High-dose vitamin D₃ reduces circulating hepcidin concentrations: A pilot, randomized, double-blind,...

In vitro studies suggest that vitamin D may reduce hepcidin expression and pro-inflammatory cytokine release from monocytes. However, data assessing the vitamin D-mediated effects on iron recycling in healthy individuals are lacking. We aimed to examine the effect of high-dose vitamin D₃ on plasma hepcidin, inflammatory cytokine, and ferritin concentrations in healthy adults.

This was a pilot, double-blind, placebo-controlled trial in healthy adults (N = 28) randomized to receive a one-time oral dose of 250,000 IU of vitamin D₃ or placebo. Between- and within-group differences in plasma hepcidin, pro-inflammatory cytokine [interleukin (IL)-1β, IL-6, IL-8, monocyte chemoattractant protein-1 (MCP-1)], and ferritin concentrations at baseline and 1 week were determined using two-sample and paired t-tests, respectively.

At baseline, plasma 25-hydroxyvitamin D [25(OH)D], hepcidin, pro-inflammatory cytokine, and ferritin concentrations did not differ between the two groups, and greater than 70% of subjects in both groups were vitamin D deficient (25(OH)D < 20 ng/mL). After 1 week, plasma hepcidin concentrations decreased by 73% from baseline in those who received vitamin D₃ (geometric mean ratio [GMR] = 0.27 (95% CI: 0.11-0.62); P = 0.005); there was no significant change in the placebo group (GMR = 0.73 (95% CI: 0.49-1.09); P = 0.11). Plasma cytokine and ferritin concentrations did not change significantly in either group.

High-dose vitamin D₃ significantly reduced plasma hepcidin concentrations in healthy adults 1 week post-dosing, without a change in plasma pro-inflammatory cytokine or ferritin concentrations. These data suggest that vitamin D may have a role in regulating iron recycling by acting independently of changes in pro-inflammatory markers.