The Gut-Brain Link: You Are What You Eat   

4 min read  |  March 15, 2022  | 
Disponible en Español |

That old adage — you are what you eat — is proving to be more accurate than expected.

A growing body of medical literature ties the bacteria inhabiting our gut to many of our brain functions. One recent study, published in JAMA Neurology, links our gut microbiome to cognitive function.

Michele Marrero Alfonso, M.D., a neurologist with the University of Miami Health System, is not surprised by the findings. She points to previous research that shows how our digestive system can have an outsized influence on the rest of the body.

This study confirms some of what we already know, but it’s different. The sample is more diverse.

Dr. Marrero Alfonso

It’s also the first time such evidence has been collected in a real-world setting.

Researchers examined data collected for the 2015-16 CARDIA— Coronary Artery Risk Development in Young Adult — study. This sizeable cross-sectional program included 3,358 Black and white participants living in four urban areas. All were offered cognitive tests as part of the study, and 3,124 completed at least one assessment. The research team then recruited 615 of those adults for a microbiome sub-study that included the completion of six cognitive tests and DNA sequencing of a stool sample.

In addition, researchers factored in socioeconomic variables, such as smoking habits, physical activity, diet, and medications — all variables that can affect how our brain functions and the composition of our gut microbiota.

The team also adjusted for comorbidities, such as hypertension and diabetes.

More importantly, the study provides hope for neurologists like Dr. Marrero Alfonso, who specialize in memory and cognitive disorders and foresee a tsunami of cases as the population ages.

“We know that the incidence and prevalence of dementia is growing rapidly and is expected to almost triple by 2050,” she adds. “Right now, treatment is limited, so there is a lot of interest in prevention. One of those areas is in improving nutrition.”

Currently, the Centers for Disease and Control Prevention estimates that about 6 million Americans have Alzheimer’s disease, the most common form of dementia. In the U.S., minority groups bear a larger burden. Among Hispanics, cases are expected to increase seven times over today’s estimates; among African Americans, cases will increase four times.

Two-thirds of Americans over age 65 with Alzheimer’s dementia are women.

The JAMA Neurology study, as well as future investigations, could point to more prevention as well as earlier diagnoses. For example, three bacteria — Barnesiella, Lachnospiraceae, and Akkermansia — had a positive association with cognitive test scores, while the bacteria Sutterella appeared to result in lower scores in one assessment test.

This is the kind of information healthcare professionals might be able to use for better treatment.

But Dr. Marrero Alfonso warns that middle-aged and older people shouldn’t rush out to find supplements that include the “good” bacteria.

“What I tell my patients is that no one supplement will do everything for you,” she says. “A lot of research still needs to be done.”

In the meantime, there are modifiable risk factors that you can control.

Here are her suggestions:

Monitor your vascular health.

“Anything that damages your blood vessels – blood pressure, diabetes, high cholesterol — affects the brain because it decreases the blood to the brain,” Dr. Marrero Alfonso explains. (After Alzheimer’s, vascular dementia is the second most common form of dementia.)

Exercise, exercise, exercise.

Studies of middle-aged and older adults have repeatedly shown that aerobic exercise (exercise that increases your heart rate) leads to improvements in thinking and memory.

Eat a nutritious diet.

Dr. Marrero Alfonso recommends the DASH diet and the MIND diet.

The DASH (Dietary Approaches to Stop Hypertension) plan is heavy in fruits, vegetables, whole grains, and low-fat dairy foods but limits sugar-sweetened foods and beverages, red meat, and added fats.

MIND (Mediterranean Intervention for Neurodegenerative Delay) is similar. It discourages pastries and sweets, fried foods, and cheese while encouraging green leafy vegetables, beans, berries, and olive oil as the main cooking oil.

Get your Zzzz’s.

Studies show that insufficient sleep is linked to a higher likelihood of developing dementia.

Stay socially active.

“Social interaction at any age is good for your brain health,” Dr. Marrero Alfonso says. A 2018 study showed that just one hour of socializing can significantly reduce agitation levels in people with dementia.

Never stop learning.

Higher levels of education provide cognitive reserves.

Ana Veciana author

Ana Veciana-Suarez, Guest Columnist

Ana is a regular contributor to the University of Miami Health System. She is a renowned journalist and author who has worked at The Miami Herald, The Miami News, and The Palm Beach Post. Visit her website at or follow @AnaVeciana on Twitter.

Tags: Dr. Michele Marrero Alfonso

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