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Constantly Constipated? It Could Be Bad for Your Brain

New research highlights the connection between gut health and brain health


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The state of your digestive health may hold a few clues to your brain health, according to new research presented at the 2023 Alzheimer’s Association International Conference. Scientists are learning that everything from the frequency of your bowel movements to the type of bacteria in your gut could affect thinking and memory skills as you age, adding to a growing body of evidence that taking care of your brain requires more than just a neck-up approach.

“Our body systems are all interconnected,” Heather M. Snyder, vice president of medical and scientific relations at the Alzheimer’s Association, said in a news release. “When one system is malfunctioning, it impacts other systems. When that dysfunction isn’t addressed, it can create a waterfall of consequences for the rest of the body.”

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In one study presented at the conference, a team of researchers led by Chaoran Ma, M.D., with the University of Massachusetts Amherst, found a link between constipation and worsening cognition — the ability to think, learn and reason.

Looking at three different studies of more than 110,000 people combined, the researchers found that people who went three days or longer without pooping had “significantly worse cognition” (the equivalent of three years of additional aging) compared to people who had a bowel movement every day.

Ma says the researchers also found that bowel movement frequency was “tightly linked to the gut microbiome,” or the community of bacteria and other microbes living in the digestive system that aid with digestion and other important functions throughout the body. Levels of specific types of microbes — for example, fewer bacteria responsible for digesting fiber and fewer bacteria that produce a substance known as butyrate, which is a fuel source for gut cells — were associated with worsening cognition.

About 16 percent of U.S. adults experience constipation, according to the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK), and that percentage more than doubles when it comes to adults 60 and older. A number of age-related factors can contribute to constipation, including medication side effects, dehydration and decreased physical activity. (To put it bluntly, movement gets things moving.)

While the brain may seem distant from your gut, emerging research shows that the two are connected and in constant communication. That means that what’s happening in one can impact the other. “And there's no doubt that anything and everything that helps us clear toxins from our body is very important,” says Maria C. Carrillo, chief science officer for the Alzheimer’s Association. “That includes urine and that includes, of course, your stool. So, all of this makes sense.”

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The takeaway, Ma says, is to talk to your doctor if you are experiencing frequent constipation. It’s possible a small change in your diet or medication regimen could remedy the situation. “We should watch for symptoms of abnormal intestinal function, especially constipation, in older individuals, as these symptoms may hint at a higher risk of cognitive decline in the future,” Ma says.

Can gut bacteria affect your risk for Alzheimer’s disease?

Another study presented at the conference on July 19 found a link between low levels of specific gut bacteria and elevated levels of the proteins amyloid and tau, which are defining features of Alzheimer’s disease.

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Looking at fecal samples and cognitive measures from 140 middle-aged individuals from the Framingham Heart Study, researchers found that higher levels of amyloid and tau (detected by brain scans) were associated with lower levels of the bacteria Butyricicoccus and Ruminococcus, and higher amounts of the bacteria Cytophaga and Alistipes.

The findings suggest that the buildups Alzheimer’s biomarkers amyloid and tau in middle-aged, cognitively healthy individuals “are associated with changes in the gut microbiome structure and function,” says lead researcher Yannick Wadop, from the Glenn Biggs Institute for Alzheimer’s and Neurodegenerative Diseases at UT Health San Antonio. They also suggest that “manipulating or monitoring the abundance of bacteria with neuroprotective effects could contribute to Alzheimer’s risk reduction,” Wadop adds.

More research is needed to better understand the connection between the microbiome and the brain, Wadop says. (The Alzheimer’s Association is looking into how behavioral changes impact the gut bacteria and how that relates to brain health, with its large U.S. POINTER study.) In the meantime, there are a few things individuals can do help keep the community of microbes in their gut healthy and happy. 

Diets high in fast food, sugar, processed foods and alcohol can decrease gut health, according to the Mayo Clinic. Instead, opt for high-fiber foods like fruits, vegetables and legumes. These foods are also associated with better brain health, according to a report on nutrition and brain health from AARP’s Global Council on Brain Health. Fermented foods, like sauerkraut, kimchi and yogurt with live cultures, are good for the gut, too. 

And don’t forget: “Everything that happens to our body below the neck is very closely tied to what happens in our brain,” Carrillo says, adding that taking a more holistic approach to our overall health is key.

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