The Gut and Brain Connection

We’ve long known that when we experience strong emotions like anxiety or grief, we feel it in our gut. Before a presentation, we might have ‘butterflies in our stomach’. Or when we see something that shocks or upsets us, we often describe the experience as ‘gut-wrenching’. Our bodies have a physical reaction to our emotional state.


But our gut health also directly impacts our mental health. Today, there’s a wealth of research demonstrating the gut and brain are closely interconnected. And that has big implications for how we manage our mental wellbeing during recovery.


The Second Brain


Our gut has its own network for autonomous regulation known as the ‘enteric nervous system’, which is made up of hundreds of millions of nerve cells that help manage digestion. This has been called our ‘second brain’ because its vast circuitry of neurons allow it to operate independently from and communicate with our brain and spinal cord.


In fact, our gut generates and responds to many of the same chemicals that our brains use to regulate mood and learning, such as serotonin, GABA, dopamine, and norepinephrine. For example, over 90% of serotonin receptors are in your gastrointestinal tract. Serotonin is a neurotransmitter or chemical messenger that impacts our mood, sleep, and appetite. (Carpenter, 2012)


What’s especially fascinating is the bacteria in our gut, called the microbiome, can affect the activity of these neurotransmitters. Our gastrointestinal tract is full of bacteria that help us digest the food we eat. The composition of bacteria in every person’s microbiome is unique and can have a profound impact on brain chemistry. For instance, altering the composition of our gut flora through the use of probiotics or antibiotics has been shown to influence behavior in laboratory animal studies. Inflammation in the gastrointestinal tract caused by the release of signaling proteins called cytokines has been linked with the development of anxiety and depression. (Clapp, et. al., 2017)


And our psychological state affects the health of our microbiome. Stress and anxiety can suppress healthy microorganisms in our digestive tract and promote the growth of harmful bacteria that interfere with nutrient absorption and interact with our immune system to cause inflammation. (Harvard Health, 2019) The two-way connection between our digestive system and brain via our microbiome has been called the ‘microbiome-gut-brain axis’. (Carpenter, 2012)


A Gut Reaction


A second way our brain and spinal cord communicates with our gut is through the vagus nerve. When we’re not under stress, the vagus nerve interacts with the parasympathetic nervous system or ‘rest and digest’ response that promotes feelings of relaxation, slows our heart rate, and facilitates digestion. The vagus nerve also carries information from the stomach and intestines back to the brain to keep it informed of feelings of hunger and how quickly food is moving through the stomach. (Gould, 2019)


Of course, when we’re anxious or in distress, the digestive process is interrupted. Anxiety triggers the release of stress hormones and the sympathetic nervous system’s ‘fight-or-flight’ reaction. When our body is in fight-or-flight, our pulse and breathing quicken and blood flows away from the stomach to major muscles. Digestion decreases or grinds to a halt so the body can redirect its energy into responding to the perceived danger. (Harvard Health, 2019) This is one of the reasons that anxiety can cause unpleasant gastrointestinal symptoms such as abdominal pain, constipation or diarrhea, and bloating. The relationship between psychological stress and gastrointestinal problems is bidirectional: gastrointestinal issues aggravate anxiety and stress, and vice versa. (Blanchard, et. al., 2008)


Food for Thought


The gut-brain connection means it’s important to consider digestive health when managing our mental wellbeing during recovery. As we better understand the role of our microbiome on our mood, research suggests a diet that promotes healthy gut flora can have a positive impact on your mental wellness. (Selhub, 2015). A gut-healthy diet includes:


· Increasing consumption of fruits, vegetables, and whole foods

· Eating less processed foods that contain preservatives and food additives

· Reducing the amount of refined carbohydrates and simple sugars

· Incorporating natural probiotics like yogurt to promote healthy gut bacteria

· Replacing red meat with leaner alternatives like fish and chicken


In addition to adopting a diet that can support healthy gut bacteria, certain foods indirectly impact neurotransmitters that affect mood and anxiety. For example, the amino acid tryptophan serves a precursor to the synthesis of serotonin. Several studies have demonstrated that eating foods rich in tryptophan such seeds & nuts, egg whites, and soy products can have a positive effect on mood and energy level compared to a low tryptophan diet. (Lindseth, 2015) Omega-3 fatty acids EPA and DHA found in fish like salmon and mackerel also have been touted for their anxiety reducing properties. A meta-analysis of 19 clinical trials found fish oil had the greatest benefit for patients with preexisting anxiety symptoms at dosages of 2000 mg/day. (Su, et. al., 2018)


Everyone’s microbiome is unique, which is why it's valuable to keep a food log to track the connection between how you feel and what you eat. Especially if you have an underlying condition that’s worsened by anxiety or stress, understanding those foods that minimize associated gastrointestinal symptoms is essential. And of course, talk to your doctor before starting any new diet. Many people have found that by transforming what they eat, they also see positive changes in their mood.

Sources


Blanchard EB, et al. (2008). The role of stress in symptom exacerbation among IBS patients. Journal of Psychosomatic Research. Vol. 64, No. 2, pp. 119–28. Available at www.ncbi.nlm.nih.gov/entrez/query.fcgi


Carpenter, S. (2012). That gut feeling. Monitor on Psychology. American Psychological Association. Vol 43 (8). Available at https://www.apa.org/monitor/2012/09/gut-feeling


Clapp, et. al. (2017). Gut microbiota’s effect on mental health: the gut-brain axis. Clinical Practice. 7(4): 987.


Gould, K. (2019). The vagus nerve: your body’s communication superhighway. LiveScience. Available at https://www.livescience.com/vagus-nerve.html


Hadhazy, A. (2010). Think twice: how the gut's "second brain" influences mood and well-being. Scientific American. Available at https://www.scientificamerican.com/article/gut-second-brain/


Harvard Medical School. (2019). Harvard mental health letter: stress and the sensitive gut. Available at https://www.health.harvard.edu/newsletter_article/stress-and-the-sensitive-gut


Lindseth, G., Helland, B., & Caspers, J. (2015). The effects of dietary tryptophan on affective disorders. Archives of Psychiatric Nursing, 29(2), 102–107. doi: 10.1016/j.apnu.2014.11.008


Selhub, E. (2015). Nutritional psychiatry: your brain on food. Harvard health blog. Available at https://www.health.harvard.edu/blog/nutritional-psychiatry-your-brain-on-food-201511168626


Su K, Tseng P, Lin P, et al. (2018). Association of use of omega-3 polyunsaturated fatty acids with changes in severity of anxiety symptoms: a systematic review and meta-analysis. JAMA Netw Open.1(5):e182327. doi:10.1001/jamanetworkopen.2018.2327



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