New research from Norway reports that supplements containing vitamin D3 can increase blood concentrations more effectively than the D2 form.
The randomized controlled trial tested the effects of a daily supplementation with 50 micrograms (2,000 IU) of vitamin D2 (ergocalciferol) or D3 (cholecalciferol) or a placebo for 8 weeks on serum 25(OH)D2 and 25(OH)D3 concentrations in 107 healthy participants (1). The study was conducted at latitude of 51°47N during winter, when UVB radiation is virtually absent. The results showed that at the beginning of the study the aver-age total 25(OH)D concentration was 40.2 nmol/L, indicating that suboptimal vitamin D status was prevalent among the participants. Over the 8 weeks, total levels of 25(OH)D rose significantly in both supplementation groups, but fell in the placebo group. The greatest increases of total 25(OH)D were measured for those participants taking vitamin D3 supplements (41.5 nmol/L to 88 nmol/L). In the group receiving vitamin D2, the 25(OH)D2 concentrations increased significantly, while the 25(OH)D3 concentration fell significantly (36.4 nmol/L to 16.6 nmol/L) after the 8 weeks.
The researchers concluded that vitamin D3 supplementation can increase the total vitamin D concentration to a greater degree than vitamin D2 supplementation can. Thus, vitamin D3 should be used for supplementation and fortification purposes. The underlying reason for this difference seems to be a substantial decrease in 25(OH)D3 in people taking vitamin D2. The related biological mechanism remains to be elucidated. It is impor-tant to know which form is more effective, given the widespread problem of vitamin D deficiency, the scientists said.
It has long been debated whether the two supplement forms of vitamin D are bioequivalent. Some studies have suggested that vitamin D2 (the type commonly found in plants, mainly mushrooms) is less biologically active than vitamin D3, which is found in animals and produced in human skin.