The Mind-Gut Connection: How the Hidden Conversation Within Our Bodies Impacts Our Mood, Our Choices, and Our Overall Health

by Emeran Mayer

Gut microbiota undergo major shifts in Parkinson’s patients, as demonstrated in a recent study performed by Filip Scheperjans, of the University of Helsinki, and his colleagues. The investigators found that the microbiota of Parkinson’s patients had reduced levels of Prevotella bacteria compared with the microbiota of healthy people. Perhaps not coincidentally, Prevotella flourish in the guts of people who eat a plant-based diet, and are reduced in people who eat fewer plants and more meat, milk, and dairy.

And we know gut microbial diversity wanes later in life, a period when your gut microbiome becomes more vulnerable to disturbances. Perhaps not coincidentally, Parkinson’s usually sets in after the age of sixty.

the basic dietary pattern is characterized by high consumption of monounsaturated fatty acids—primarily from olive oil—as well as daily consumption of fruits, vegetables, whole-grain cereals, low-fat dairy products, and moderate amounts of red wine; weekly consumption of fish, poultry, nuts, and legumes; and low and infrequent consumption of red meat.

Besides the high levels of protective antioxidants and polyphenols contained in olive oil and red wine, which have beneficial effects on cellular health, the anti-inflammatory effect of the Mediterranean diet on the body is most often cited. Polyphenols are plant-based compounds found in a variety of foods and beverages. Besides red grapes and olives, many other fruits and vegetables are rich sources of polyphenols, as are coffee, tea, chocolate, and some nuts.

We now know that, in addition to the high levels of complex carbohydrates in this largely plant-based diet, it is the high levels of polyphenols that exert a beneficial effect on the gut microbiota. The polyphenols not only come from the daily consumption of extra virgin olive oil; these health-promoting compounds are also contained in nuts, berries, and red wine, all of which are essential elements of the Mediterranean diet.

One of the generally agreed-upon criteria for a healthy gut microbiome has been its diversity and the abundance of microbial species present in it. As in the natural ecosystems around us, high diversity of the microbiome means resilience and low diversity means vulnerability to perturbations. Fewer microbial species means a diminished ability to withstand perturbations such as infections (by pathogenic bacteria, viruses, or the pathobionts living in our gut), poor diet, or medications.

Both habitats are dominated by lactobacilli and bifidobacteria. These bacteria can produce many antimicrobial substances, and they have the unique ability to produce enough lactic acid to create an acidic milieu that is hostile to most other microorganisms and pathogens.

it’s difficult to increase our normal level of microbial diversity, thereby increasing our resilience against disease and improving our health. No matter how many probiotic pills you swallow, how much sauerkraut and kimchi you consume, and how extreme a diet you select, your basic gut microbial composition and diversity will remain relatively stable.

We know that probiotic interventions can benefit your gut health by altering the metabolites that your microbiota produce. The impact of such a probiotic intervention on the health of your gut microbes may be greater during the first few years in life, when the microbiome is still developing, or following the decimation of your gut microbial diversity from intake of a broad-spectrum antibiotic, or during chronic life stress.

you tend to carry the same key set of species for long periods. This stability is critical for your health and well-being. It ensures that friendly gut microbes can return quickly to an equilibrium state following a stress-related perturbation, which allows them to keep up their beneficial activities over time. This makes a microbiome resilient.

no quick analysis of your gut bacterial species—for example, your ratio of Prevotella to Bacteroides, or Firmicutes to Bacteroidetes—can assess the integrity of your gut-brain axis and your health status.

We cannot expect that any simple intervention by itself, such as a particular diet, will optimize your gut microbiome, while not paying attention to all the other factors that influence gut microbial function, like the influence of unhealthy gut reactions associated with stress, anger, and anxiety at the same time.

The science now says that changing your diet is not enough. You need to modify your lifestyle as well.

gut microbial analysis from a simple stool sample could become one of the most powerful screening tools in health care. This could help detect particular diseases, or vulnerability to particular diseases, including poorly understood brain-gut disorders such as autism spectrum disorders, Parkinson’s disease, Alzheimer’s disease, and depression.

Keep in mind that pesticides used to grow GMO foods may not directly harm our human bodies, but they are likely to affect the function and health of our gut microbes and their interactions with the brain.

Such products include kimchi, sauerkraut, kombucha, and miso, to name just a few. Various fermented milk products, including kefir, different types of yogurts, and hundreds of different cheeses, provide probiotics as well. I recommend selecting low-fat and low-sugar products that are free of emulsifiers, artificial coloring, and artificial sweeteners.

Periodic fasting has been an integral part of many cultures, religions, and healing traditions for thousands of years, and prolonged fasting may have positive impact on brain functions and well-being. A popular explanation for the benefits of fasting is based on the idea that it cleanses the gut and the body by getting rid of harmful and toxic substances.

Recall that when your stomach is empty, it activates periodic high-amplitude contractions that slowly but forcefully sweep from the esophagus to the end of the colon. At the same time, the pancreas and the gallbladder secretion release a synchronized burst of digestive juices. The combined effect of this reflex, called the migrating motor complex, is analogous to a weekly neighborhood street sweeping. We don’t yet know what this street sweeping does to our gut microbes or whether it alters the metabolites they produce. There is good evidence that it removes microbes from the small intestine, where normally only a few reside, and sweeps them into the colon, where most gut microbes live.

For these reasons, scan your body and mind and tune in to your emotions before you sit down to eat something. If you are stressed, anxious, or angry, try to avoid adding food to the turmoil in your gut.

If you eat when you’re happy, your brain sends signals to your gut that you can think of as special ingredients that spice up your meal and please your microbes. I suspect that happy microbes will in turn produce a different set of metabolites that benefit your brain.

Aerobic exercise has well-documented beneficial effects on brain structure and function, ranging from a reduction in the age-related decline in thickness of the cerebral cortex, to improved cognitive function and reduced stress responsiveness.