A study from the Institute for Systems Biology shows that defecating one or two times a day correlates with better health markers. Extremes like constipation or frequent diarrhea link to underlying biological issues. Researchers examined data from 1,425 adults to reach these findings.
Researchers at the Institute for Systems Biology (ISB) published in July 2024 an analysis of bowel patterns in 1,425 adults, comparing them to genetic, biochemical, and microbiological data. They classified participants into four groups: constipation (1-2 evacuations per week), normal low (3-6 per week), normal high (1-3 per day), and diarrhea (4 or more per day). All were generally healthy, without prior diagnoses of intestinal or renal disorders.
The ideal range of 1-2 times per day showed better health outcomes, even after adjusting for age, sex, and body mass index. In diarrhea cases, upper gastrointestinal bacteria appeared in stool, alongside blood biomarkers for liver damage. For constipation, elevated levels of protein-fermenting bacteria produced toxins like indoxyl sulfate, linked to inflammation and kidney damage.
“The study shows how bowel movement frequency can influence all body systems,” explained Sean Gibbons, ISB microbiologist. Another researcher, bioengineer Johannes Johnson-Martinez, added: “After microbes consume all the fiber, they turn to fermenting proteins, generating toxins that can reach the bloodstream.”
Those in the ideal range reported higher fiber intake, better hydration, and more physical activity, with a microbiome focused on fiber fermentation. The authors suggest that changes in diet, hydration, and exercise could shift individuals toward this range, supported by a 2025 German study showing microbiome changes after eight weeks of resistance training.