Vitamin D₂ vs. Vitamin D₃ Supplementation — Does It Matter?

Supplemental vitamin D is available as either D₂ (ergocalciferol) or D₃ (cholecalciferol), but a few studies have suggested that D₂ maintains serum levels of 25-hydroxyvitamin D less effectively than does D₃. In this double-blind randomized study from Boston, 68 healthy adults received daily doses of vitamin D₂ (1000 IU), vitamin D₃ (1000 IU), a combination of D₂ plus D₃ (500 IU each), or placebo. Supplements were given for 11 weeks at the end of winter.

At baseline, total serum 25-hydroxyvitamin D levels averaged about 19 ng/mL. At 11 weeks, mean levels had increased significantly (by about 9 ng/mL) in all three active treatment groups, without significant differences between groups. The mean level did not change in the placebo group.