A blinded, randomized controlled trial of high-dose vitamin D supplementation to reduce recurrence of bacterial vaginosis.

Blinded randomized controlled trial in BV-positive, nonpregnant premenopausal women aged 18-50 years seen at a single urban sexually transmitted infection clinic in the United States. The population was predominantly Black, and 59 participants were randomized to the vitamin D arms across four equal-sized study arms.

Oral vitamin D3 (cholecalciferol) 50,000 IU per capsule was given as a high-dose regimen: 9 capsules at weeks 1, 2, 3, 4, 8, 12, 16, 20, and 24 after enrollment. Standard metronidazole therapy was provided alongside the trial supplement regimen; placebo served as the comparator.

Vitamin D supplementation increased serum 25(OH)D levels but did not reduce bacterial vaginosis recurrence or improve BV-free survival. At trial end, median 25(OH)D was 30.5 ng/mL in the vitamin D arm versus 17.8 ng/mL in control, yet BV prevalence at 24 weeks was 65% versus 48%. The primary intention-to-treat hazard ratio for recurrence was 1.11 (95% CI, 0.68 to 1.81), and the time-varying 25(OH)D analysis was also null (HR 1.02, 95% CI, 0.99 to 1.04). The log-rank P value for BV-free survival was .86.

The active intervention experience was limited to a relatively small sample within a single-site clinic population, which reduces precision and generalizability. Follow-up was only 24 weeks, and the recurrence estimate was imprecise with a wide confidence interval. The trial also evaluated multiple arms, which can complicate interpretation of arm-specific effects.