Efficacy of probiotic supplementation in reducing primary dysmenorrhea: a double-blinded randomized controlled trial

Primary dysmenorrhea is painful menstruation in the absence of pelvic pathology, whereas secondary dysmenorrhea is menstrual pain attributable to an underlying pelvic disease (e.g., endometriosis). Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used as first-line therapy. Recent evidence ¹⁸ suggests that modulation of the gut microbiota may influence menstrual pain through immunologic and neuroendocrine pathways. This double-blinded, randomized, placebo-controlled trial investigated the efficacy of daily multispecies probiotic supplementation in reducing menstrual pain severity in women aged 18-24 years diagnosed with moderate to severe primary dysmenorrhea. Forty-eight participants were randomized to receive either a probiotic supplement or placebo for three consecutive menstrual cycles, followed by a three-month observation period. The primary outcome was the change in pain severity, assessed using a 10 cm visual analog scale (VAS). At baseline, VAS scores were similar between groups (probiotic 6.1 ± 1.17 vs placebo 6.3 ± 1.26; p = 0.62). After three months of intervention, the probiotic group demonstrated a significantly greater reduction in pain scores compared to the placebo group (3.7 ± 1.84 vs 5.8 ± 2.14; p < 0.01). However, the effect was not sustained after discontinuation of supplementation. No serious adverse events were reported. These findings suggest that continuous intake of multispecies probiotics may be an effective non-hormonal adjunct therapy for primary dysmenorrhea. Clinical trial registration: Thai Clinical Trials Registry (TCTR20230326001), registered on 22 March 2023. https://thaiclinicaltrials.org/.