A clinical perspective for practitioners working with persistent or treatment-resistant constipation.

When someone has tried the usual approaches to constipation without much relief, it is tempting to look for one missing explanation. In practice, several factors can overlap. Transit, stool consistency, pelvic floor function, medication, diet and other health conditions may all matter.

The gut microbiome adds another layer to that picture. Methane has an established association with constipation, while recent research into bacterial breakdown of colonic mucins raises a newer question. These are related ideas, but the strength of evidence behind them is different.

For a less technical introduction, see my companion article.

Methane and intestinal transit

Methane is produced by methanogenic archaea, rather than bacteria. Higher intestinal methane levels are associated with constipation and slower transit. Experimental work suggests methane may also affect intestinal muscle activity, although it is rarely useful to treat one finding as the whole explanation for an individual patient.

That distinction matters when fibre, fluids or osmotic agents have had limited effect. It may be worth considering microbial contributions alongside the wider clinical assessment, rather than assuming that a poor response to one intervention identifies a particular mechanism.

What the mucin study found

Hamaguchi and colleagues (2026) investigated two mucin-degrading gut microbes, Akkermansia muciniphila and Bacteroides thetaiotaomicron. In their human samples, both were more abundant in people with Parkinson's disease and constipation or chronic idiopathic constipation. That is an association; it cannot establish that the microbes caused constipation in those people.

The researchers then tested a possible mechanism in germ-free mice. Mice colonised with both organisms developed constipation, whereas colonisation with either one alone did not. Altering the sulfatase activity of B. thetaiotaomicron reduced the effect in that model. This is valuable mechanistic evidence, but a result in mice does not yet tell us how often the same process contributes to constipation in people.

The authors propose a form of “bacterial constipation” involving mucin degradation and reduced stool lubrication. It is an interesting hypothesis for further human research, rather than an established diagnosis or a treatment pathway.

What we cannot infer from symptoms

Dry, hard stools, straining or a limited response to magnesium are common in constipation for many reasons. At present, those features cannot tell us that a person's colonic mucins have been depleted. Nor has a distinct “mucin-depletion constipation” subtype been validated for use in clinical practice.

The proposed mechanism should therefore not displace a careful assessment of familiar causes or become a reason to assume that a particular stool microbiome result explains a patient's symptoms.

Where this leaves practice

The research is a reminder that the microbiome may influence bowel function through more than one route. It gives us a useful question to investigate, while leaving important uncertainties: whether the mouse findings translate to people, how we might identify the mechanism reliably, and whether changing it improves patient outcomes.

For now, I would describe mucin degradation as an emerging possible contributor. Support for dietary adequacy and variety can still be considered in the usual individual context, without presenting it as a proven way to restore mucus lubrication or resolve treatment-resistant constipation.

Reference

Hamaguchi, T. et al. (2026). Bacterial constipation: Mucin-degrading intestinal commensal bacteria cause constipation. Gut Microbes, 18(1). https://doi.org/10.1080/19490976.2025.2596809