Although there are lucky people who “go” every day, even at the same time of the day (real human clocks!), a vast majority of us experience constipation at some point in our lives: maybe when we travel, or when we are stressed, or when we change a bit our diet. Even the slightest of changes can drive the moment away for several days, causing discomfort and bloating.

A sensitive intestine? Maybe, but a new study by Japanese scientists at Nagoya University has pinpointed two potential culprits that may also cause constipation: Akkermansia muciniphila and Bacteroides thetaiotaomicron, two common bacterial species we harbor in our guts.

According to the results of a study published in the journal Gut Microbes, these two microorganisms work together to dry out the lining of the gut: they break down mucin, a slimy coating in our colon that keeps our stool moving along. With less mucin, the intestine becomes drier, the stool becomes drier and harder, and therefore more difficult to pass.

This newly discovered mechanism may explain why standard treatments for constipation often offer temporary relief, as they do not target the underlying cause. Interestingly, the discovery also opens the door to using these bacterial species as biomarkers to identify the type of constipation a person suffers from and to treat it in a personalized way. It also sheds light on how to alleviate symptoms associated with certain neurological conditions, such as Parkinson’s disease, autism or even Alzheimer’s.

 

A common problem

It is estimated that up to 10% of the global population suffers from chronic constipation, mostly women and older adults. The cause remains a mystery. There are also some diseases, like Parkinson’s, in which patients begin experiencing bowel problems even decades before developing tremors and mobility issues. In those cases, traditionally it was thought those health issues were due to nerve degeneration, but now Japanese scientists have discovered bacterial activity plays a pivotal role: Parkinson’s patients have higher levels of these mucus-eating bacteria.

In an experiment with mice, the Japanese researchers confirmed both bacteria are needed to pose a threat to mucin. B. thetaiotaomicron remove protective sulfate groups from the mucin, and then A. muciniphila breaks down and consumes the exposed mucin. Then, they modified one of the microorganisms B. thetaiotaomicron to make it incapable of degrading mucin and transplanted it together with Akkermansia into the rodents. When they did so, the animal’s colon slimy layer remained intact, and they did not show any signs of constipation.

Although it is unknown how many people may have these gut microbiota species, the results open the door to finding new treatments effective for chronic constipation, especially for people who find no relief with traditional one-size-fits-all approaches currently available on the market.

 

 

Reference:

Hamaguchi, T., Gibo, N., Ohara, M., et al. Bacterial constipation: Mucin-degrading intestinal commensal bacteria cause constipation. Gut Microbes, 18(1). https://doi.org/10.1080/19490976.2025.2596809