Two Gut Bacteria Species Linked to Constipation Mechanism

A new study pinpoints two species of bacteria that work together to dry out the lining of the gut and cause constipation. It is as unfortunate an ailment as it is ubiquitous: at some point in our life, we will become constipated. Our gut is a delicate flower, and sometimes it just can’t cope with the even slightest of changes to our diet or environment: low water intake, a lack of adequate dietary fiber, a sedentary lifestyle, medications, and more can prevent you from “going.”

Gut bacteria are crucial to ensuring healthy digestion and defecation. But two species of bacteria may also be the cause of constipation: according to a new study, Bacteroides thetaiotaomicron and Akkermansia muciniphila appear to work in concert to break down colonic mucin, the slimy coating in our colon that keeps our poo moving along. Too little mucin means a drier and more constipation-prone colon.

"What excites me most about this study is that we've identified a specific mechanism by which gut bacteria can cause constipation,” says Tomonari Hamaguchi, a lecturer at Nagoya University in Japan and lead author of the study. He notes that constipation causes some 2.5 million doctor visits every year in the U.S. “Yet for many patients, current treatments provide only temporary relief because the underlying cause remains unknown,” he says.

In the study, which was published this week in Gut Microbes, the researchers modified one of the bacteria, B. thetaiotaomicron to prevent it from breaking down mucin. They then transplanted it and the other bacterium, A. muciniphila, into mice. Interestingly, the mice’s colon mucin stayed intact. And the animals remained regular, with no signs of constipation. The findings indicate that both of the bacteria together, not just one or the other, pose a threat to mucin.

It’s unclear how widespread these bacteria are in people, but the results could open the door to new treatments for chronic constipation, especially for people who find no relief with the drugs and remedies that are already on the market. According to one estimate, as many as one in five people in North America may have chronic constipation, and it’s more common in women and older people.

“Not all constipation has the same cause, and if we can identify patients with this bacterial mechanism—for example, by measuring fecal Akkermansia levels as a biomarker—we may be able to move toward personalized treatment strategies instead of one-size-fits-all laxatives,” Hamaguchi says.