Eating for Two: Your Brain and Your Gut

By Shannon Kasun, Neuroscience Specialist

The gastrointestinal tract and central nervous system are deeply intertwined. Think about the knot in your stomach before an important presentation, exam, or stressful conversation. That familiar sensation is more than a metaphor; it is a real-time example of communication between your brain and your gut.

This constant, two-way communication is known as the gut-brain axis, and emerging research suggests that it may have important implications for brain health, cognition, and healthy aging.

Embedded within the walls of your digestive tract is an enormous network of more than 100 million nerve cells known as the enteric nervous system (ENS). Its size and complexity have earned it the nickname of the “second brain.”

The ENS helps regulate digestion largely on its own, but it does not operate in isolation. Instead, the gut and brain continuously exchange information through neural, hormonal, and immune pathways. One of the major neural routes connecting the two is the vagus nerve, which provides a direct communication pathway between the brain and many of the organs involved in digestion.

There is another important participant in this conversation: the trillions of microorganisms that inhabit the gastrointestinal tract. Collectively known as the gut microbiota, this diverse ecosystem of bacteria and other microorganisms helps digest food, interacts with the immune system, and produces biologically active compounds. Researchers are investigating how these microorganisms may influence signaling along the gut–brain axis and, in turn, aspects of brain function and health.

What we eat helps determine which microorganisms thrive within the gut. Different dietary components exert unique effects on the gut microbiota. Polyphenols, for example, are naturally occurring compounds abundant in plant foods such as berries, tea, herbs, and olive oil. In addition to their antioxidant and anti-inflammatory properties, polyphenols can interact with the gut microbiota and support the growth of beneficial bacterial species. Importantly, greater microbiota diversity has been associated with enhanced cognitive flexibility and executive function (Tooley, 2020).

Dietary fiber also plays an important role. Unlike many nutrients, certain fibers escape digestion in the small intestine and travel to the colon, where gut bacteria ferment them. This process produces compounds called short-chain fatty acids (SCFAs), including butyrate, acetate, and propionate. SCFAs help maintain the integrity of the intestinal barrier, regulate immune and inflammatory activity, and may even contribute to the integrity of the blood-brain barrier, the highly selective boundary that protects the brain from potentially harmful substances circulating in the blood (Parker et al., 2019).

In this way, what happens in the gut may not necessarily stay in the gut.

The Mediterranean diet provides a useful example of how an overall dietary pattern can support this microbial ecosystem. Rich in fruits, vegetables, whole grains, nuts, legumes, and olive oil, the Mediterranean diet supplies abundant fiber, polyphenols, and unsaturated fats. Together, these components help support a diverse gut microbiota and provide substrates that beneficial bacteria can use to produce SCFAs. These microbial products may then contribute to healthier intestinal barrier function, regulation of inflammation, and immune health, all of which hold potential relevance beyond the digestive tract.

Research supports an association between Mediterranean-style eating and cognitive health. Greater adherence to the Mediterranean diet has been associated with a lower risk of mild cognitive impairment (MCI) and Alzheimer’s disease (AD) (Fu et al., 2022). The gut–brain axis represents one potential biological pathway that may help explain the observed protective associations between plant-forward dietary patterns and brain health.

The opposite pattern may also be important. Western-style diets high in ultra-processed foods, refined sugars, and certain fats have been associated with lower microbial diversity, impaired intestinal barrier function, and greater systemic inflammation. Because chronic inflammation and vascular dysfunction can also affect the brain, researchers are increasingly interested in whether the microbiome represents one of the biological links connecting long-term dietary patterns with cognitive and neurological health.

The science of the gut–brain axis is still evolving, and researchers are continuing to determine exactly how changes in the microbiome translate into meaningful differences in human cognition and brain aging. But one principle is becoming increasingly clear: supporting brain health may begin in the gut.

A diet rich in diverse plant foods, fiber, polyphenols, and unsaturated fats does more than nourish us. It also nourishes the microorganisms living within us and through the gut–brain connection, that relationship may become another important piece of building a healthier, more resilient brain.

References 

Tooley K. L. (2020). Effects of the Human Gut Microbiota on Cognitive Performance, Brain Structure and Function: A Narrative Review. Nutrients, 12(10), 3009. https://doi.org/10.3390/nu12103009 

Parker, A., Fonseca, S., & Carding, S. R. (2020). Gut microbes and metabolites as modulators of blood-brain barrier integrity and brain health. Gut microbes, 11(2), 135–157. https://doi.org/10.1080/19490976.2019.1638722 

Fu, J., Tan, L. J., Lee, J. E., & Shin, S. (2022). Association between the mediterranean diet and cognitive health among healthy adults: A systematic review and meta-analysis. Frontiers in nutrition, 9, 946361. https://doi.org/10.3389/fnut.2022.946361