University of South Florida

USF Health studies how diet affects gut, oral microbiomes linked to brain health in older adults

The new research may help identify measures to prevent or delay mild cognitive impairment and dementia

Can what you eat influence the health of your brain now and in the future?

That is a key question that USF Health Morsani College of Medicine researchers hope to answer with the help of a noninvasive Microbiome in the Aging Gut and Brain (MiaGB) study.

The new clinical study expects to enroll 400 adults ages 60 and older in the Tampa Bay region and beyond — both those who are cognitively healthy as well as those diagnosed with mild cognitive impairment and early-stage dementia.

The researchers will analyze the composition of bacteria in stool samples and saliva samples (oral swabs) donated by study participants one time at the beginning of the study and then once a year for at least five years. They will track alterations over time in the populations of oral and gut microorganisms, collectively known as the microbiome. Using an interactive mobile app, study participants will complete a daily dietary recall questionnaire and yearly tests of their memory, speed of thinking, and other cognitive abilities.

“We want to know, based on changes in the microbiome ‘signature’ from the saliva and stool samples, if we can predict an older person’s risk of developing cognitive decline or dementia. And can we do that early enough to delay or prevent those age-related diseases – either by modifying the individual’s diet or the microbiome itself,” said Hariom Yadav, PhD, an associate professor of neurosurgery and brain repair at the Morsani College of Medicine and director of the USF Center for Microbiome Research.

Several studies have correlated healthy guts, characterized by a well-balanced diversity of microorganisms, with healthy aging. Alzheimer’s disease and other dementias are among the growing number of medical conditions linked to an imbalance of microorganisms (more bad bugs than good bugs) within the intestines. Emerging evidence also suggests that oral health and brain health are interconnected, including a large National Institute on Aging study last year linking gum disease with dementia.

Hariom Yadav and Shalini Jain

Hariom Yadav, PhD, (standing) and Shalini Jain, PhD, are faculty members at the USF Center for Microbiome Research, based in the USF Health Morsani College of Medicine. Their research focuses on the gut-brain connection (gut-brain axis) in relation to cognitive function.  — Photo by Allison Long, USF Health Communications and Marketing

The daily food intake logged by study participants will indicate any deficiencies in their usual diets, said Shalini Jain, PhD, the MiaGB study’s IRB principal investigator and USF Health assistant professor of neurosurgery and brain repair. “We’ll be able to evaluate the effects that certain types of foods (i.e, protein, fruits, vegetables, dairy, carbohydrates, fermented foods, and junk food) have on the growth of certain types of bacteria and see how the mix of bacteria changes if the diet is modified.”

Study participants may benefit by learning more about the calories and nutritional balance (or imbalance) in their diets, Dr. Jain added. Based on the dietary information reported, the mobile app suggests healthy habits that can be incorporated into the individual’s lifestyle.

Ronald Day and his wife Ardell, both 74, were among the first to enroll in the MiaGB study after attending a presentation about the USF Health microbiome research. Day, a retired pastor and volunteer chaplain at his Tampa continuing care retirement community, said he was intrigued by the idea that populations of microorganisms in the gut may affect cognitive skills controlled by the brain.

“On a practical level, I’m hoping to learn something about my eating habits from the food diaries we keep that might indicate what foods I should add to my diet, or which to avoid,” Day said. “And in the future, I’m hoping researchers learn enough from studies like this to suggest individualized diets (or other interventions) tailored to our own microbiomes.”

As someone in “the last third of life,” Day added, he’s keenly aware of the need to prevent or delay cognitive decline. “One of our neighbors is in the early stages of Alzheimer’s disease, and it’s been difficult for the family… Anything that can help maintain mental acuity as we age is so important.”

synbiotics yogurt

Photo by Allison Long, USF Health Communications and Marketing

Aging is not a disease, Dr. Yadav emphasized, but as people age it’s particularly important to keep a healthy balance of intestinal microbes so that a potentially harmful strain of bacteria does not overgrow and monopolize the food source of beneficial bacteria. “A healthy gut allows you to adequately absorb the healthier nutrients and keep a check on the stimulation of inflammation, which is a root cause of several age-related conditions, including abnormal cognitive function,” he said.

For more information about the MiaGB study, please email or call (813) 974-6281.

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