Functional GI Disorders, Microbes, and Brain-Gut Interactions

This article was adapted from an interview conducted with Emeran Mayer Professor of Medicine at UCLA at the 2016 Gut Microbiota for Health World Summit

Scientists are making exciting discoveries about the connection between the gut (digestive system) and brain and how that link affects a person’s health. One of the discoveries is how vital the bacteria that live in the gut, the gut microbiota, are. The gut microbiota helps with digestion, maintaining the immune system, and protecting from pathogens. If the gut microbiota is disturbed, it might lead to symptoms; for example, taking antibiotics sometimes leads to diarrhea.

The Brain and the gut talk to each other

There is a connection between what gut microbes produce and brain activity, function, and structure.

This connection begins during fetal development and is established by about three years of age. If there is an imbalance in the types of microbes in the gut, a person could be vulnerable to a functional gastrointestinal (GI) disorder. A person’s diet affects the types of metabolites gut microbes make. These microbial metabolites may influence the nervous system in the gut (the enteric nervous system) and the brain. Diet becomes an essential factor, not only for its direct effect on health but also for what it does to the microbes, what they produce, and how these metabolites affect the nervous system.

Microbial metabolites: substances produced by gut microbes by fermenting food that the human GI system cannot process or absorb. Hundreds of thousands of these metabolites are made in the gut.

The Low FODMAP diet and IBS

FODMAPs are types of carbohydrates found in foods like wheat and beans. Followers of the low FODMAP diet eat less of the fiber that supports beneficial microbes in the gut. In the short term, a diet like this may lessen symptoms for some IBS patients. Still, these diets are difficult to maintain for a long time, and they may even have adverse effects on gut microbiota. Moreover, it appears that a healthy, balanced microbiota also can alleviate symptoms. So, a low FODMAP diet may not be the best choice for managing IBS.

There is new evidence that suggests that the benefits of a particular diet depend on the gut microbial composition. We need a better idea of what a specific diet does to the gut microbes and microbial metabolites, and how these substances affect the nervous system in the gut and brain.

Learn more about the low FODMAP Diet and the affects on the gut

Mediterranean style diet

Eating a mix of complex carbohydrates, protein, and fats is essential to growing healthy gut microbes. The Mediterranean diet or similar diets probably come closest to this, with a high proportion of complex carbohydrates from plant-based foods, minimal animal fat, a relatively small amount of protein mainly from fish and chicken, and few refined sugars.

Stress can affect the GI tract

We know that feeling anxious or sad while eating can affect how the gut contracts or secretes enzymes to digest food.  In addition, we know that stress can affect the behavior of the gut microbiota directly.  An acutely stressed person or one chronically affected by sad emotions will have a different set of microbes. It seems that a balanced mind and a proper diet go hand in hand.  If a person is constantly feeling stressed, even if they incorporate a healthy diet, will not gain the same benefits as a less stressed person. 

Gut Microbes help maintain a balance between the brain and the gut

A person can take care of what, when, and how they eat to promote a healthy balance in the gut microbiome. Maintaining a positive emotional state and, as much as possible, relaxing, and enjoying mealtime will help support the gut microbes. Many simple forms of stress reduction, such as exercise, abdominal breathing, or progressive muscle relaxation, can reduce pain. Eating a sensible diet, reducing stress, and working toward a balanced body and mind are steps to improving well-being.

Gut Microbe
Emeran Mayer, MD and Cole Norton

*The 2016 Gut Microbiota for Health World Summit, organized by the American Gastroenterological Association (AGA) and the European Society of Neurogastroenterology & Motility (ESNM), took place in Miami, FL from March 5–6, 2016.

Emeran Mayer, MD is Professor of Medicine and Executive Director of the G. Oppenheimer Center for Neurobiology of Stress and Resilience at UCLA in Los Angeles, CA. Dr. Mayer is a member of the Board of Directors of IFFGD. His book, The Mind-Gut Connetion: How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choice, and Our Overall Health, is available at Amazon.

Adapted from IFFGD Publication #273 “Functional GI Disorders, Microbes, and Brain-Gut Interactions” by Cole W. Norton and Aki S. Norton, IFFGD, in collaboration with Emeran Mayer Adapted by Abigale Miller.

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