Written by Ambika Nair

“You are what you eat”, but how about when it comes to your mental health: is your mental health truly an impression of ‘what you eat’? 

For a while now, we have correlated healthier eating to a more positive and overall improved mental health. However, only very recently have we begun to understand the science behind this phenomenon known as ‘nutritional psychiatry’, where nutritional interventions are studied for the treatment of mental health issues. In 2020, a team of scientists in the Harvard Review of Psychiatry wrote that:

“a growing body of literature shows that the gut microbiome plays a shaping role in a variety of psychiatric disorders including major depressive disorder metabolites that are produced from gut microbes”. 

The impact of the gut microbiome on our mental health is becoming increasingly important especially in addressing the mental health of food insecure populations in the U.S.

The Science Behind the Microbiome

Our guts contain trillions of microbes which make up the so-called gut microbiota. These microbes are responsible for maintaining homeostasis via aiding in absorbing nutrients, digestion, immunity and anti-inflammation, as well as playing a vital role in endocrine signaling to the brain. The brain-gut-microbiome (BGM) axis is a newly unearthed connectivity of bidirectional systems between the brain and gut microbiome. Dietary consumption of complex carbohydrates and amino acids in a variety of foods are taken up by microbes residing in the gut. These microbes then transform these carbs and amino acids into molecules and metabolites such as short-chain fatty acids and tryptophan, which then interact with entero-endocrine cells (EEC) in the GI endocrine tract. This interaction enables EECs to act as neurotransmitter signaling molecules either locally or to the Central Nervous System. 

One example of this signaling pathway includes dietary tryptophan. Tryptophan is the sole precursor amino acid to the production of serotonin: the ‘happiness’ hormone. Diets with high levels of this amino acid include cheese, egg whites, chicken, fish, milk, and turkey. When ingested, the amino acid is transformed by gut microbes into further metabolites which are later released into the bloodstream and act as signalers on the Central Nervous System. The release of these metabolites triggers the release of serotonin via EECs. According to the American Psychological Association, ninety-five percent of our bodies’ serotonin is produced via the gut microbiome, and this production is due to the consumption of foods known to be “typically healthy.”

Additionally, the gut microbiome interacts with inflammatory systems through a gut microbiome- immune system – brain axis bidirectional pathway found to be highly involved in stress-related mental issues including major depressive disorder and anxiety. In a recently published paper, the Czech Academy of Sciences highlights how during times of stress, the epithelial layers of the gut tend to become much more permeable to excretion of endotoxins – bad gut bacteria – which consequently leads to chronic inflammation that is present in individuals suffering from depression and anxiety. 

We’ve heard that increased levels of refined sugars not only have detrimental effects on physical health but also increase symptoms of depression and anxiety. Why is this the case? Sure enough, the gut microbiome – immune system – brain axis gives us an explanation. High-sugar diets lead to higher gut permeability of bad gut bacteria, which contributes to chronic systemic inflammation and consequently increased stress and depressive levels. Preclinical studies have recently found that an increase in probiotics in our diets, however, helps to reduce this permeability of the gut and may be a key dietary intake to improving stress-related mental health issues. The term “psychobiotics” is now being used to describe probiotics that influence our mental health. 

Grasping an understanding of the roles of microbial endocrine signaling and anti-inflammatory responses that the gut microbiota contributes, it is evident how certain diets and foods we put in our bodies are imperative to shape mental wellbeing. What do we mean when we say “typically healthy” foods? Foods high in tryptophan to boost serotonin levels via the gut-brain-microbiome axis include salmon, nuts and seeds, tofu, turkey, eggs, and cheese. However, it is also important to understand how these foods are processed, which affects the inflammatory response of the gut. On that note, Omega-3 fatty acids contain anti-inflammatory responses in the gut, and are considered beneficial as opposed to Omega-6 fatty acids, especially for individuals battling depression and anxiety. However, the typical American diet contains far more Omega-6 fatty acids as opposed to Omega-3. Foods with Omega-6 tend to be highly refined and processed. On the other hand, traditional Japanese and Mediterranean diets with higher dietary intakes of seafood, vegetables, fruits, healthy carbohydrates, and healthy fats may be linked to a reduction of depression by a third of that of the US. Especially non-western preparation of fruits and vegetables which tend to be fermented more often, also provide probiotics, or psychobiotics, needed to aid in anti-inflammatory responses in the gut, and improve mental health.  

Low income and Food Insecurity

The gut microbiome plays a major role in a variety of bidirectional pathways on the Central Nervous System, many of which are still not fully understood. Realizing how the food we eat biologically impacts our mental health is necessary to understanding this process on a socioeconomic scale. In many under-privileged populations in America, individuals experience geographical, educational, and economical marginalization from food security, and are barred from access to crucial and typically ‘healthy’ foods required for improved effects on mental health through the gut microbiome – brain axis. Food insecurity disproportionately affects low-income communities: during the COVID-19 pandemic, forty-four percent of low-income households in the US experienced a degree of food insecurity. Living in food-desert areas that were blocked from metropolitan cities due to closure of public transport, many low-income families found themselves not able to reach adequate, nutritious, and affordable food supplies. Additionally, with the closure of school systems during the pandemic, children of low-income families who relied on their school systems’ food supplies were also cut off from their few avenues of access to adequate, healthy food. With less-nutritious foods being much more economically sustainable for low-income populations, this benefit rationally outways the nutritional cost of consuming high caloric and low nutritional quality foods. Furthermore, education on the impact of foods with high nutritional quality is especially inadequate in low-income populations.

Food insecurity and Mental Health

Through economical, geographical, and educational factors, the influence of poor diet on low-income communities becomes a lot more clearer. This nutritional influence translates over to the gut microbiota’s influence of nutrition on mental health especially in underserved populations. When we think about our current nutritional crisis in underserved populations in the US, our minds naturally tend to link poor nutrition with increasing obesity rates and higher risks of CVD, Type 2 Diabetes, and osteoporosis. While this statistic is true, with food-insecure adults having a thirty-two percent higher risk of obesity than food-secure adults in the US, it is equally important to understand the link between food insecure populations and mental wellbeing. Mental health issues are exacerbated in low-income communities and may be contributed to a number of factors including poverty, violence, crime, parenting styles, childhood development, social status stigma, etc, keeping individuals unable to break out of the cycle of the population’s needs. However, nutrition too is a powerful factor to consider. A survey conducted by the Department of Agriculture at the University of Arkansas found there to be a high correlation between food insecurity and anxiety and depression during the COVID-19 pandemic which was three times more prevalent than mental-health related disorders associated with losing jobs during the pandemic. As an article from the Public Health Nutrition highlights, there is a bidirectional relationship between food insecurity, nutrition, and depression; experiencing food insecurity is correlated with high depression and similarly, depression may contribute to increased food insecurity. A major symptom of depressive mood disorders is a lack of motivation for simple tasks. When there is a lack of motivation to buy and prepare nutritious foods specifically geared towards maintaining a healthy gut microbiota, this negatively affects the individual’s biochemical makeup in the gut, resulting in even poorer mental health states. This cycle continues especially in low-socioeconomic communities, and while it is not necessarily in a person’s ability to magically change their current mental or socio-economical state, it is important that individuals in food-insecure populations receive adequate, nutritious foods and education on the importance that these foods have on our biological systems. These actions are with the hope that especially underserved communities will at the very least be able to change and control the contents that they consume.  

With the United States already topping the charts having some of the highest levels of mental health-related illnesses and disorders among high-income countries, it is especially important to look at this statistic in correlation to dietary intakes in food insecure populations. In 2016, twenty-six percent of adults in the US reported a mental health diagnosis such as anxiety and depression, and many more live undiagnosed. In terms of food insecurity, over thirty-three million Americans live in food insecure populations, and struggle with access to affordable and nutritious dietary intakes. Especially in rural areas of the US, families experience higher rates of food insecurity of 10.8% compared to 10.1% in metropolitan areas. A majority of our food insecurity crisis revolves around the nutritional content of our foods over actual amounts of food consumed – food insecurity rather than food insufficiency. In 2019, the USDA estimated that 10.5 percent of Americans were food insecure, compared to 3.7 percent of Americans who were considered food insufficient. The contents of the foods we typically consume in America with higher processing and refining levels is counter to recent findings on foods required to consume for a healthy gut microbiome, and consequently a healthy mental state and physical state of mind. The intersectionality of our specific food insecurity crisis and so-called ‘western’ diet makes low-income populations in the United States especially vulnerable to mental health crises. 

How can we fix this?

The next step is to ask, how can we go about fixing this disparity in mental health and food insecure populations in the United States? Currently, a variety of programs including The Supplemental Nutrition Assistance Program Education (SNAP-ED) and the National School Lunch Program (NSLP) are working to deliver nutritious foods and food education to food-insecure populations. SNAP-ED is an extension program of SNAP, which focuses on educating families and individuals in the SNAP program on how to economically shop for and cook nutritious foods, as well as conducting a variety of nutrition education programs. Recent nutritional education articles pertaining to the gut microbiome are in-fact funded by SNAP-ED, which is becoming increasingly important with the ongoing research about the role of our gut-microbiome on mental health.(source?) Since 2012, other non-profit organizations have emerged to not only provide nutritious food, but nutrition education. One of these organizations is called ‘Brighter Bites’ – a nonprofit that works to implement both nutrition education and fresh fruits and vegetables to families in need. This duality of nutritional food service and education is indispensable to improving dietary behavior in America, and consequently, improving mental health states especially in underserved areas.

The NSLP is a federally-assisted meal program that’s goal is to deliver nutritious, low-cost and free meals to public school children. The NSLP is required to provide children with adequate nutritional needs – one-third of daily caloric intake during lunch meals encompassing protein, calcium, iron, vitamin A and E. Backpack food drives have become especially popular since the COVID-19 pandemic hit – volunteers work to organize bags of nutritious meals for children in organizations such as “One More Child” and “KidsPack.” 

It is especially important to consider that families with children in low-income households tend to be much more susceptible to food-insecurity, having to feed more individuals. Hence, children growing up in food insecure households are more likely to grow up not understanding the importance of nutrition on their wellbeing both mentally and physically. With recent findings on the gut microbiota – brain systems, the importance of what we put in our bodies is slowly growing its prevalence in the U.S. There is much more on the functionality of this gut-to-brain system that scientists are currently researching, and the summation of effects that the nutritional content in our gut may have on our mental healths may be an infinite amount of possibilities. From a biological standpoint, it is fundamental that we continue to educate ourselves on these bodily systems and especially individuals in low-income populations.

Diagram by the Microbiome Research Reports on the impact of Gut Microbiota on maintaining homeostasis in the brain