Functional constipation: probiotic BL-99 shows a benefit in a small trial

A specific strain tested against a placebo

The researchers studied Bifidobacterium animalis subsp. lactis BL-99 in patients with functional constipation. Participants were randomly assigned to receive the probiotic or a placebo for four weeks, then followed for two weeks after stopping treatment.

The primary outcome was the change in PAC-SYM score, a 12-item questionnaire assessing constipation symptoms. Measurements were taken at baseline, at four weeks and at six weeks. The abstract states that 41 patients completed the six weeks, without clearly specifying how many were initially randomized.

Symptoms improved, but no reliable effect size is available

At four weeks, the abstract reports a statistically significant reduction in PAC-SYM scores with BL-99 compared with the placebo, particularly for abdominal discomfort and pain during defecation. Improvements were still observed two weeks after stopping treatment.

However, the numerical values in the excerpt are corrupted. They do not allow a reliable absolute effect to be reported or an assessment of whether the difference was meaningful enough for patients. The abstract also does not support conclusions about normalization of bowel transit or sustained effectiveness.

The microbiota offers a clue, not proof of the mechanism

Metagenomic analysis of stool samples also identified changes in microbiota composition and certain inferred biological functions. These observations offer a hypothesis to explain the symptom improvement, but they do not demonstrate that these changes caused it.

In particular, a change in pathways annotated as related to insulin resistance does not mean that the probiotic improves insulin resistance in patients. No clinical metabolic benefit can be inferred from this finding.

What this trial means for your choice

This finding concerns BL-99, not probiotics in general. It is therefore not enough to justify buying another product containing a different strain, even one from the same species.

The supplied abstract does not detail adverse effects, exclusions or interactions. The dose is also illegible in the excerpt. This trial provides a signal of efficacy that warrants further investigation, not a sufficient basis for recommending a protocol.

What we can take away

BL-99 appears to improve some symptoms of functional constipation in the short term. This small trial demonstrates neither a lasting benefit nor effectiveness that can be generalized to other probiotics.