Study suggests stool frequency is linked to long-term health

New research from the Institute for Systems Biology (ISB) shows that bowel movement frequency is linked to long-term health.

A team of researchers from ISB examined clinical, behavioral, and multi-omics data from more than 1,400 healthy adults. They found that bowel movement frequency can significantly impact a person’s physiology and health. The results are published in the journal Cell Reports Medicine.

The researchers analyzed data from participants in a program run by consumer health company Arivale. The study included only healthy adults, excluding those with certain medical conditions or taking medications.

Participants were divided into four groups based on bowel movement frequency: constipation (one to two times per week), low-normal frequency (three to six times per week), high-normal frequency (one to three times per day), and diarrhea. The team then looked for associations between bowel movement frequency and factors including demographics, genetics, gut microbiome, blood metabolites, and plasma chemistry.

Research results

1. Association with demographic variables: The study found that age, gender, and body mass index (BMI) were significantly associated with bowel movement frequency. Young people, women, and people with low BMI tended to have less frequent bowel movements.

2. Impact on the gut microbiome: Previous research has shown that bowel movement frequency can significantly impact the function of the gut ecosystem. If stool remains in the gut for too long, microbes use up all available dietary fiber, fermenting it into beneficial short-chain fatty acids. The ecosystem then switches to fermenting proteins, which leads to the formation of toxins that can enter the bloodstream.

The researchers found that the composition of the study participants’ gut microbiomes was an indicator of bowel movement frequency. Fiber-fermenting bacteria associated with health thrived in those with a bowel movement frequency of one to two times per day. Bacteria associated with protein fermentation or the upper gastrointestinal tract were more prevalent in those with constipation or diarrhea.

3. Associations with blood metabolites and plasma chemistry markers: The study found that several blood metabolites and plasma chemistry markers were significantly associated with bowel movement frequency, suggesting possible links between gut health and chronic disease risk. For example, byproducts of microbial protein fermentation known to cause kidney damage (p-cresol sulfate and indoxyl sulfate) were enriched in the blood of people with constipation. Chemists associated with liver damage were elevated in people with diarrhea.

4. Diet and lifestyle influences: People who reported eating a high-fiber diet, staying well hydrated, and exercising regularly were more likely to fall into the "sweet spot" for bowel movement frequency.

This study shows how bowel movement frequency can affect all body systems and how abnormalities can be an important risk factor for chronic diseases. The findings may help develop strategies to manage bowel movement frequency even in healthy populations to optimize health and well-being.

Dr Sean Gibbons, Associate Professor at the ISB and co-author of the paper, said: "Chronic constipation has been linked to neurodegenerative diseases and progression to chronic kidney disease in patients with active disease. However, until now it has been unclear whether bowel habits are early risk factors for chronic disease and organ damage or simply a coincidence in diseased patients. Here, in a healthy population, we show that constipation in particular is associated with blood levels of toxins known to cause organ damage, even before disease diagnosis."