How Food Exerts Its Effects on Our Mental Health

Written by Nicole Lippman-Barile, Ph.D., N.T.P.

Mental Health, Food, and the Gut-Brain Axis

Mental health encompasses our psychological, emotional, and social well-being. It involves our thoughts, behaviors, and emotions, and it also affects the state of our physical health. One of the most modifiable ways you can positively affect your mental health is with food. There are many reasons why food affects our mental health, and one of the reasons is the way it interacts and affects our gut and the gut-brain axis. The gut-brain axis is a bidirectional communication network between our brain (the central nervous system) and our gut (the enteric nervous system). In this article, we’ll highlight the ways in which we currently understand how food can affect our mental health through:

  • Gut microbiota
  • Fiber and probiotics
  • Inflammation and anti-inflammatory diets; and
  • BDNF (brain-derived neurotrophic factor)

Our Gut Microbiota

Within our guts reside a complex and dynamic population of millions of bacterial micro-organisms. These micro-organisms are collectively referred to as the gut microbiota, and they exert significant influence on our mental health, immune health, cardiovascular health, hormonal health, metabolism, body weight, and even some aspects of our behavior. The kinds and types of gut bacteria that live in our guts are influenced by a number of different factors. The most direct influence across our lifetime is our diet.1 In fact, your diet is responsible for more than 60% of the bacterial variation in the gut.

Mental health can be affected when there is an alteration or imbalance in the gut microbiota, known as dysbiosis. This can occur due to illnesses, certain diets, or the prolonged use of antibiotics. A dysbiotic state can lead to increased intestinal permeability, allowing substances like bacterial metabolites from the gut to cross directly into our blood circulation, an occurrence known now as “leaky gut.” This can create further inflammation in the body as these inflammatory metabolites are circulated, eventually contributing to inflammation in the brain, called “neuroinflammation.” Increased intestinal permeability can lead to negative effects, such as inflammatory bowel disease and psychiatric disorders, including depression and anxiety.2

How Fiber Nourishes Our Microbiota

Fiber is the preferred food for our gut microbiota, as they are able to ferment certain fiber and then produce short chain fatty acids (SCFA) as by-products. The SCFA’s are powerful agents that help to decrease inflammation. This is one of the major ways in which our gut microbiota help to promote our mental well-being. Foods that help to support the production of SCFA’s via fermentation are indigestible carbohydrates, including resistant starches, inulin, and fructooligosaccharides. These are known as “prebiotic” foods that promote the growth of these beneficial gut microbes. Prebiotic foods include garlic, onions, asparagus, leeks, and bananas. Also, incorporating whole grain products and vegetables will help to populate the kinds of microbiota that will benefit our mental health, as well as including probiotic foods. “Probiotic” (as opposed to prebiotic) foods contain live bacteria that when consumed, will populate and colonize within our guts. Probiotic foods include fermented foods like sauerkraut, kimchi, yogurt, cheese, as well as miso, kefir, and sourdough bread.

Inflammation and Mental Health

Research has now demonstrated that inflammation plays a central role in the pathogenesis of depression and other mental health conditions, including anxiety disorders and schizophrenia. Several studies demonstrate that depression is associated with elevated levels of a number of biomarkers that indicate inflammation, including C-reactive protein (CRP) and IL-6.3 These inflammatory substances are able to access the brain and contribute to the pathophysiology of depression, including the disruption of neurotransmitter metabolism and endocrine function. This activation of inflammation is believed to contribute to oxidative stress, which creates further neuroinflammation.

The causes of inflammation include unmanaged autoimmune disease, high blood sugar, excess alcohol consumption, inflammatory diets and foods, as well as leaky gut and bacterial infections. One powerful way to help manage inflammation both in your brain and body is with your diet. Data from a variety of population-based studies demonstrate an association between habitual dietary patterns and levels of inflammation in the body. For example, in the Nurses’ Health Study, a healthy (‘prudent’) dietary pattern, characterized by higher intakes of vegetables and fruit, whole grains, fish and legumes, was associated with reduced plasma concentrations of inflammatory markers, including CRP and IL-6; while an unhealthy (‘Western’) pattern, high in red and processed meats, refined carbohydrate and other processed foods, was associated with increased inflammatory markers. Interestingly, specific compounds in whole foods influence levels of inflammation. For example, beta glucans, found abundantly in whole grains, help to improve the health of our immune system. Whole grain foods are also high in phytochemicals, compounds found in plants, which protect against the oxidative stress that is a consequence of inflammation.

The Mediterranean diet, as well as many other healthy dietary patterns like the MIND diet, help to lower levels of inflammation in the body.  On the other hand, diets consisting of processed foods and refined carbohydrates (like white breads, white rice, and processed cereals) are associated with higher levels of inflammation. In addition, diets higher in omega-6 fatty acids (from refined seeds and vegetable oils, like canola oil), increase the production of pro-inflammatory cytokines. Incorporating fresh fruits and vegetables, seafood, whole grains, and olive oil help to significantly reduce inflammation and neuroinflammation, helping to benefit our overall mental health. (It’s also worthy to note that while inflammation can be caused by poor diet, psychosocial stress is also capable of stimulating inflammatory signaling molecules by activating the sympathetic nervous system.3 Psychosocial stress is stress that can arise from our social interactions with others, including real or imagined threats to our social status, respect, and/or self-worth. Such stress is a well-known precipitant of mood disorders.)

Brain-Derived Neurotrophic Factor (BDNF) and Mental Health

BDNF is a neurotrophin molecule that is heavily involved in cognition. In both humans and animals, high levels of BDNF are found in multiple brain regions, including the hippocampus, amygdala, cerebellum and cerebral cortex, with the highest levels found in the hippocampus, a structure responsible for learning and memory. BDNF is also involved in neurogenesis (the birth and growth new neurons) and helps to protect existing cells from oxidative stress. Lower levels of BDNF are seen in individuals with clinical depression, bipolar disorder, and schizophrenia.4 There is also evidence that those with these mental health disorders have smaller hippocampi. Increasing levels of BDNF can help to increase the size of the hippocampus over time, and your diet is a major contributor in helping achieve this. In fact, a diet lacking in nutrient-dense foods is associated with smaller left hippocampus volume.

BDNF is increased by consuming foods high in polyphenols. Polyphenols are plant compounds that have antioxidant and anti-inflammatory properties. Foods rich in polyphenols include colorful fruits, vegetables, teas, spices, and wine.5 Specifically, olive oil, green tea, and coffee have been shown to increase levels of BDNF in certain brain regions after consumption.6 In addition to your diet, exercise also has the ability to increase levels of BDNF, giving us at least two ways to boost it.

Eat to Improve Mental Health!

Mental health is complex, and using food as a way to improve it is both accessible and effective as long as you understand the basics. Try incorporating the foods we mentioned to help improve your overall mental health!


Written by Nicole Lippman-Barile, Ph.D., N.T.P.

Dr. Lippman-Barile is a licensed Clinical Psychologist and a Nutritional Therapy Practitioner (NTP) who practices in New York. As a psychologist, Dr. Lippman-Barile specializes in treating anxiety and mood disorders, and she is an expert in treating Obsessive Compulsive Disorder (OCD) and related compulsive disorders. As a nutritional therapist, she specializes in treating blood sugar dysregulation, digestive health, and helping to improve mood using food and lifestyle modifications. Dr. Lippman-Barile intimately cares about the connection between gut health and brain health, and she applies evidence-based research in this field to optimize physical, mental, and emotional status. Dr. Lippman-Barile believes that by understanding the science behind the reasons for selecting and eating certain foods, as well as engaging in certain lifestyle behaviors, we can achieve more sustainable, effective, and longer lasting health.  Dr. Lippman-Barile holds a Ph.D. in Clinical Psychology from Hofstra University and a Nutritional Therapy Practitioner Certification.  On the internet, she can be found at Feed Your Mental (www.feedyourmental.com).


References

  1. Thursby, E., & Juge, N. (2017). Introduction to the human gut microbiota. The Biochemical journal474(11), 1823–1836. https://doi.org/10.1042/BCJ20160510
  2. Carabotti, M., Scirocco, A., Maselli, M. A., & Severi, C. (2015). The gut-brain axis: interactions between enteric microbiota, central and enteric nervous systems. Annals of gastroenterology28(2), 203–209.
  3. Miller AH, Maletic V, Raison CL. Inflammation and its discontents: the role of cytokines in the pathophysiology of major depression. Biol Psychiatry. 2009;65:732–741
  4. Lin, C. C., & Huang, T. L. (2020). Brain-derived neurotrophic factor and mental disorders. Biomedical journal43(2), 134–142. https://doi.org/10.1016/j.bj.2020.01.001
  5. Gomez-Pinilla, F., & Nguyen, T. T. (2012). Natural mood foods: the actions of polyphenols against psychiatric and cognitive disorders. Nutritional neuroscience15(3), 127–133. https://doi.org/10.1179/1476830511Y.0000000035
  6. Sangiovanni, E., Brivio, P., Dell'Agli, M., & Calabrese, F. (2017). Botanicals as Modulators of Neuroplasticity: Focus on BDNF. Neural plasticity2017, 5965371. https://doi.org/10.1155/2017/5965371
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