Everyone poops, but how often people go can say a lot about their long-term health, according to research published Tuesday in the journal Cell Reports Medicine.
The study of more than 1,400 healthy adults found that people who pooped less often also showed signs of reduced kidney function. People at the other end of the spectrum, who pooped much more often than normal, showed signs of reduced liver function.
“Things like constipation are known to be associated with chronic disease,” said study co-author Sean Gibbons, an associate professor at the Institute for Systems Biology in Seattle.
What is less clear is which comes first: the constipation or the chronic disease? Does constipation at a young age cause chronic disease in otherwise healthy people, or is constipation a consequence of chronic disease?
Gibbons and his team used data from a now-defunct wellness company called Arivale to try to answer that question. The study participants were healthy, mostly white adults living in the Pacific Northwest. The researchers analyzed blood and stool samples and BMI measurements, as well as responses to questionnaires about diet and exercise habits and mental health.
From the blood samples, the team was able to detect chemicals in the blood that indicated low organ function, including poorly functioning kidneys and livers. From the stool samples, the researchers were able to genetically sequence each person’s gut microbiome, which told them about the composition of beneficial and potentially harmful microbes living there.
The researchers divided the participants into groups based on how often they went to the toilet: going to the toilet once or twice a week, going to the toilet three to six times a week, going to the toilet one to three times a day, and diarrhea, which they defined as four or more times a day.
The study found that the ideal number of bowel movements for optimal health was one or two per day. Younger people, women and those with a lower BMI tended to have fewer bowel movements. Chronic constipation — two or fewer bowel movements per week — was associated with reduced kidney function, while diarrhea — four or more times per day — was associated with reduced liver function.
Hungry microbes looking for food
The intestines are full of colonies of various microbes that feed on—and ferment—the nutrients in feces. Their favorite food is fiber, but if feces sit in the intestines too long, as is the case with chronic constipation, the microbes deplete their supply. Instead, they turn to protein, the source of which is usually the protein-rich mucus layer that lines the intestines.
“If we don’t feed our microbes, they’ll start eating us,” Gibbons said.
It creates a threefold problem: when those microbes feed on protein, they produce toxic metabolites, some of which are associated with kidney and liver dysfunction. The more bacteria rely on dietary protein sources, the more protein-preferring bacteria there will be and the fewer of the beneficial fiber-eating bacteria there will be.
Eventually, the microbes can break down the lining in their search for food, and the gut can become “leaky,” allowing bacteria and metabolites from the gut that are toxic to other organs to enter the bloodstream, where they can cause inflammation that leads to heart, liver and kidney disease, said Dr. Phillipp Hartmann, an associate professor of pediatric gastroenterology at the University of California, San Diego, who studies the interaction between the gut microbiome and other organs.
“What we can say for sure is that intestinal permeability is at least a contributing factor to disease,” said Hartmann, who was not involved in the new research. “It may not be the only factor, but it often makes disease worse.”
A similar chain of microbial events can occur when someone has diarrhea. In that case, there is a high probability that there is inflammation that damages the lining of the intestinal wall, allowing toxins to enter the bloodstream.
“When you have diarrhea or constipation, microbes build up that produce toxins that influence disease,” said Joseph Petrosino, chief of the division of molecular virology and microbiology at Baylor College of Medicine, who was also not involved in the new research.
The study found that people who regularly suffered from constipation or diarrhea had more gut bacteria that feed on protein, while people who only pooped once or twice a day had more bacteria that produce fiber.
Gibbons said it’s not clear why the study found constipation was associated with kidney dysfunction and diarrhea with liver dysfunction, but it may have to do with the fact that diarrhea prevents the intestines from absorbing bile acids — the product of cholesterol metabolism — leaving more for the liver to process. The kidneys are more affected by the metabolites produced by protein-eating gut microbes.
Because the study was not a randomized clinical trial of an intervention, the new research cannot conclude with certainty whether going to the bathroom more or less than once or twice a day is associated with chronic disease. However, Gibbons says it does seem that it may be.
“We hypothesized that we would see more of these protein-derived toxins in the blood in people who had lower bowel movements or constipation, and we did,” he said. “These things damage your liver and your kidneys.”
Petrosino says that while you can’t always control constipation and diarrhea, there are many lifestyle factors that can help keep constipation and diarrhea under control.
“First of all, it is important to eat healthy and nourish yourself with foods that contain fertilizers and promote the growth of good bacteria,” he said.
That includes eating lots of fruits and vegetables and limiting alcohol and red meat. In the study, people who reported eating a high-fiber diet, staying hydrated and exercising regularly tended to have healthier bowel movement frequencies. Probiotics may be helpful if someone is dealing with chronic conditions such as upset stomach, constipation or diarrhea, Petrosino said.
“There are probiotics that may help normalize things, but if you’re already healthy, I wouldn’t go taking them,” he said. “Don’t fix what ain’t broke.”