Your microbiome—the diverse population of microbes (bacteria) that live in your gastrointestinal (GI) tract—plays an important role in the health of your gut, and in other aspects of your physical health, from inflammatory skin disorders to obesity.1 Researchers now say that this role of promoting good health may extend to include the health of your brain and neurological systems.

What’s the Connection?

The thousands of different types of both “good” and “bad” bacteria that populate the microbiome normally exist in a balance in favor of beneficial bacteria that help prevent overgrowth of bad bacteria that can harm your heath. Studies have shown there is potential harm associated with an imbalance in the microbiome due to inflammation, intestinal permeability or lack of bacterial diversity, any of which may be associated with an overgrowth of unhealthy bacteria. In some cases, researchers are confronted with the classic “chicken or egg” question with respect to the association between gut bacteria and poor health, in terms of which comes first. Does an overgrowth cause the disorder or does the disorder cause an overgrowth of bad bacteria?

Bacteria on the Brain

Current thinking in the field of neuropsychology and the study of mental health problems includes strong speculation that bipolar disorder, schizophrenia, and other psychological or neurological problems may also be associated with alternations in the microbiome. Researchers speculate that any disruption to the normal, healthful balance of bacteria in the microbiome can cause the immune system to overreact and contribute to inflammation of the GI tract, in turn leading to the development of symptoms of disease that occur not only throughout your body, but also in your brain.2,3,4

This system of connections and communication between the gastrointestinal tract and the brain is referred to as the “gut-brain axis.” Some researchers speculate that infections occurring in early life could negatively affect the mucosal membrane in the GI tract, disrupting the gut-brain axis, and interfering with normal brain development. The mucosal membrane can also be altered in other ways, such as through poor diet choices, radiation treatment, antibiotic use, and chemotherapy.3,4

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What You Can Do

To maintain or restore the health of your microbiome and support good overall health, it is important to maintain a strong balance in favor of beneficial bacteria in your digestive tract. The first step is to eat a well-balanced diet that includes foods with probiotic or prebiotic ingredients that support microbial health by helping to restore balance to the gut microbiome.3,4 These are foods that contain live beneficial (probiotic) bacteria and, in the case of prebiotics, contain substances like specific types of fiber that nurture the growth of probiotic bacteria.

Probiotic Foods

Until more is known, look to a variety of readily available probiotic foods that supply varying amounts beneficial live bacteria that grow during carefully controlled fermentation processes. Some of these are common foods you may already be including in diet, while others may seem a bit more exotic, though they are readily available in supermarkets. Probiotic foods and beverages include plain yogurt, kefir, cottage cheese, fresh sauerkraut, kimchi, kombucha, apple cider vinegar, and miso. Keep in mind that the probiotic effects of these foods are destroyed by cooking, processing, or preserving at high temperatures.

Prebiotic Foods

Unlike probiotic foods, prebiotic foods do not contain living organisms. They contribute to the health of the microbiome because they contain indigestible fibers that ferment in the GI tract, where they are consumed by probiotic bacteria and converted into other healthful substances. Prebiotic foods include artichokes, leeks, onions, garlic, chicory, cabbage, asparagus, legumes, and oats.

Commercial Supplements

While probiotic supplements have been shown to improve symptoms of depression, anxiety, obsessive-compulsive disorder and other psychological and neurological conditions, their use should be discussed with a physician or mental health care provider. Currently, there are no standardized recommendations because researchers have yet to determine which bacterial species or combination of species, doses and delivery systems can best help treat specific symptoms and maintain overall health. It is still unclear whether single strains of probiotic bacteria are as effective as mixtures of different strains, and if or how any combination of bacteria in a supplement can interfere with other medications or other aspects of health.5

Microbial Transplant

Food and supplements represent the most common ways probiotics can be delivered to the gastrointestinal tract, but they are not the only way. Another form of treatment currently under investigation is known as fecal microbial transplant, which is pretty much what it sounds like. In short, fecal matter (stool) from a healthy individual is transplanted to the bowel of someone with a chronic condition, with the goal of repopulating their microbiome with more diverse species of bacteria and reducing symptoms. This technique has been shown to be effective in treating gastrointestinal disorders but studies into its value for psychiatric symptoms are in very early stages.6

Looking Ahead

The majority of studies looking at the gut-brain axis and the use of probiotics to reduce symptoms and occurrence of mental health disorders such as bipolar and schizophrenia are preliminary, preclinical studies that support the theory but have yet to demonstrate an absolute effect in humans with mental health issues. Although early research points to positive outcomes, larger population, and human clinical studies are necessary to determine which patients can truly benefit from probiotic or “psychobiotic” treatment of mental health disorders, and how these treatments can best be applied.7

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