Bad bacteria in the gut harms brain health, increase dementia risk: Study

New research presented Wednesday at the Alzheimer’s Association International Conference in Amsterdam highlights a growing body of evidence linking people’s microbiomes to their brain health.

One study found that chronic constipation was tied to worse cognitive abilities — the equivalent of three years of aging — while two other studies found that certain gut bacteria were associated with dementia risk.

All three studies, which haven’t yet been published in peer-reviewed journals, point to a possible role that a buildup of “bad” bacteria in the gut could play in cognitive health.

“We know that it is essential for overall good health to regularly eliminate waste from the body. If that does not happen, we may retain toxins that negatively impact our health in a variety of ways,” said Christopher Weber, the director of global science initiatives with the Alzheimer’s Association, who wasn’t involved with the research. “Although more research is needed, it’s a fascinating start.”

When ‘bad’ bacteria overcrowd the ‘good’

Chaoran Ma, an assistant professor of nutrition at the University of Massachusetts Amherst, led the study looking at constipation and cognitive decline, which analyzed data on bowel movements and cognition over six years from 110,000 people from three long-running studies.

People with chronic constipation — defined as having one bowel movement every three or more days — were found to have “significantly” worse cognition, equal to three years of aging, compared to those who were able to go once a day, the research found.

People with chronic constipation also had more bacteria that cause inflammation in their guts and less bacteria that break down dietary fibers, said Ma, who was a research fellow at Brigham and Women’s Hospital and Harvard Medical School in Boston when the research was completed. The research showed a correlation, not causation, meaning the study doesn’t prove constipation causes such problems.

Researchers don’t know why constipation may affect the brain that way, but they speculate that a buildup of “bad” bacteria overcrowds the “good” protective kind, Weber said.

Ma said the findings are particularly important for older adults, who are more likely to experience constipation due to lack of exercise, use of certain medications and fiber-deficient diets.

Two other studies presented at the conference, both of which were conducted by researchers at UT Health San Antonio in Texas, found that specific gut bacteria were associated with an increased risk of dementia in cognitively healthy adults. Other gut bacteria, they found, had protective effects.

Together, the findings join a growing body of data about what scientists call the gut-brain axis — the two-way communication pathway that connects the functions of the gastrointestinal tract and the brain via the nervous, immune and hormonal systems and is involved in a variety of processes, from metabolism to stress.

A better understanding of the axis could help scientists develop new ways to prevent and treat Alzheimer’s and other dementias even before symptoms emerge.

“It is important to recognize that all of our body systems are connected and work together,” Weber said. “If one of them isn’t working well and it is not properly diagnosed and treated, it can have significant consequences for the health of other areas of the body.”

Source: NBC News

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