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Multi-strain probiotic reduces gastrointestinal side effects in women with elevated HOMA-IR index treated with metformin: a 12-week randomised controlled trial

Ratajczak M, Bilska A, Musialik K, Skonieczna-Żydecka K, Łoniewski I, Gogojewicz A, Karolkiewicz J

Frontiers in endocrinology, 2026

30 participants · 3 citations

Abstract

Background: Metformin is widely used as a first-line therapy for type 2 diabetes and increasingly prescribed off-label in women with elevated HOMA-IR indices, including those at risk of metabolic disorders. However, its clinical use is often limited by gastrointestinal (GI) adverse effects. The present study examined whether a multi-strain probiotic could enhance the metabolic effects of metformin and reduce GI side effects in women with newly identified elevated HOMA-IR.

Methods: In this 12-week randomised, placebo-controlled, double-blind trial, 30 women aged 25-45 years with elevated HOMA-IR (≥2.5) and no diagnosis of diabetes were enrolled. All participants were prescribed metformin 1000 mg/day. They were randomised 1:1 to receive either a multi-strain probiotic (2 × 109 CFU/day) or placebo. Outcomes included metabolic markers (glucose, insulin, HOMA-IR, RBP4, lipid profile, body composition) and self-reported GI symptoms.

Results: After 12 weeks, the probiotic group reported significantly fewer GI symptoms compared with placebo, including lower frequency of abnormal stool consistency during abdominal pain (26% vs. 52%, p < 0.05), abnormal stool frequency (18% vs. 51%, p < 0.05), and hard or lumpy stools (Bristol types 1-2; 14% vs. 26%, p < 0.05). No significant between-group differences were observed for metabolic or anthropometric parameters. Both groups showed significant improvements over time in fasting glucose (time effect p < 0.05), HOMA-IR (p < 0.05), RBP4 (p <…

How strong is the evidence?

Evidence Hub reads this as a randomized trial, done in people. Its evidence level is 2 of 5 (High · randomized trial). Randomized trials of a reasonable size are the strongest single-study design. Reported size: 30 participants or records.

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