NBC News
Everyone poops, but how often people do it could reveal 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 defecated less frequently showed signs of decreased kidney function, while those who went to the bathroom more than usual showed signs of impaired liver function.
“It’s well known that problems like constipation are 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 early in life cause chronic disease in otherwise healthy people, or is constipation the result 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 samples, stool, and Body Mass Index (BMI) measurements, as well as responses to questionnaires about diet, exercise habits, and mental health.
poor functioning of organs, including the kidneys and liverFrom the stool samples, the researchers were able to genetically sequence each person’s gut microbiome, which told them the composition of the beneficial and potentially harmful microbes living there.
The ideal frequency
The researchers divided the participants into groups based on how frequently they had bowel movements: one to two bowel movements per week, three to six bowel movements per week, one to three bowel movements per day, and diarrhea, which they defined as four or more times per day.
The study found that the ideal bowel movement frequency for optimal health was one to two a day. Younger people, women, and people with a lower BMI tended to have less frequent bowel movements. Chronic constipation (two or fewer bowel movements per week) was linked to decreased kidney function, while diarrhea (four or more bowel movements per day) was associated with decreased liver function.
The importance of “feeding” our intestinal microbes
The gut is filled with colonies of different microbes that feed on — and ferment — the nutrients in stool. Their preferred food is fiber, but if stool remains in the gut for too long, as in cases of chronic constipation, the microbes deplete their supply and turn to protein, the source of which is usually the protein-rich mucus layer that lines the gut.
“If we don’t feed our microbes, they will start eating us,” Gibbons warned.
This creates a triple problem: When those microbes feed on protein, they produce toxic metabolites, some of which are associated with kidney and liver dysfunction. Additionally, as more bacteria rely on protein-derived food sources, there will be more of the protein-preferring bacteria and fewer of the beneficial fiber-eating bacteria.
Over time, microbes can begin to break down the mucous membrane in search of food, and the gut can become “leaky.”
That allows bacteria and metabolites from the gut that are toxic to other organs to spill into the bloodstream, where they can cause inflammation that leads to heart, liver and kidney disease, said Dr. Phillipp Hartmann, an assistant professor of pediatric gastroenterology at the University of California, San Diego, who studies the interaction between the gut microbiome and other organs.
“One thing we can say for sure is that intestinal permeability at least contributes 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 if a person has diarrhea, although in that case, it is likely inflammation that breaks down the mucous membrane lining the gut, allowing toxins to enter the bloodstream.
“When you have diarrhea or constipation, microbes build up and produce toxins that influence the disease,” said Joseph Petrosino, a professor of molecular virology and microbiology at Baylor College of Medicine. He also was not involved in the new research.
The study found that people who reported regular constipation or diarrhea had more protein-eating gut bacteria, while people who pooped once or twice a day had more fiber-fermenting bacteria.
Gibbons said it’s not clear why the study found that constipation was associated with kidney dysfunction and diarrhea with liver dysfunction, but it could have to do with the fact that diarrhea prevents the gut from absorbing bile acids (the product of cholesterol metabolism), leaving more for the liver to process. The kidneys are more affected by metabolites produced by protein-eating gut microbes.
Because the study was not a randomized clinical trial involving an intervention, the new research cannot conclude with certainty whether having one to two bowel movements a day is linked to chronic disease, but Gibbons said it appears that may be the case.
“We hypothesized that we would see more of these protein-derived toxins in the blood of people with lower bowel movements or constipation, and we did,” he explained. “These things damage the liver and kidneys.”
A healthy diet is key
Petrosino said that while it’s not always under people’s control, many lifestyle factors can help keep both constipation and diarrhea at bay.
“First of all, it is important to maintain a healthy diet, consuming foods that fertilize and promote the growth of good bacteria,” he said.
That includes eating plenty of fruits and vegetables, cutting back on 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 frequency. Probiotics may be helpful if a person has chronic conditions such as an upset stomach, constipation or diarrhea, Petrosino explained.
“There are probiotics that can help normalize things, but if you’re healthy, I wouldn’t start taking them,” she said. “Don’t fix what ain’t broken.”
