In the first research to look at constipation's impact on the ageing brain, scientists have found some concerning links.
Being chronically constipated, defined by the authors as having a bowel movement only every three or more days, has been linked with a 73 percent higher risk of subjective cognitive decline, according to research presented Wednesday at the Alzheimer's Association International Conference in Amsterdam.
"Our study provided first-of-its-kind evidence that examined a wide spectrum of bowel movement frequency," said Dr Chaoran Ma, the research's first author and assistant professor in the department of nutrition at the University of Massachusetts Amherst, via email. "We were surprised at how strong the associations were, especially for those with very infrequent bowel movements."
About 16 percent of the worldwide adult population experiences constipation, but it's even more common among older adults due to age-related factors such as lack of exercise and dietary fibre, and the use of medicines that can cause constipation as a side effect.
Chronic constipation has been linked with inflammation and mental disorders such as anxiety and depression, but there have been many unanswered questions about the relationship between digestive health and long-term cognitive function, according to a news release.
Cognitive function refers to a person's mental capacity for learning, thinking, reasoning, problem-solving, decision-making, remembering and paying attention.
To find clues to these queries, the authors assessed more than 112,000 adults who had participated in the Nurses' Health Study, Nurses' Health Study II and Health Professionals Follow-Up Study. The first two studies investigated risk factors for major chronic diseases among women in North America, while the latter study is looking into the same topics but for men. The authors of the latest research collected data on participants' bowel movement frequency from 2012 to 2013, participants' self-assessments of cognitive function between 2014 and 2017, and details on some participants' objectively measured cognitive function between 2014 and 2018.
Compared with people who pooped once a day, constipated participants had significantly worse cognition equivalent to three years more of chronological cognitive ageing, the authors found. Increased risk was also found among those who pooped more than twice daily, though these higher odds were small.
"The more we learn about gut-brain access, the more we understand that it's just so important to ensure that (preventing or addressing cognitive decline) is a system approach," said Maria C. Carrillo, chief science officer of the Alzheimer's Association, who wasn't involved in the research. "The brain is not completely isolated from what's happening in your blood flow."
Bowel movements and the brain
This research wasn't "designed to test the causal relationship between bowel movements, the gut microbiome and cognitive health, so we cannot firmly draw conclusions regarding the precise causal sequence underlying this association," Ma said.
But bowel movement frequency and subjective cognitive function were also linked with the participants' gut microbiomes, the authors found. Among those with infrequent bowel movements and worse cognitive function, there was a depletion in good bacteria that produce butyrates, fatty acids which support the gut barrier that prevents bacteria and other microbes from entering your bloodstream, according to the Cleveland Clinic.
Butyrates also significantly aid in digestive health by providing the main energy source for colon cells. Those can be found in high-fibre foods, fibre supplements, prebiotics and full-fat dairy products — eaten in moderation — such as butter, cheese, milk or ghee. Ghee is clarified butter, made by isolating pure butterfat from the milk solids and water in butter.
Those who pooped twice or more per day and had worse cognitive function had a higher amount of species that promote inflammation and are related to dysbiosis, an imbalance in gut microbes associated with disease.
Other research presented at the same conference Wednesday had similar findings. In one abstract of 140 middle-aged adults, having lower levels of neuroprotective gut bacteria Butyricicoccus and Ruminococcus was associated with elevated levels of Alzheimer's disease biomarkers.
In another, of more than 1000 adults, those with poor cognition had abnormally high amounts of the bacteria Alistipes and Pseudobutyrivibrio compared with other participants. Alistipes bacteria have previously been linked with anxiety, chronic fatigue syndrome, depression and hypertension.
"It makes sense that individuals that are having those movements so much less frequently are going to have less of the good bacteria and more of the bad bacteria that's caused by inflammatory conditions," Carrillo said.
"Further studies are needed to identify the microbes involved, and their function," Ma said concerning her research.
Regarding neurological and digestive health, "good food not only feeds our brain, but it also promotes healthy bowel movements," Carrillo said.
Eating enough fibre from vegetables, fruits, whole grains and nuts can prevent constipation. Total fibre intake should be at least 25 grams per day, according to the US Food and Drug Administration. And being hydrated enough softens stool so you can pass it without straining.
Exercising at least a few times per week and managing stress can also help.
CNN
