Link to Study

Constipation by PULLULANASE-DRIVEN Resistant Starch Degradation and Microbiota Modulation  
https://openurl.ebsco.com/fulltext/gcd:190802929?sid=ebsco:plink:crawler-gcd&id=ebsco:gcd:190802929&crl=f&jrnl=20555008

The Core Issue

Constipation hits somewhere between 12 and 20% of people globally, and the usual fixes, laxatives or diet tweaks, often don't stick long-term. Researchers are now pointing at the gut microbiome as a likely culprit, specifically a shortage of certain bacteria that keep things moving.

The Finding

A bacterium called Ruminococcus bromii emerged as the standout player. In stool samples from constipated patients, it was significantly depleted compared to healthy controls, and it outperformed three other related species in mouse models across nearly every measure tested. The key mechanism appears to be an enzyme called pullulanase, which R. bromii uses to break down resistant starch (a type of dietary fiber that survives digestion) into short-chain fatty acids. When researchers knocked out pullulanase activity, the constipation-relieving effect dropped substantially. A small clinical trial of 34 patients given 10 grams of resistant starch twice daily for 14 days showed meaningful improvements in constipation symptoms and quality of life, with the strongest results linked to patients who had more R. bromii in their gut.

Why It Matters

This research suggests that feeding the right microbe, rather than just taking a generic probiotic, could be the smarter approach to treating chronic constipation. Resistant starch from foods like potatoes, corn, and unripe bananas has a strong safety track record, which makes this a potentially accessible intervention if the science holds up.

Limitations of Study

The clinical trial was non-randomized, which limits how confident we can be in the results. R. bromii as a live therapeutic still needs dedicated safety trials. Interestingly, combining R. bromii with Akkermansia and Bifidobacterium in mouse models did not produce any added benefit over R. bromii alone.

Interesting Statistics

• Constipated patients showed significant depletion of Ruminococcus compared to healthy controls in 16S rRNA sequencing of stool samples  
• All four Ruminococcus species tested reduced constipation symptoms in mice, but R. bromii led on water and sodium channel regulation, gut barrier integrity, and inflammation markers  
• R. bromii carries 27 glycoside hydrolase genes, consistent with its role as a heavy-duty starch degrader  
• Resistant starch supplementation significantly boosted R. bromii growth in lab conditions  
• R. bromii also raised levels of serotonin, indole, and glutamate in mouse colon tissue, and reduced anxiety-like behaviors in the same animals  
• The 34-patient trial ran for just 14 days, so long-term effects are still unknown

Useful Takeaways

Resistant starch foods like cooled cooked potatoes, green bananas, and corn are already on the shelf and carry a long safety record. If R. bromii levels in your gut are low, this type of fiber may be one way to support its growth. This is early-stage science, so treat it as a signal worth watching, not a prescription.

TL;DR

A gut bacterium called Ruminococcus bromii, which is often depleted in people with chronic constipation, appears to relieve symptoms by using an enzyme called pullulanase to ferment resistant starch into compounds that get the gut moving again.

Resistant Starch and a Rare Gut Microbe Just Teamed Up to Beat Chronic Constipation in a Clinical Trial