condition in a large population [ 3 ]. Dietary behavior can exert an influence on mental health through a variety of pathways, including circadian rhythms, oxidative stress, and the gut microbiota [ 4 ]. Based on the time of meals, intervals between meals, daily eating window, and food intake of the day, dietary behavior patterns can be categorized into morningness, intermediate, and eveningness chronotypes [ 5 ]. Eveningness chronotype commonly exhibits a higher tendency to skip breakfast, eat dinner later, and allocate a greater proportion of their daily food intake to later hours of the day [ 6 ]. Prior research has additionally demonstrated that the eveningness chronotype, coupled with social jetlag, constitutes a risk factor for depression [ 7 , 8 ]. Besides, individuals with more pronounced fluctuations in their eating windows often display heightened emotional vulnerability [ 9 ]. However, previous studies of diet relied on retrospective questionnaires or interviews, which may fail to accurately reflect real-world behavior [ 10 ]. Additionally, these methods typically assess only 1 aspect of dietary behavior, such as diet quality or eating habits [ 8 , 11 , 12 ]. To fully understand dietary behaviors, it is necessary to use multiple scales to assess multiple dimensions, such as diet quality, emotional eating, and chronotype of eating habits. However, using multiple scales can lead to participants taking too long to complete the questionnaire, reducing its validity. Furthermore, understanding daily behavior features requires repeated behavioral monitoring over an extended period, while retrospective reports from a single point in time may not accurately reflect true behavior [ 13 ].

The use of electronic platforms for behavioral monitoring allows for real-time assessment of human behavior and can trigger an alert if measured behavior deviates from healthy norms [ 14 , 15 ]. Additionally, these platforms enable the collection of large amounts of high-frequency, high-dimensional continuous data, which can be used to identify typical multidimensional behavior features over an extended period based on naturalistic situations [ 16 , 17 ]. The growing body of literature leveraging behavioral monitoring for depression prediction has gained traction, spurred by the profound shifts in lifestyle behavior patterns, especially during the COVID-19 pandemic [ 18 - 20 ]. Nonetheless, predominant inquiries have predominantly concentrated on probing the correlation between physical activity, social network engagement, and mental well-being facilitated through mobile devices [ 21 - 23 ]. However, an evident void persists in comprehensively exploring the nexus between the surveillance of dietary behavior patterns and depression. On university campuses, meals are often paid for using electronic transactions linked to a student account, providing the opportunity to collect digital dietary behavior data. In this study, real-world monitoring was used to track dietary behavior for a month, and data on time, expenditure, and location patterns were collected.

To the best of our knowledge, this is the first study to use electronic device–based behavioral monitoring instead of retrospective self-reported data to examine the digital dietary behaviors of individuals with depression compared with controls, and to investigate the relationship between these behaviors and depression. It is common for depression to occur alongside other symptoms, but the relationship between digital dietary behaviors and these comorbid symptoms of depression remains underexplored. Therefore, we also aim to determine whether these comorbid symptoms are associated with dietary behaviors and to clarify the role these symptoms play in the relationship between changes in dietary behavior and depression. The final data analysis will involve using digital dietary behavior features to detect depression.

Recruitment of Participants

A total of 3678 medical students from Xinxiang Medical University willingly engaged in this study, responding to the institution’s mental health survey notification. As part of this engagement, they underwent a cross-sectional mental status survey from October 6 to 12, 2020. Concurrently, during the survey, these participants also consented to furnish records of their eating behaviors for the period spanning from October 1 to 31, 2020. These records were sourced from electronic transactions linked to their respective student accounts. All participants completed questionnaires via WeChat (Tencent Corp) and signed web-based informed consent.

Web-Based Measurements

Basic sociodemographic characteristics, such as gender, age, BMI, and educational level, were collected using the WeChat official account platform. All participants also completed the following psychological assessments: the Patient Health Questionnaire-9 (PHQ-9), the Generalized Anxiety Disorder Questionnaire-7 (GAD-7), the Perceived Stress Scale-14 (PSS-14), and the Insomnia Severity Index (ISI). All the details of these psychological assessments can be found in Multimedia Appendix 1 .

Study Participants and Inclusion Criteria

Based on the outcomes of the psychological survey, the inclusion criteria for the mild depression group, the moderate-severe depression group, and the healthy control (HC) group, as well as the exclusion criteria, were defined as follows.

Inclusion criteria were established as follows: individuals in the mild depression group had PHQ-9 scores between 5 and 9, while those in the moderate-severe depression group had PHQ-9 scores of 10 or higher. The HC group had PHQ-9 scores below 5, GAD-7 scores below 5, PSS-14 scores below 29, and ISI scores below 8. Exclusion criteria for all participants included PHQ-9 scores below 5 and any of the following conditions: GAD-7 scores of 5 or higher, PSS-14 scores of 29 or higher, or ISI scores of 8 or higher. The participant inclusion process for this study is depicted in Figure 1 (Step 1).

Ethical Considerations

Prior to their involvement in the study, all participants provided their informed consent through a formally endorsed consent form. The study was approved by the Biomedical Ethics Committee of Xinxiang Medical University (XYLL-2020235).

Dietary Data Collection

During the COVID-19 pandemic in China, students were required to stay on campus, resulting in most students eating at the campus cafeterias on a daily basis. These meals are often paid for using electronic transactions linked to a student’s account, and there are 3 cafeterias at the school. The dietary data preprocess can be found in Multimedia Appendix 1 . Previous studies have shown that diet time, or chronotype, is related to circadian rhythms and mood [ 5 ], and location and periodicity of meals are related to depression symptoms [ 24 ]. Therefore, we evaluated 6 dietary behavior features, including time, location, expenditure, daily dietary items and frequency of meals, and all-day dietary behavior patterns, to objectively assess dietary behaviors in relation to depression in this study ( Figure 1 , Step 2).

Calculation of Dietary Features

Time patterns.

To determine the number of daily meals, we counted the number of records starting from the first recorded meal. Dietary behaviors within 2 hours of this initial record were part of a single meal, which could be further divided into up to 1, 2, or 3 meals per day: breakfast, lunch, and dinner. In addition, based on the cafeteria’s hours of operation, the 3 meals are divided into time slots as follows: breakfast from 6:30 AM to 8:30 AM, lunch from 11 AM to 1 PM, and dinner from 5:30 PM to 7:30 PM. If there were multiple electronic transactions within a single meal, we used the timestamp of the first transaction as the time of the meal for analysis.

Time Intervals Between Meals

We used the times of breakfast, lunch, and dinner calculated from the time patterns to determine the time intervals between each pair of meals: breakfast and lunch, lunch and dinner, and breakfast and dinner.

Expenditure on Meals

After dividing meals into breakfast, lunch, and dinner based on the time patterns, we calculated the total cost for each meal by summing up multiple electronic transactions for a single meal. Expenditure on a single meal may indicate an individual’s appetite as it reflects the amount of food purchased.

Location Patterns

To determine location patterns of dietary behavior, we calculated the frequency of visits to each cafeteria by counting total number of cafeterias visited in October and calculated the frequency of the student’s visits to the cafeteria for breakfast, lunch, and dinner using the following formula:

Daily Dietary Diversity and Frequency of Meals

The average number of different foods consumed per day in October was calculated as a measure of food diversity. The frequency of breakfast, lunch, and dinner in the month was also calculated as a measure of dietary habits. These measures were used to understand the dietary behaviors of participants in the study.

All-Day Dietary Behavior Patterns

People may have regular or irregular dietary behavior patterns, such as consistently or selectively eating breakfast, lunch, and dinner. There are 7 possible dietary behavior patterns: eating only breakfast, only lunch, only dinner, breakfast-lunch, lunch-dinner, and all 3 meals (breakfast-lunch-dinner pattern). All-day dietary behavior patterns are defined as the meals eaten by a participant on a given day. The frequency of a participant’s daily dietary behavior patterns can be calculated based on their dietary records for the entire month of October. To do this, the daily records are taken as a unit and the frequency of each dietary behavior pattern is calculated using the following formula:

Statistical Indices of Dietary Features

Statistical indices were calculated for dietary features such as time patterns, intervals between meals, and expenditure on meals, including mean, median, median absolute deviation (MAD), and maximum and minimum values for the entire month of October. The study also separated weekday and weekend behavior by calculating dietary features separately for the 2 time periods. More information can be found in Table S1 in Multimedia Appendix 1 .

Statistical Analysis

ANOVA and chi-square tests were used to analyze demographic and psychological characteristics. ANCOVA (analyses of covariance) was used to compare dietary behavior features among groups, with age, gender, BMI, and educational level as covariates. All variables in the 6 dietary features were transformed into Z-scores to give equal weight and minimize the impact of outliers in the study. Logistic regression analyses were used to examine associations between all-day dietary behavior patterns and depression severity (mild depression, and moderate-severe depression), as well as associations between other psychological symptoms in depression groups or all participants and all-day dietary behavior patterns, with age, gender, BMI, and educational level as covariates. The all-day dietary behavior patterns were categorized into tertiles: Rare (less than 1 SD), Normal (within 1 SD), and Always (more than 1 SD) in logistic regression analyses. Mediation analysis was performed using Model 4 with 1 independent variable (all-day dietary behavior patterns), 1 dependent variable (groups), and 1 moderator (other psychological symptoms) in the PROCESS. A bootstrapping procedure with 95% CIs was used to measure the moderating effect, with 5000 bootstrap samples. Age, gender, BMI, and educational level were included as covariates in the model. All analyses were conducted using SPSS (version 25.0; IBM Corp).

Classification Model

We analyzed changes in dietary behaviors between individuals with HC and depression to detect depression. These dietary behaviors were divided into tertile levels (HC, mild depression, and moderate-severe depression) and binary levels (HC and moderate-severe depression). We used a support vector machine with a radial basis function kernel as the classifier and selected the optimal parameters (0.1 for C and 0.001 for gamma) through grid search. These same parameters were used in all subsequent experiments. To avoid overfitting the model and ensure the accuracy of our results, we used 5-fold cross-validation and divided the training and validation sets in a 4:1 ratio.

Demographic and Clinical Characteristics of Participators

A total of 3310 students, consisting of 2222 HC, 916 mild depression, and 172 moderate-severe depression, met the inclusion criteria and were ultimately included in the study. And 368 students exhibited psychological symptoms, notably anxiety, insomnia, or abnormal stress, while concurrently not manifesting depressive symptoms. As a result, they were excluded from the study cohort. In the students with mild depression, the following rates were observed: 37.7% (n=345) with anxiety, 17.8% (n=163) with perceived abnormal stress, and 23.8% (n=218) with insomnia. In moderate-severe depressive students, the corresponding percentages were: 75% (n=129) with anxiety, 70.3% (n=121) with perceived abnormal stress, and 53.5% (n=92) with insomnia. The demographic and clinical characteristics of the participants can be found in Table 1 .

a HC: healthy control.

b N/A: not applicable.

c Information that was missing for some participants.

d PHQ-9: Patient Health Questionnaire-9.

e GAD-7: Generalized Anxiety Disorder Questionnaire-7.

f PSS-14: Perceived Stress Scale-14.

g ISI: Insomnia Severity Index.

Dietary Features Among HC, Mild Depression, and Moderate-Severe Depression

The ANCOVA analyses showed that there were significant differences between the groups in terms of time patterns, the intervals between meals, expenditure on meals, daily dietary diversity and frequency of meals, and all-day dietary behavior patterns (details in Table S2 in Multimedia Appendix 1 ). There was no significant difference in location patterns among the 3 groups.

In terms of time patterns, post hoc analyses showed that compared with mild depression and HC, moderate-severe depression had significantly increased MAD of lunchtime ( P =.04 and P =.004, separately), latest lunchtime ( P =.02 and P =.007, separately) and MAD of dinner time ( P =.02 and P =.01, separately) on weekdays, and there was no significant difference between mild depression and HC ( Figure 2 A). In terms of time intervals between meals, post hoc analyses that compared mild depression and HC, moderate-severe depression had increased MAD ( P =.001 and P <.001, separately) and maximum ( P =.02 and P =.005, separately) time intervals between lunch and dinner on weekdays, respectively, but mild depression and HC had no significant difference with each other ( Figure 2 B). On weekends, post hoc analyses that compared with HC, mild depression had a significant decrease in the mean time interval between breakfast and lunch ( P =.01), while mild depression and moderate-severe depression had significant decreases in the maximum time interval between breakfast and lunch ( P =.02 and P =.03 separately; Figure 2 B). The MAD of lunchtime on weekdays was higher in moderate-severe depression (18 minutes 58 seconds) than mild depression (17 minutes 38 seconds) and HC (17 minutes 5 seconds). Similarly, the MAD of dinner time on a weekday was higher in moderate-severe depression (26 minutes 11 seconds) than in mild depression (23 minutes 39 seconds) and HC (23 minutes 26 seconds). Additionally, the MAD time interval between lunch and dinner on weekdays was larger in moderate-severe depression (34 minutes 20 seconds) than in mild depression (29 minutes 25 seconds) and HC (29 minutes 23 seconds; Table S2 in Multimedia Appendix 1 ). These findings indicate a temporally erratic lunch and dinner dietary pattern in moderate-severe depression.

In terms of expenditure on meals, compared with HC, both students with mild and moderate-severe depression had significant increases in the mean ( P =.02 and P =.02, separately) and median ( P =.002 and P =.006, separately) of dinner expenditure on weekdays ( Figure 2 C). However, there was no significant difference between mild depression and moderate-severe depression. On weekends, the mild depressive students had a significant increase in the minimum lunch expenditure compared with HC ( P =.03) and moderate-severe depression ( P =.01), but HC and moderate-severe depression had no significant difference from each other ( Figure 2 C).

In terms of daily dietary diversity, post hoc analyses that moderate-severe depression had significant decreases compared with mild depression and HC both on weekdays ( P =.02 and P =.01, separately) and weekends ( P =.03 and P =.01, separately). However, there was no significant difference between mild depression and HC. We also found that compared with HC, moderate-severe depression had a significant reduction in breakfast frequency on weekdays ( P =.02) and weekends ( P =.005). Additionally, compared with mild depression, moderate-severe depression had a significant reduction in breakfast frequency on weekends ( P =.05). However, there was no significant difference between mild depression and HC in breakfast frequency on weekdays and weekends ( Figure 2 D).

Finally, in terms of all-day dietary behavior patterns, compared with HC and mild depression, moderate-severe depression had a reduction in the breakfast-lunch-dinner pattern on weekdays ( P =.001 and P =.002, separately) and enrichment in the lunch-dinner pattern on weekdays ( P =.005 and P =.03 separately; Figure 2 E). However, there was no significant difference between HC and mild depression. On weekends, we observed that moderate-severe depression had an enrichment in the lunch-dinner pattern compared with HC ( P =.008; Figure 2 E).

Associations Between All-Day Dietary Behavior Patterns and Depression

To gain a deeper understanding of the relationship between comprehensive indicators of all-day dietary behavior patterns and depression severity. Using multiple logistic regression, we analyzed the associations between alterations in all-day dietary behavior patterns and depression severity in Figures 3 A and 3B. After adjusting for age, gender, BMI, and educational level, we found that the Normal and Always lunch-dinner patterns on weekdays were positively associated with mild depression (Exp(B), 95% CI 1.360, 1.050-1.761; 1.460, 1.016-2.100; respectively), and the Always breakfast-lunch-dinner pattern on weekdays was negatively associated with moderate-severe depression (Exp(B), 95% CI 0.467, 0.239-0.912). The comparison of tertile levels of these all-day dietary behavior patterns among 3 groups can be found in Table S3 in Multimedia Appendix 1 , and the percent of tertile levels of these all-day dietary behavior patterns can be found in Multimedia Appendix Figure S1.

Associations Between All-Day Dietary Behavior Patterns and Other Clinical Symptoms

Our findings revealed a positive correlation between anxiety and adherence to the consistent always breakfast-lunch-dinner pattern on weekdays among individuals with depression as well as all participants ( Figures 3 C and 3D). However, no significant associations were discovered between other all-day dietary patterns and other clinical symptoms (Table S4 in Multimedia Appendix 1 ). In the mediation model, anxiety served as a mediator ( R 2 =0.570, P <.001). A bootstrapped 95% CI confirmed that the indirect effect of groups (HC, mild depression, and moderate-severe depression) had an impact of 0.042 that was produced by anxiety as a mediator on breakfast-lunch-dinner pattern ( Figure 3 E).

The Detection of Dietary Patterns for Depression

Our results showed that alterations in dietary behaviors of depression had an accuracy of 0.53, F 1 -score of 0.52, precision of 0.60, recall of 0.62, and an area under curve of 0.59 for detecting mild depression and moderate-severe depression. For detecting moderate-severe depression specifically, the accuracy was 0.67, F 1 -score was 0.60, precision was 0.64, recall was 0.65, and area under curve was 0.69 ( Table 2 ).

a AUC: area under the curve.

b HC: healthy control.

Principal Results

This study is the first to investigate digital dietary patterns of individuals with mild and moderate-severe depression using electronic device–based monitoring. The results indicate that individuals with moderate-severe depression exhibit more irregular eating time patterns, greater fluctuations in their feeding window, higher expenditure on dinner, lower food diversity, and a decreased frequency of consuming breakfast, as well as more irregular lunch-dinner patterns and less regular breakfast-lunch-dinner patterns compared with HC. The study also found that maintaining a regular breakfast-lunch-dinner pattern is negatively associated with moderate-severe depression, and maintaining an irregular lunch-dinner pattern is positively associated with mild depression. Additionally, the presence of anxiety is positively associated with the breakfast-lunch-dinner pattern, and the severity of anxiety has an indirect effect on the relationship between depression and the breakfast-lunch-dinner pattern. Importantly, the study suggests that digital dietary features can be used to detect depression, particularly moderate-severe depression, indicating that quantified digital behavior could be a promising approach to the detection of depression.

Comparison With Prior Work in Dietary Behavior of Depression

We found that individuals with moderate-severe depression exhibited a reduction in dietary diversity, a decreased frequency of consuming breakfast, and irregular timing for lunch and dinner. The loss of interest in pleasurable activities, including eating, is a core symptom of depression, which may explain the decreased dietary diversity in individuals with moderate-severe depression. The findings of decreased breakfast frequency in moderate-severe depression align with previous research, which has identified a significant association between skipped or infrequent breakfast and an increased risk for depression [ 25 , 26 ]. The frequency of lunch and dinner did not significantly contribute to depression [ 26 , 27 ]. This discrepancy may be attributed to the fact that individuals with depression tend to have worse moods in the morning, which may negatively impact their appetite for breakfast. Considering these findings, it is important to consider the specific meal that is skipped when implementing dietary interventions to prevent depression. The study found that individuals with mild and moderate-severe depression exhibited significant fluctuations in the timing of lunch and dinner, as well as an irregular time interval between these meals. These findings align with previous research that has identified the importance of the feeding window on mental health [ 28 , 29 ], with irregular eating time patterns being associated with an increased risk of mental health distress [ 30 ]. Additionally, this study is the first to investigate the expenditure on 3 meals in individuals with depression, which provides insight into their food intake and appetite for each meal. The results indicate that individuals with mild and moderate-severe depression spent more money on dinner, which is consistent with the observation that individuals with major depressive disorder tend to have higher food intake during dinner compared with breakfast and lunch [ 31 ]. Notably, this study is the first to report that depression is associated with a preference for higher expenditure on dinner, while also being accompanied by a low frequency of breakfast.

This study is the first to objectively quantify all-day dietary behavior patterns by integrating time patterns, frequency of meals, and other parameters, and it revealed that moderate-severe depression is associated with an increase in lunch-dinner patterns and a decrease in breakfast-lunch-dinner patterns. Previous research has demonstrated that consuming breakfast, lunch, and dinner every day can reduce the prevalence of first-onset depression in a 5-year follow-up [ 32 ]. The lunch-dinner pattern is associated with eating later in the day and a meta-analysis has indicated that depressed patients are more inclined to spend on food later in the day, a phenomenon known as eveningness chronotype [ 33 ]. The relationship between eveningness chronotype and depressive symptoms aligns with pre-existing theories of chronobiology, which suggest that circadian dysfunction can have adverse effects on psychological well-being [ 34 , 35 ]. Eveningness chronotype is associated with a higher likelihood of regularly skipping or postponing breakfast [ 36 ] and it is well recognized that eating breakfast plays an important role in lowering blood cortisol levels and disturbances in glucose metabolism, which may affect serotonin levels [ 37 ].

Prior research in the dietary patterns field, whether dietary nutrition, dietary frequency, or dietary chronotype studies, predominantly relied on questionnaires [ 38 , 39 ]. The use of electronic behavioral monitoring for evaluating dietary behavioral patterns is still in its nascent technological phase. The self-monitoring is a prevalent method for assessing electronic dietary behaviors in the study of mental health [ 40 , 41 ]. This approach predominantly entails participants proactively documenting their daily dietary intake using an electronic device, often an app. However, it is important to acknowledge that excessive self-recording of behaviors could potentially lead to fatigue and monotony. While a frequency ranging from 2 to 3 times per week proved to be acceptable and reasonable [ 42 ], it once again harbors the inherent issue of recall bias that was previously encountered. Moreover, the field of wearable device-based monitoring for tracking dietary behavior has witnessed notable advancements [ 43 , 44 ]. However, its application in the field of psychiatry remains unexplored to date. The study marks the pioneering use of objective electronic device–based monitoring, unveiling anomalous eating patterns among individuals with depression.

The Associations Between Dietary Behavioral Patterns and Depression

The study found that maintaining a lunch-dinner pattern was positively associated with mild depression. Furthermore, maintaining a breakfast-lunch-dinner pattern was negatively associated with moderate-severe depression. These findings align with previous research that has identified eating breakfast as a health-promoting behavior [ 45 ] and a positive association between skipping breakfast and depressive symptoms [ 46 ]. Additionally, it highlights the importance of meal substitution for regular eating patterns as a positive association with emotional disorders [ 47 ]. Overall, these findings suggest that maintaining a regular dietary pattern can be considered a dietary strategy for depression prevention.

Furthermore, the study found that anxiety is positively associated with the breakfast-lunch-dinner pattern. We can infer from the result that individuals with anxiety tend to choose to regularly eat 3 meals in their daily life and that depression with increasing anxiety may lead to an increase in the breakfast-lunch-dinner eating behavior. Literature has also indicated that individuals with anxiety tend to engage in more overeating situations [ 48 ] and have a positive association between anxiety symptoms and emotional and external eating [ 49 ]. However, the study also indicates that those with depression tend to intake more in dinner and then postpone or skip breakfast the next day. The study also found that anxiety could mediate the relationship between depression and breakfast-lunch-dinner pattern, which indicates that students with anxiety tend to maintain a regular breakfast-lunch-dinner pattern rather than postponing or skipping breakfast. This highlights the need for careful consideration when implementing dietary interventions for the comorbidity of depression and anxiety.

The Potential Value of Digital Dietary Behaviors in Depression

This study is the first to use digital dietary behaviors based on real-world behavioral monitoring to detect mild depression and moderate-severe depression. The results indicate that digital dietary behaviors could distinguish between moderate-severe depression and HC. Depression is a disorder characterized by brain-based dysfunction that is expressed through behavioral changes. The diagnosis of depression traditionally relies on structured interviews or questionnaires, which are based on retrospective self-reports and the threshold scores of questionnaires. These methods can be prone to bias and subjectivity. The use of digital markers of continuous daily behavioral monitoring as an objective indicator to detect depression represents a promising supplementary approach [ 13 ].

In this study, students’ dietary behaviors were analyzed over a period of 1 month to draw a profile of dietary patterns in depression. This is the first exploration of the relationship between digital dietary behaviors and depression, and the use of digital dietary behaviors to detect depression. Another thing to watch out for is that the results indicate that a deep learning model of dietary behaviors from digital devices holds more accurate detection of moderate-severe depression than mild depression. This is likely due to the observation that moderate-severe depression presents more erratic dietary behaviors than mild depression and HCs. Overall, this study highlights the potential of digital dietary features as a promising manner in the detection of depression, particularly moderate-severe depression.

Limitations

There are several limitations in this study that should be acknowledged. First, the measurement of depression severity in this study was based on self-reported data, future studies should consider clinician-based rating scales to reduce bias. Additionally, this study used a cross-sectional survey of depression, which does not capture changes in symptomology over time. A longitudinal psychological survey combined with continuous daily behavioral monitoring could provide further insight into dietary progression markers related to the severity of depressive symptoms over time. Finally, the study did not assess daily dietary structure and nutrient intake.

Conclusions

This study represents a pioneering endeavor in objectively characterizing the digital dietary behaviors of individuals experiencing depression, using real-world monitoring as opposed to self-reported retrospective data. Our findings indicate that students with depression experience disruptions in various aspects, including time patterns, the intervals between meals, expenditure on meals, daily dietary diversity and frequency of meals, and all-day dietary behavior patterns. Notably, individuals with moderate-severe depression showcase greater irregularities in eating time patterns, fluctuated feeding windows, decreased food diversity, higher expenditure on dinner, and a preference for consuming only lunch and dinner. Furthermore, maintaining a regular breakfast-lunch-dinner eating pattern exhibits a negative correlation with moderate-severe depression. Keeping a lunch-dinner pattern is positively associated with mild depression. This research not only fills a critical gap in the existing academic literature but also sheds light on the promising potential of digital dietary behaviors as objective makers to the detection of depression, particularly moderate-severe depression.

Acknowledgments

This study was supported by grants from National Science Fund for Distinguished Young Scholars (81725005 to FW), NSFC-Guangdong Joint Fund (U20A6005 to FW), Jiangsu Provincial Key Research and Development Program (BE2021617 to FW), National Natural Science Foundation of China (62176129 to XZ), National Key Research and Development Program (2022YFC2405603 to XZ), and Henan Provincial Research and Practice Project for Higher Education Teaching Reform (2021SJGLX189Y to RL). The authors would like to thank all participants who took part in this study. The authors would also like to thank the support to recruitment by personnel at Xinxiang Medical University.

Data Availability

The data sets generated and analyzed during this study are available from the co-corresponding authors (FW: [email protected]; XZZ: [email protected]) on reasonable request.

Authors' Contributions

FW and XZZ are co-corresponding authors. XZZ and FW designed the study. RXL and YZ enrolled participants. YHS, YZ, SLY, and SZ analyzed data. YZ, RZ, and FYW wrote the paper.

Conflicts of Interest

None declared.

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Abbreviations

Edited by A Mavragani, T Sanchez; submitted 27.03.23; peer-reviewed by A Lamer, A Ghosh; comments to author 17.08.23; revised version received 02.09.23; accepted 01.03.24; published 22.04.24.

©Yue Zhu, Ran Zhang, Shuluo Yin, Yihui Sun, Fay Womer, Rongxun Liu, Sheng Zeng, Xizhe Zhang, Fei Wang. Originally published in JMIR Public Health and Surveillance (https://publichealth.jmir.org), 22.04.2024.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in JMIR Public Health and Surveillance, is properly cited. The complete bibliographic information, a link to the original publication on https://publichealth.jmir.org, as well as this copyright and license information must be included.

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5 Gut Facts Experts Want You to Know

We asked gastroenterologists every mortifying question we could think of. Here’s straight talk on constipation, heartburn and gas.

By Jancee Dunn

Flatulence, constipation and diarrhea can be embarrassing. But you don’t need to be shy about discussing them with a gastroenterologist, a doctor who treats conditions of the digestive system.

“We’ve heard it all,” said Sophie Balzora, a gastroenterologist and clinical professor of medicine at NYU Langone Health. “And we want to normalize talking about it.”

So I took her advice and plunged in, asking her and other experts what they want you to know about your gut.

Acid reflux and heartburn are not the same thing.

People often use the terms “acid reflux” and “heartburn” interchangeably, but it’s important not to mix them up, said Christine Lee, a gastroenterologist at Cleveland Clinic.

Acid reflux, which affects nearly a third of U.S. adults weekly, is the backward flow of stomach acid into the esophagus. Sometimes it progresses to a more serious condition called gastroesophageal reflux disease, or GERD.

Heartburn, on the other hand, is a symptom, not a condition. A burning pain in the chest can be caused by acid reflux or GERD. It can also be a sign of other problems, including heart trouble or a peptic ulcer, so it’s worth visiting a doctor if you have persistent heartburn, Dr. Lee said.

And if you think you have GERD, check in with your doctor to help you get it under control, Dr. Lee said, not only because you can get some relief, but because it has been associated with esophageal cancer .

Taking antacids regularly can cause (or mask) problems.

Just because antacids are often sold next to gum and mints at the drugstore doesn’t mean that you should eat them like candy, Dr. Balzora said. If you’re taking any antacids daily, or even a few times a week, that’s a sign that something could be wrong, she added.

Overusing these medications, she said, can cause additional problems. Regularly downing calcium-based antacids, for instance, can increase your risk for kidney stones.

You don’t have to poop every day.

Some people worry about not having a daily bowel movement, but constipation is generally defined as having fewer than three bowel movements a week .

“There’s a wide range of what’s considered normal,” Dr. Balzora said. If you’re a “three-a-weeker,” as she puts it, and you’re not having pain or difficulty passing or any other symptoms, she said, “then that’s fine.”

What’s more noteworthy is a sudden change in habits. If “you used to be a one-a-dayer and now you’re a once-a-weeker, or vice versa,” Dr. Balzora said, “then that needs to be evaluated.”

Constipated? Check your medicine cabinet.

If you have constipation, your first strategy should be to make lifestyle changes such as adding more water and fiber to your diet and exercising a little more, said Xavier Llor, a gastroenterologist at Yale Medicine.

But many people overlook how often medications can be a culprit, Dr. Llor said. “You’ll hear an ad with potential side effects, and get bored and stop listening, but so many medications are constipating,” he said.

Prescription medications like antidepressants and blood pressure medication can cause constipation, according to the National Institute on Aging. So can over-the-counter drugs like pain killers, antihistamines and some antacids , as well as calcium and iron supplements.

If you are using a medication that stops you up, “ask your doctor if there’s a nonconstipating alternative,” Dr. Llor said.

Healthy habits may lower your risk of I.B.S.

Irritable bowel syndrome, a gastrointestinal condition that brings on frequent episodes of diarrhea, constipation or cramping, is one of the most commonly diagnosed digestive disorders .

There’s no cure , but there are habits that may lower your overall risk of developing it, Dr. Balzora said. A recent study that followed almost 65,000 people for over 12 years looked at five healthy behaviors: never smoking, regular exercise, moderate alcohol consumption, a healthy diet and at least seven hours of sleep. Those who did at least three of those things had a 42 percent lower risk of developing I.B.S.

If you think you have I.B.S., don’t self-diagnose, said Natasha Chhabra, a gastroenterologist at Gastroenterology Associates of New Jersey. A doctor will perform specific tests, she said, as well as screen for conditions, like celiac disease.

As I wound up my chat with Dr. Balzora, she stressed the importance of having open conversations around bowel habits, and signed off with a possibly liberating fact: The average healthy person passes gas 10 to 20 times a day.

“I’m on a crusade to normalize flatulence, too,” she said.

Protect yourself from melanoma, a dangerous type of skin cancer.

About 100,000 people are diagnosed with melanoma each year in the United States. Ted Alcorn explores simple ways to reduce your risk and to catch possible cases early, while they are most curable.

Read the article: How to Avoid One of the Deadliest Forms of Skin Cancer

To get the best care at the dentist, speak up.

A visit to the dentist can be confusing or intimidating. Knvul Sheikh reports on how to demystify what’s going on in your mouth, and figure out what treatments are necessary.

Read the article: How to Advocate for Yourself at the Dentist

The Week in Well

Here are some stories you don’t want to miss:

Holly Burns finds that a little bit of dirt is good for you .

Amanda Loudin explores how to turn a bike ride into a bike workout .

Christina Caron reports on the growing practice of prescribing social activities for mental health.

Why do we have tick medication for dogs but not for people? Dana Smith investigates .

Let’s keep the conversation going. Follow Well on Instagram , or write to us at [email protected] . And check out last week’s newsletter about decluttering projects you can do in half an hour .

Jancee Dunn , who writes the weekly Well newsletter for The Times, has covered health and science for more than 20 years. More about Jancee Dunn

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Mental health and the pandemic: What U.S. surveys have found

The coronavirus pandemic has been associated with worsening mental health among people in the United States and around the world . In the U.S, the COVID-19 outbreak in early 2020 caused widespread lockdowns and disruptions in daily life while triggering a short but severe economic recession that resulted in widespread unemployment. Three years later, Americans have largely returned to normal activities, but challenges with mental health remain.

Here’s a look at what surveys by Pew Research Center and other organizations have found about Americans’ mental health during the pandemic. These findings reflect a snapshot in time, and it’s possible that attitudes and experiences may have changed since these surveys were fielded. It’s also important to note that concerns about mental health were common in the U.S. long before the arrival of COVID-19 .

Three years into the COVID-19 outbreak in the United States , Pew Research Center published this collection of survey findings about Americans’ challenges with mental health during the pandemic. All findings are previously published. Methodological information about each survey cited here, including the sample sizes and field dates, can be found by following the links in the text.

The research behind the first item in this analysis, examining Americans’ experiences with psychological distress, benefited from the advice and counsel of the COVID-19 and mental health measurement group at Johns Hopkins Bloomberg School of Public Health.

At least four-in-ten U.S. adults (41%) have experienced high levels of psychological distress at some point during the pandemic, according to four Pew Research Center surveys conducted between March 2020 and September 2022.

Young adults are especially likely to have faced high levels of psychological distress since the COVID-19 outbreak began: 58% of Americans ages 18 to 29 fall into this category, based on their answers in at least one of these four surveys.

Women are much more likely than men to have experienced high psychological distress (48% vs. 32%), as are people in lower-income households (53%) when compared with those in middle-income (38%) or upper-income (30%) households.

In addition, roughly two-thirds (66%) of adults who have a disability or health condition that prevents them from participating fully in work, school, housework or other activities have experienced a high level of distress during the pandemic.

The Center measured Americans’ psychological distress by asking them a series of five questions on subjects including loneliness, anxiety and trouble sleeping in the past week. The questions are not a clinical measure, nor a diagnostic tool. Instead, they describe people’s emotional experiences during the week before being surveyed.

While these questions did not ask specifically about the pandemic, a sixth question did, inquiring whether respondents had “had physical reactions, such as sweating, trouble breathing, nausea, or a pounding heart” when thinking about their experience with the coronavirus outbreak. In September 2022, the most recent time this question was asked, 14% of Americans said they’d experienced this at least some or a little of the time in the past seven days.

More than a third of high school students have reported mental health challenges during the pandemic. In a survey conducted by the Centers for Disease Control and Prevention from January to June 2021, 37% of students at public and private high schools said their mental health was not good most or all of the time during the pandemic. That included roughly half of girls (49%) and about a quarter of boys (24%).

In the same survey, an even larger share of high school students (44%) said that at some point during the previous 12 months, they had felt sad or hopeless almost every day for two or more weeks in a row – to the point where they had stopped doing some usual activities. Roughly six-in-ten high school girls (57%) said this, as did 31% of boys.

On both questions, high school students who identify as lesbian, gay, bisexual, other or questioning were far more likely than heterosexual students to report negative experiences related to their mental health.

Mental health tops the list of worries that U.S. parents express about their kids’ well-being, according to a fall 2022 Pew Research Center survey of parents with children younger than 18. In that survey, four-in-ten U.S. parents said they’re extremely or very worried about their children struggling with anxiety or depression. That was greater than the share of parents who expressed high levels of concern over seven other dangers asked about.

While the fall 2022 survey was fielded amid the coronavirus outbreak, it did not ask about parental worries in the specific context of the pandemic. It’s also important to note that parental concerns about their kids struggling with anxiety and depression were common long before the pandemic, too . (Due to changes in question wording, the results from the fall 2022 survey of parents are not directly comparable with those from an earlier Center survey of parents, conducted in 2015.)

Among parents of teenagers, roughly three-in-ten (28%) are extremely or very worried that their teen’s use of social media could lead to problems with anxiety or depression, according to a spring 2022 survey of parents with children ages 13 to 17 . Parents of teen girls were more likely than parents of teen boys to be extremely or very worried on this front (32% vs. 24%). And Hispanic parents (37%) were more likely than those who are Black or White (26% each) to express a great deal of concern about this. (There were not enough Asian American parents in the sample to analyze separately. This survey also did not ask about parental concerns specifically in the context of the pandemic.)

Looking back, many K-12 parents say the first year of the coronavirus pandemic had a negative effect on their children’s emotional health. In a fall 2022 survey of parents with K-12 children , 48% said the first year of the pandemic had a very or somewhat negative impact on their children’s emotional well-being, while 39% said it had neither a positive nor negative effect. A small share of parents (7%) said the first year of the pandemic had a very or somewhat positive effect in this regard.

White parents and those from upper-income households were especially likely to say the first year of the pandemic had a negative emotional impact on their K-12 children.

While around half of K-12 parents said the first year of the pandemic had a negative emotional impact on their kids, a larger share (61%) said it had a negative effect on their children’s education.

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How Americans View the Coronavirus, COVID-19 Vaccines Amid Declining Levels of Concern

Online religious services appeal to many americans, but going in person remains more popular, about a third of u.s. workers who can work from home now do so all the time, how the pandemic has affected attendance at u.s. religious services, economy remains the public’s top policy priority; covid-19 concerns decline again, most popular.

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7 Surprising Health Benefits of Matcha Tea

Research has found this ancient green powder may help memory and heart health, as well as promote healthy aging.

Angela Myers,

Once considered an exotic drink central to Japanese tea ceremonies, matcha is now found in coffee shops and cafes around the world. But matcha’s vibrant green hue isn’t just good fodder for Instagram feeds. This green powder may also boost the health of older Americans. Research has found benefits for memory, heart health , immune system and healthy aging.  

Many other types of teas and foods offer these benefits as well. Learn more about what sets matcha apart and whether it’s worth adding to your routine.

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What is matcha?

Known for its distinct green color, matcha is a highly concentrated, powdered form of green tea made from the Camellia sinensis plant. Tea leaves used for matcha are grown in shade, creating a richer, sweeter flavor than other teas.

“Matcha is most readily consumed as tea and people in Asia, especially in Japan and China, have drunk matcha tea for centuries,” says Frank Hu, the chair of the Department of Nutrition at Harvard T.H. Chan School of Public Health. Recently, matcha powders have also been added to smoothies, ice cream, desserts and infusions.

Benefits of matcha

Researchers believe matcha’s benefits primarily originate from the tea’s high concentration of polyphenols, an antioxidant-rich nutrient found in plants. Many other foods also contain polyphenols, but the concentration in matcha sets this powder apart.

“I expected matcha to have a high antioxidant potential, but the result surprised me,” Karolina Jakubczyk, a professor in the Department of Human Nutrition and Metabolomics at Pomeranian Medical University in Poland said in an email. “It is by far the strongest antioxidant I have tested in the lab.”

Jakubcyzk adds that the polyphenols are 10 times higher in matcha than in green tea.

Polyphenols are known for anti-inflammatory and antioxidant properties, says Ron Hills, a professor of pharmaceutical sciences who specializes in integrative nutrition at the University of New England. He says many of the potential health benefits of matcha likely come from polyphenols

1. May benefit brain health

Matcha is known for its properties that promote healthy aging, especially for brain health . Research published in 2020 study investigated the effect of matcha on older adults’ cognitive functioning in Japan. In the study, 61 participants received a daily drink with either matcha or a placebo for two weeks.

 Female participants who received matcha saw improvements for two markers of Alzheimer’s disease: overall functioning and episodic memory, the ability to remember details about everyday events. The male participants didn’t see the same results.

Other studies support matcha’s impact on memory, cognitive function and enhanced focus, though the research has found greater cognitive benefits in women than men and scientists say more large studies in humans need to be done to confirm matcha's benefits to brain health.

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2. Improves gut health

The polyphenols in matcha affect gut health .  Hills credits this to the EGCG catechins, a type of polyphenol highly concentrated in matcha.

The gut microbiome plays an important role in diseases like diabetes, obesity and liver disorders.

The EGCG catechins also add healthy bacteria to the gut and may improve metabolism. After two weeks of one matcha tea a day, changes often begin in the microbiome, Hills says.

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3. Lowers heart disease risks

Some research has found the antioxidant and anti-inflammatory properties in matcha may strengthen heart health.

A landmark study from 2001 found green tea, including matcha, prevented atherosclerosis, the buildup of plaques in the arteries, but the study was done in animals, not humans.

Recent studies on certain vitamins in matcha, including vitamin C , support the tea’s preventative properties against atherosclerosis, but more research is needed to confirm this effect.

4. Lowers stress

A 2023 analysis of studies in Current Research in Food Science found matcha may help decrease stress and anxiety . This may be due to matcha’s high levels of L-theanine, an amino acid linked to better mood and lower stress levels.

Swapping coffee or energy drinks for matcha may be a great way to get the benefits of caffeine without the stress because matcha’s caffeine properties differ from coffee.

“Coffee can cause rapid action, but also a sudden drop in energy and drowsiness, which is known as the ‘roller-coaster’ effect,” says Jakubczyk. “The caffeine in matcha has a different effect due to the presence of L-theanine, which makes the effects of matcha longer and milder.”

5. Supports a stronger immune system

A matcha a day keeps the doctor away. At least, that’s what evidence linking matcha to a stronger immune system suggests. Matcha’s anti-inflammatory properties support a healthy immune system, while its marked improvements in gut health also strengthen immune response.

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6. May slow premature aging

The catechins found in matcha help protect cells from oxidative stress, potentially slowing the aging process. This benefit was mainly found in the brain, but matcha may slow aging in other cells too.

7. May lower risk of certain cancers

One of the newest, and most exciting, possible benefits of matcha is its potential to lower cancer risk . Early studies on animals suggest it may interrupt cancer cells’ cycle regulation. Most of the studies look at matcha’s impact on breast cancer cells. Much more research on humans needs to be done, however, to prove these benefits. Studies on animals don’t always translate to human benefits.

“Overall evidence suggests potential for preventing cancer, but I don't think we have strong enough evidence to make recommendations for cancer prevention at this point,” Hu says.

Potential negative effects of matcha

Part of what makes matcha a superfood is its high concentration of micronutrients . However, Hu notes, it also has a higher concentration of caffeine than other teas, although it doesn’t have as much caffeine as coffee. 

Hu doesn’t recommend matcha for those who are sensitive to caffeine. Drinking too much matcha  — especially for those sensitive to caffeine —  can cause anxiety, higher blood pressure, difficulty sleeping and a faster heartbeat.

Jakubczyk’s team also found high concentrations of fluoride in matcha. Large amounts of fluoride have been linked to joint pain,brittle bones and diarrhea. However, significant amounts of fluoride must be consumed to experience these negative effects. One to two cups of matcha a day shouldn’t cause them.

Are some forms of matcha better than others?

“The important thing seems to be the introduction of matcha into the daily diet itself, the form is already secondary,” Jakubczyk says.

But not all forms of matcha are created equal. Adding sugar, cream or other processed ingredients won’t take away from matcha’s benefits, but it can negatively impact the body independent of matcha, Hu states. Matcha products without added sugars are better to consume than highly processed matcha desserts and beverages.

Ready to Try Matcha?

Here are some things to consider:

• The most common way to consume matcha is as a tea. Experts recommend purchasing ceremonial-grade matcha for maximum benefits.
• For a healthy take on a matcha latte, Hills suggests combining matcha, hot milk and honey.
• If lattes and tea aren’t for you, a matcha smoothie may do the trick. Hills adds almond milk, frozen spinach, frozen bananas, honey and matcha to his smoothie.
• Due to the high caffeine concentration, don’t consume matcha before bedtime, recommends Jakubczyk. Avoiding any caffeine four to six hours before bedtime is a good idea since that’s how long it takes to metabolize half of consumed caffeine.
• Some forms of matcha may be contaminated by pesticides or heavy metals, Hu says. To avoid contamination, purchase reputable, quality products.
• Matcha is an addition to a healthy diet, not a substitute. The health benefits from matcha may be more prevalent in individuals who eat a whole foods diet alongside matcha, suggests Hills.
• If already consuming coffee, be mindful when adding matcha to your diet. Matcha on top of two to three coffees a day may be too much caffeine, Hu says.

Angela Myers is a contributing writer who covers health and medical technology. Her work has appeared in  Forbes  and  Healthline , among other publications.

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New Research Suggests That Hugs, Even From A Robot, Really Help Alleviate Pain And Ease Feelings Of Depression And Anxiety

Most people enjoy the sensation of hugs, but now, a new study conducted by researchers in Germany has revealed that hugging really does positively impact both mental health and pain management.

Plus, the team found that even a short moment of contact – including one from a robot – can alleviate symptoms of pain and depression.

The researchers, who are from Bochum, Duisburg-Essen, and Amsterdam, analyzed more than 130 international studies – which involved around 10,000 individuals – to determine the impact of touch on human well-being.

Their findings clearly showed that touch can relieve pain, depression, and anxiety. Additionally, the study found that touch doesn’t need to be prolonged or even from another human in order to be effective. In fact, social robots, pillows, and weighted blankets were even found to improve well-being.

“We were aware of the importance of touch as a health intervention. But despite many studies, it remained unclear how to use it optimally, what effects can be expected specifically, and what the influencing factors are,” explained Dr. Julian Packheiser from Ruhr University Bochum.

When it comes to babies, the study indicated that they, too, benefit from hugs on a regular basis. However, they have to be given by the babies’ parents.

“In the case of infants, it’s important that it is the parents who administer the touch. Their touch is more effective than that of a care professional. In adults, however, we found there was no difference between people our volunteers were familiar with and a nursing professional,” detailed Dr. Helena Hartmann from the University of Duisburg-Essen.

Touching someone has the most significant effect on mental health, highlighting touch therapy as a valuable resource for those struggling with mental health issues. Furthermore, the researchers noted that touching can offer minor cardiovascular improvements, like better heart rate and blood pressure.

Perhaps more intriguingly, prolonged touch is not necessary to yield these benefits. Rather, research indicated that extended periods of tough – like 20-minute-long hugs – don’t enhance the positive effects on an individual’s well-being.

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• Research Highlight
• Published: 16 April 2024

Gut microbiota

Gut bacteria can break down cholesterol

• Irene Fernández-Ruiz 1  

Nature Reviews Cardiology ( 2024 ) Cite this article

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Alterations in the gut microbiome have been associated with an increased risk of cardiovascular disease (CVD), but the underlying mechanisms are not fully understood. A study published in Cell now identifies a group of gut bacteria that can metabolize cholesterol and are associated with lower plasma cholesterol levels. Thus, these gut bacteria could have potential benefits for lipid homeostasis and cardiovascular health.

Next, the investigators showed that Oscillibacter can metabolize cholesterol through multiple pathways. Molecular networking and structural similarity searches using a protein language model identified several candidate genes involved in cholesterol metabolism in Oscillibacter . Functional prediction and in vitro assays of multiple gut Oscillibacter isolates from human samples demonstrated that Oscillibacter have conserved cholesterol-metabolizing capacity, with efficient cholesterol uptake and transformation into cholestenone, glycosylated cholesterol and hydroxycholesterol.

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Original article

Li, C. et al. Gut microbiome and metabolome profiling in Framingham Heart Study reveals cholesterol-metabolizing bacteria. Cell 187 , 1834–1852.e19 (2024)

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Chakaroun, R. M. et al. The potential of tailoring the gut microbiome to prevent and treat cardiometabolic disease. Nat. Rev. Cardiol. 20 , 217–235 (2023)

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Fernández-Ruiz, I. Gut bacteria can break down cholesterol. Nat Rev Cardiol (2024). https://doi.org/10.1038/s41569-024-01026-w

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