A systematic review and meta-analysis of randomized clinical trials depicted that Vitamin D treatment significantly decreases pain levels in women battling primary dysmenorrhea. An extensive systematic search of randomized controlled trials (RCTs) was carried out to explore the effects of vitamin D orally in comparison with standard care or placebo in managing menstrual pain.

The intensity of dysmenorrhea pain was evaluated using numerical rating scale (NRS) or visual analogue scale (VAS), and the outcomes were analyzed through a meta-analysis utilizing 95% confidence intervals and standardized mean difference (SMD). Employing the Cochrane risk-of-bias v2 (RoB 2) tool, the RCTs were evaluated for their risk of bias.  The meta-analysis comprised 8 randomized controlled trials, encompassing a total of 695 participants.

The quantitative findings demonstrated a significant reduction in pain among those with dysmenorrhea who received vitamin D compared to the placebo group (SMD -1.404). Regardless of the duration of administration (whether for more or less than 70 days) and the specific dose interval, subgroup analysis indicated that pain relief was observed when the average weekly dose of vitamin D exceeded 50,000 IU. Based on these findings, it can be concluded that oral Vitamin D supplementation offers a viable alternative for alleviating the pain symptoms connected with dysmenorrhea.