How Your Gut Health Influences Your Mental Health
Did you know that your mental health is affected by the health of your gut?
The “gut-brain axis” describes the direct line of communication between our GI and central nervous systems. The brain communicates with the gut through endocrine- and neurotransmission to facilitate intestinal function, gut reflexes, and immune activation.
While our brains mediate the health and function of our gut, the state of our gut health can also affect our brains.
The gut microbiome refers to the community of bacteria that live in our GI tract. There are hundreds of species of bacteria in our gut, and they all contribute to proper gut function. These bacteria promote regular bowel movements, help make nutrients like vitamin K, and can help decrease inflammation. The key to reaping these benefits, however, is to maintain steady growth and balance of a variety of bacteria. Gut dysbiosis refers to the imbalance of bacteria in the GI tract. This could mean having too much/not enough of certain species or growth of the wrong types of bacteria.
Aside from gut health functions, bacteria within the gut microbiome produce and release metabolites that act directly on the nervous system. As bacteria digest the food we eat, they produce short-chain fatty acids (SCFAs) which can directly influence the nervous system (they also help reduce cholesterol levels by binding to LDL aka “bad” cholesterol—a win-win!). Bacteria can additionally produce compounds that act similarly to neurotransmitters.
Proteins released by the gut microbiome also influence hormone secretion. When our gut microbiome is healthy and balanced, our hormone levels are more likely to be healthy and balanced. However, dysbiosis can throw our hormones out of whack—for example higher levels of the stress hormone cortisol persist during dysbiosis. Hormone imbalance directly affects things like skin health, inflammation, and mood.
While hormones carry out their own unique functions in the body, they also influence mental health in that their presence or absence affects our emotions. Studies have shown higher likelihood for depressive symptoms and stress/anxiety in individuals whose gut microbiota are in dysbiosis. Stress hormones like cortisol impact the brain and cause us to feel anxious or irritable, stressed, or even depressed. A consistently unhealthy gut will consistently influence hormone balance in the body. So how do we combat this?
You can promote the health of your gut with one word: fiber. The gut microbiome thrives off of fiber—when we consume diets high in whole, high fiber foods like fruits, vegetables, whole grains, and legumes, we feed gut bacteria and allow them to produce those SCFAs, neurotransmitter-like-compounds, and proteins that influence hormone secretion.
Variation in diet is also key. Consuming the same foods each day, even if they are whole, high fiber foods will promote the growth of the same populations of bacteria, therefore allowing for an overgrowth of some bacteria and an undergrowth of others. In other words, you can still be in dysbiosis even if you eat “healthy” foods. Varying your intake is key to giving your gut the different nutrients it needs to feed a diverse population.
You’ve probably heard of probiotics and prebiotics, and these absolutely influence gut health. Probiotics are bacterial species themselves that help your already existing gut bacteria population to grow. Probiotics can be taken as supplements or eaten in fermented foods like yogurt or kimchi. Prebiotics are substances in food that we cannot digest but the bacteria in our gut can (aka fiber). Think of prebiotics as food for bacteria, and probiotics as helpers and friends. Both are beneficial and should be consumed on a balanced diet.
A recent study demonstrated that increases in dietary fiber intake were associated with decreased risk for depression and anxiety. This study was conducted in women and found that those of premenopausal age reported better moods than those of postmenopausal, likely due to higher concentrations of hormones in the premenopausal women. This study shows that the endocrine system, the nervous system, and the gut are constantly interacting. (Study Link)
This study demonstrates just some of the preliminary research that scientists are conducting to better understand the gut-brain axis in humans. More research needs to be done on this topic, but for now we know how important it is to feed our guts—a happy gut is a happy brain!
By Jessica Kaplan
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