Effect of Vitamin D Supplementation on Primary Dysmenorrhea: A Systematic Review and Meta-Analysis of Randomized Clinical Trials

Dysmenorrhea causes pain and inconvenience during menstruation. In addition to medication, natural compounds are widely used to relieve various types of pain. In this study, we aimed to assess the effects of vitamin D (vit. D) supplementation in relieving the symptoms of primary dysmenorrhea. A comprehensive systematic database search of randomized controlled trials (RCTs) was performed. Oral forms of vit. D supplementation were included and compared with a placebo or standard care. The degree of dysmenorrhea pain was measured with a visual analogue scale or numerical rating scale. Outcomes were compared using the standardized mean difference (SMD) and 95% confidence intervals (CIs) in a meta-analysis. RCTs were assessed using the Cochrane risk-of-bias v2 (RoB 2) tool. The meta-analysis included 8 randomized controlled trials involving 695 participants. The results of the quantitative analysis showed a significantly lower degree of pain in the vit. D versus placebo in those with dysmenorrhea (SMD: −1.404, 95% CI: −2.078 to −0.731). The results of subgroup analysis revealed that pain lessened when the average weekly dose of vit. D was over 50,000 IU, in which dysmenorrhea was relieved regardless of whether vit. D was administered for more or less than 70 days and in any dose interval. The results revealed that vit. D treatment substantially reduced the pain level in the primary dysmenorrhea population. We concluded that vit. D supplementation is an alternative treatment for relieving the pain symptoms of dysmenorrhea.