Vitamin D for primary dysmenorrhea and endometriosis-related pain – A systematic review of registered RCTs

Abstract

Objective This systematic review investigates the potential role of vitamin D supplement in alleviating pain associated with primary dysmenorrhea or endometriosis by analysing registered randomised controlled trials (RCTs). Methods We comprehensively searched the WHO International Clinical Trials Registry Platform to identify registered RCTs that assessed the effects of vitamin D supplement on pain outcomes in people with primary dysmenorrhea or endometriosis. The primary outcomes of interest were pain severity/intensity, pain duration, pain medication usage and pain-related outcome measurements. Results Seven registered RCTs were included in this systematic review. These RCTs had diverse doses and treatment durations of vitamin D supplement used as intervention. They also had either high or some concerns of risk of bias, according to Cochrane risk of bias version 2 assessment. Substantial heterogeneities were generally observed across the seven RCTs. When measured using a validated tool visual analogue scale (VAS), pain severity was significantly lower at the end of treatment when compared with placebo (mean difference MD –1.12, 95% confidence interval [–2.16, –0.07], I2=81%, 5 studies, n = 308). This significant difference was observed in the primary dysmenorrhea RCTs, but not the endometriosis RCTs. Conclusion This systematic review identified vitamin D may reduce pain associated with primary dysmenorrhea, though a low certainty of evidence was available. Future studies that use standardised doses and treatment duration in accordance with the latest clinical practice guidelines are needed to explore any potential benefits vitamin D may have for people with these conditions.