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Mental Health and Nutrition Connection

Society in the United States has made huge strides in the last few years opening up the discussion of mental health issues, and although there is a long way to go, the acceptance and ability to share struggles and treatment options is critical. In the US, anxiety is the leading mental illness affecting 40 million adults 18 and older. Depression is the leading cause of disability in the US between people ages 15 to 44, and affects 17.8 million adults (“Understand the FACTS: Anxiety and Depression Association of America, ADAA.”). These numbers are astonishing, but represent a strong case for the movement into vaster ways to manage these silent disorders. Anxiety can result from a variety of life experiences including trauma, stress, drugs and alcohol as well chemical imbalances in the brain, personality type and genetics (“Anxiety Disorders”). Depression is also a result of chemical imbalances in the brain, as well as genetics, early childhood trauma, brain structure, medical conditions, drug and alcohol use, stress and low self esteem (Higuera). Current anxiety and depression treatments include those from professionals such as psychiatrists who prescribe medications, most commonly antidepressants, SSRI’s (selective serotonin reuptake inhibitors) and SNRI’s (selective serotonin and norepinephrine inhibitors), and psychologists who provide various types of therapy, and recommendations for meditation and breathwork. Many lifestyle habits have been used to manage anxiety and depression as well such as exercise and adequate sleep (Higuera).

While diet is not commonly listed as an anxiety and depression cause or treatment, nutritional psychiatry is a new term referring to the use of nutrition as a tool for mental health (Selhub). It seems logical, as filling your body with quality, nutritious foods would help it run at it’s best. Recent studies have made great progress into how our brain and gut are related, and the relationship of our gut health to anxiety and depression. The gut microbiome, gut-brain axis, as well as specific diets and vitamins may play a bigger role in anxiety and depression than you may think, and may even lead to some alternative options for managing symptoms.

Understanding the gut microbiome is an important first step in understanding its connection to anxiety and depression. Our GI tract, or gut, is filled with trillions of bacteria that are essential for health.These bacteria are most commonly found in the intestines, and contain more microbiota than total cells in our body. There are more than 1,000 species, with the main phyla consisting of bacteroides, firmicutes and actinobacteria (Cresci and Izzo). Our gut microbiome is involved in important tasks like nutrient absorption, synthesis of enzymes, vitamins and amino acids and when in balance a protection from chronic health conditions like diabetes and obesity. The gut microbiota can be influenced by many factors, like diet, stress, genetics and use of antibiotics (Cresci and Izzo). Eating prebiotic foods stimulates the growth of beneficial bacteria and eating probiotic rich foods, which contain live bacteria, increases the amount of beneficial bacteria in your gut. While there is no definition of a “normal gut microbiome” as it varies from person to person, dysbiosis, which is an imbalance in the gut microbiome can cause many issues (Clapp). Now that we know what our gut microbiome is, let’s explore the gut-brain axis.

The gut-brain axis (GBA) is a “bidirectional communication system between the central nervous system and the GI tract”. (Vissavajjhala). The gut and brain send and receive messages through multiple pathways including the enteric nervous system, neural pathways, the vagal nerve, which directly connects the digestive system to the brain, and through the bloodstream. Because of this connection the gut and its microbiota can have effects on endocrine function, the nervous system and behavior regulation (Schnorr and Bachner). On top of that, the GI tract is lined with tons of nerve cells that help you digest but also guide your emotions. Serotonin, a neurotransmitter that regulates sleep, appetite, and mediates mood and inhibits pain, is largely produced in the GI tract. Serotonin reduces depression and regulates anxiety (Selhub). The production of these neurons and neurotransmitters is greatly affected by the good bacteria in your microbiome. The gut microbiome can also have an effect on anxiety and depression through inflammation. When our GI tract becomes inflamed cytokines and neurotransmitters are released and intestinal permeability is increased, which allows these molecules to travel throughout the body (Clapp). These molecules can then increase the permeability of the blood brain barrier, and when released into the brain can affect brain function, including anxiety and depression (Clapp).

Most of the research done on the gut-brain axis and anxiety and depression is done in animals, while many human studies are still in the works. In one study, mice were treated with either probiotics, antibiotics or pathogenic bacteria, and all of their behavior was changed, indicating a change in microbiota changes behavior (Foster and Neufeld). In another study mice were given the probiotic L. Rhamnosus, and had decreased anxiety and depressive behavior, and when given a pathogenic infection C. Jejuni, anxiety behaviors increased (Foster and Neufeld). As mentioned, the work on humans is limited but there is some evidence to suggest how the makeup of the gut microbiome and its connection to our brain has an effect on anxiety and depression. In a double blind, placebo controlled trial, healthy subjects were given a probiotic drink while others received a placebo for 3 weeks. Their mood and cognition was assessed before the trial and after. Subjects who scored low for depressed mood in the beginning showed great improvements in overall mood after having the probiotic drink (Foster and Neufeld). In another human double blind, placebo controlled study, participants were given a mixture of probiotics while the other received a placebo. A questionnaire was given to test anxiety, depression and stress, and the group who had the probiotics showed less psychological distress than the placebo group (Foster and Neufeld). These studies suggest that probiotics, which have a positive effect on the makeup of the gut microbiota, also have an effect on mood and our behavior.

Another connection between anxiety and depression and our gut is through the hypo-thalamic-pituitary axis (HPA). The HPA is a neuroendocrine mechanism that is activated when we are exposed to stress, as it helps to regulate specific body functions during this time (Neurosci). To explain it simply, when we feel stressed, the hypothalamus and pituitary gland release specific hormones into our bloodstream to help us manage the stress. One hormone produced by these secretions is cortisol, which has a number of ways of helping your body manage stress, like increasing blood pressure and cardiac output and increasing glucose levels in your cells for energy (Neurosci). When HPA is regulated properly it’s highly functional and important but issues arise when it becomes dysregulated or hyperactive. When this occurs, like when someone faces high stress levels daily, psychiatric distress can occur like anxiety and depression. Even early life trauma can cause a hyperactive HPA axis later in life, contributing to anxiety (Neurosci). The HPA axis is an important factor in anxiety and depression, and is also connected to our gut microbiome and the gut-brain axis.

Firstly, we know our gut microbiome is sensitive to stress, and therefore can be put into dysbiosis because of it. Probiotics, specifically lactobacillus and bifidobacterium have been found to reduce stress induced HPA axis dysfunction and improve anxiety and depression symptoms. In one study done, hyperactivity of the HPA axis in mice was reversed by the consumption of bifidobacterium probiotics and in another done on rats, probiotic use reduced HPA axis response to psychological stress (Misiak). This connection can be explained by a few theories. One is that our gut microbiota being altered and increasing intestinal permeability can release pro-inflammatory cytokines and microbial antigens among others that activate the HPA axis, and therefore cause hyperactivity (Misiak). While this is a growing area of study, it's clear there is a link between our gut and the HPA axis and their involvement in depression and anxiety.

Looking deeper into the gut’s connection to anxiety and depression, specific disorders, including major depressive disorder and generalized anxiety disorder have been assessed. In major depressive disorder, studies done to examine the makeup of the gut microbiota of patients with major depression was done, and 9 genera had higher amounts, while 6 particular genera, including bifidobacterium were lower (Misiak). This shows a commonality in the microbiomes of major depression patients. Clinical studies done also reported that probiotics only, not prebiotics, exerted small antidepressant and anxiolytic (anti-anxiety) effects (Misiak). In generalized anxiety order, similar studies were done, but the makeup of the patients microbiome was compared with healthy individuals. The studies showed patients with generalized anxiety disorder had less diversity of microbiota than healthy patients, but the variety did not increase once patients were in remission, and dysbiosis continued. This implies that the less varied gut microbiota, the more likely a person is susceptible to disease (Misiak).

In terms of a diet best for depression and anxiety, there is unfortunately no specific way of eating to prevent or manage anxiety and depression. There are some hopeful correlations that can be worth exploring though, and overall eating a more healthy, balanced diet may increase your energy levels, self-esteem and ability to think clearly. Our brain depends on nutrients like lipids, amino acids, vitamins and minerals that we get from our diet to function, and gut hormones, neuropeptides and the gut microbiota are all affected by what we eat as well (Adan). This means the food we put in our body can have an impact on the way we feel and how our gut communicates with the brain. Diets high in fresh fruit and fresh vegetables have been linked to higher levels of happiness (Adan). The Mediterranean diet, composed largely of fresh fruit, veggies, whole grains, legumes, fish, olive oil and poultry, eaten over a 12 week period was linked to improvements in mood and reduced anxiety in adults with major depressive disorder (Adan). Both these diets overwhelmingly show the importance of a balanced diet filled with whole foods.

Turning to things that can negatively affect your cognition and therefore anxiety and depression are some vitamin deficiencies. Vitamin B12 deficiency can cause lethargy, poor memory and depression, while folic acid deficiency has been linked to a greater risk of adult depression (Adan). To ensure you are not deficient in any of these vitamins, talk to your doctor. Foods high in vitamin B12 are beef, clams and fortified cereals and foods high in folic acid are legumes, leafy greens and citrus fruits. Supplementation can also be used to achieve adequate levels of each if getting them though the diet is challenging. Alcohol is one beverage that's linked to increased anxiety. “Hangxiety” is a common term to describe the increased feelings of anxiety the morning after drinking. When we drink, dopamine fills our brain and we feel a sense of calm, but when that wears off, withdrawal effects happen and anxiety increases. Paired with lack of sleep, fogginess, and reduced cognition, it’s a recipe for anxiety. Long term use of alcohol can also cause or worsen anxiety (“Hangxiety: The Link Between Anxiety and Alcohol”).

So, having a healthy gut seems to be an important factor in maintaining overall health, as well as mental health. But how can we know if our anxiety and depression is a result of our gut microbiome? Unfortunately, there is no way to really tell, but you can do things to make sure your gut is as healthy as possible. These include things like consuming prebiotic and probiotic foods or supplements. Examples of prebiotic foods include but are not limited to: onions, asparagus, bananas and garlic. Probiotic foods include fermented foods like yogurt, kombucha drinks, buttermilk and kimchi. Eating a varied diet with lots of fruit and vegetables and fiber, and less artificial sugar and processed foods is also beneficial for the microbiome (Cresci and Izzo). Prebiotic and probiotics can also be taken through supplements that can be bought at most pharmacies and food stores. Lastly, we saw how much of an effect stress has on our body’s processes. Reducing stress can help to reduce risks of dysbiosis in your gut and can be done in many ways. While relieving stress is personal, things like exercise, meditation, talking to a therapist, breathwork, among many others can help reduce day to day stress.

Bottom Line:

The link between our gut, diet and anxiety and depression is one you may have not thought about before, but the science is pointing towards some interesting conclusions. Treating your body with care and keeping your gut healthy with nutritious foods may not be a miracle worker for your mental health, but it can be a great place to start. A healthy diet will keep your body healthy, full of energy and able to function at its best. Diet is not a replacement for other anxiety and depression treatments, like medications or therapy, but who knows, it may help you think a bit clearer and change the way you feel.

Written by Carley Higgins on behalf of Supriya Lal


Adan, Roger A.H., et al. “Nutritional Psychiatry: Towards Improving Mental Health by What You Eat.” European Neuropsychopharmacology, vol. 29, no. 12, 2019, pp. 1321–1332., doi:10.1016/j.euroneuro.2019.10.011.

“Anxiety Disorders.” Mayo Clinic, Mayo Foundation for Medical Education and Research, 4 May 2018,

Clapp, Megan, et al. “Gut Microbiota’s Effect on Mental Health: The Gut-Brain Axis.” Clinics and Practice, vol. 7, no. 4, 2017, pp. 131–136., doi:10.4081/cp.2017.987.

Cresci, Gail A.M., and Kristin Izzo. “Gut Microbiome.” Adult Short Bowel Syndrome, 2019, pp. 45–54., doi:10.1016/b978-0-12-814330-8.00004-4.

Foster, Jane A., and Karen-Anne McVey Neufeld. “Gut–Brain Axis: How the Microbiome Influences Anxiety and Depression.” Trends in Neurosciences, vol. 36, no. 5, 2013, pp. 305–312., doi:10.1016/j.tins.2013.01.005.

“Hangxiety: The Link between Anxiety and Alcohol.” Henry Ford LiveWell,

Higuera, Valencia. “Everything You Want to Know about Depression.” Healthline, Healthline Media, 11 Feb. 2020,

Misiak, Błażej, et al. “The Hpa Axis Dysregulation in Severe Mental Illness: Can We Shift the Blame to Gut Microbiota?” Progress in Neuro-Psychopharmacology and Biological Psychiatry, vol. 102, 2020, doi:10.1016/j.pnpbp.2020.109951.

Neurosci. “Know Your Brain: Hpa Axis.” Neuroscientifically Challenged, Neuroscientifically Challenged, 4 Jan. 2021,

Schnorr, Stephanie, and Harriet Bachner. “Integrative Therapies in Anxiety Treatment with Special Emphasis on the Gut Microbiome.” Yale J Bio Med, vol. 89, no. 3, 30 Sept. 2016.

Selhub, Eva. “Nutritional Psychiatry: Your Brain on Food.” Harvard Health, 26 Mar. 2020,

“Understand the FACTS: Anxiety and Depression Association of America, ADAA.” Anxiety Disorders and Depression Research & Treatment,

Vissavajjhala, Prabhakar. “Impact of Nutrition on Healthy Aging.” Nutrition and Functional Foods for Healthy Aging, 2017, pp. 3–10., doi:10.1016/b978-0-12-805376-8.00001-0.

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