Bowel movement frequency linked to long-term health, study suggests

We all poop, but not every day. And according to a new study from the Institute for Systems Biology (ISB), how often you poop may be related to your long-term health.

The ISB-led research team looked at clinical, lifestyle and multi-omics data from more than 1,400 healthy adults. They found that bowel movement frequency can have a significant impact on a person’s physiology and health. Cell Report Medicine July 16th.

The researchers looked at data from consenting participants at the consumer health products company Arrivail. The team focused on generally healthy adults and excluded people with certain health conditions or taking medications.

The research team categorized self-reported bowel movement frequency into four groups: constipation (one to two bowel movements per week), low-normal (three to six bowel movements per week), high-normal (one to three bowel movements per day), and diarrhea.

After classification, the team looked for associations between stool frequency and factors such as demographics, genetics, gut microbiota, blood metabolites and plasma chemistry.

The study showed that age, sex, and body mass index (BMI) were significantly associated with bowel movement frequency. Specifically, younger people, women, and those with a lower BMI were more likely to have lower bowel movement frequency.

Previous studies have found that bowel movement frequency can have a significant impact on the functioning of the gut ecosystem. Specifically, if stool remains in the intestine for too long, microbes use up all the available dietary fiber and ferment it into beneficial short-chain fatty acids. The ecosystem then switches to fermenting proteins, producing several toxins that can enter the bloodstream.

Johannes Johnson Martinez, lead author of the study

Indeed, the researchers also showed that the microbial composition of study participants’ gut microbiome was a clear indication of bowel movement frequency. Fiber-fermenting gut bacteria, which are often associated with health, appeared to thrive in the “Goldilocks zone” of bowel movement frequency, i.e., one to two bowel movements per day. However, protein-fermenting and upper gastrointestinal tract-associated bacteria tended to be more prevalent in patients with constipation and diarrhea, respectively.

Similarly, several blood metabolites and plasma chemistries showed significant associations with bowel movement frequency, suggesting a potential link between gut health and chronic disease risk. Specifically, microbial protein fermentation by-products known to damage the kidney, such as p-cresol sulfate and indoxyl sulfate, were more abundant in the blood of individuals with constipation, whereas clinical chemistries associated with liver damage were more abundant in the blood of individuals with diarrhea.

Notably, blood indoxyl sulfate concentrations were significantly associated with decreased renal function, providing preliminary support for a causal relationship between stool frequency, gut microbial metabolism, and organ damage in this healthy cohort.

Not surprisingly, those who reported eating a diet high in fiber, improving hydration, and exercising regularly were more likely to have good bowel movements.

“Chronic constipation has been associated with the progression of chronic kidney disease in patients with neurodegenerative and active disease,” said Dr. Sean Gibbons, Associate Professor at ISB and corresponding author of the paper. “However, it has been unclear whether bowel abnormalities are an early contributing factor to chronic disease and organ damage, or whether these retrospective associations in sick patients are simply coincidences.”

“Here we find that in a generally healthy population, constipation in particular is associated with blood levels of microbial-derived toxins known to cause organ damage before disease is diagnosed,” Gibbons said.

The study also investigated the association between bowel frequency and anxiety and depression, showing that mental health history was associated with bowel frequency.

“Overall, this study shows that bowel frequency can affect every organ in the body, and that abnormal bowel frequency may be an important risk factor for the development of chronic disease,” Gibbons said. “These findings may inform strategies to manage bowel frequency to optimize health and wellness, even in healthy populations.”