Probiotics: no demonstrated reduction in two markers linked to coagulation

Two markers, not a measure of cardiovascular events

High concentrations of fibrinogen and PAI-1 are associated with impaired fibrinolysis, meaning less effective clot breakdown, as well as increased cardiovascular and thrombotic risk. This association does not mean that an intervention altering these markers would automatically reduce heart attacks or thromboses.

The authors discuss a possible influence of probiotics and synbiotics on inflammatory pathways and coagulation mechanisms. This is a biological hypothesis, not evidence of cardiovascular protection. The question examined here concerns only the blood concentrations of the two markers.

What the researchers compared

The review brings together 15 randomized trials involving 892 adult participants, with no restrictions based on their health status. The trials compared oral probiotic or synbiotic supplementation with a placebo or no intervention.

The literature search covered five scientific databases through June 2025. The researchers pooled the results using a random-effects model and assessed the certainty of the evidence using the GRADE approach. The available abstract does not detail the formulations, doses or trial durations, so it cannot identify a preferred product or supplementation regimen.

No significant reduction, but uncertainty remains

The pooled results show no statistically significant reduction in fibrinogen or PAI-1. Subgroup analyses and meta-regression also found no significant variation in the effect according to the characteristics examined.

This result does not prove that all formulations are ineffective in all populations. The authors rate the certainty of the evidence as low because of inconsistent results across trials and a lack of precision. The review therefore does not demonstrate a benefit, but it does not definitively settle the question for a particular formulation or patient group.

For a purchasing decision, this distinction matters: the study provides no strong basis for choosing a probiotic or synbiotic to reduce these two markers. Nor does it support a claim that these supplements prevent cardiovascular events.

A review to read with its limitations in mind

The review was not prospectively registered. It was registered after completion, on September 5, 2026. This timing limits the ability to verify that the analyses had been defined before the results were examined.

Only the PubMed abstract provided in the dossier was consulted, not the full text. Funding, conflicts of interest and safety data have not been verified. The dossier lists a publication date of October 7, 2026, which is distinct from the literature search cutoff date.

What we can take away

This meta-analysis does not demonstrate that probiotics or synbiotics lower fibrinogen or PAI-1. With low-certainty evidence and results limited to biomarkers, a promise of cardiovascular protection would go beyond the available data.