Research Supports Potency of Vitamin D3

Vitamin D3 is more potent than vitamin D2, according to a recent study. Previous research has been conflicting as to whether the two forms of vitamin D (calciferols) had equal biological activity. Vitamin D2 (ergocalciferol) is formed by plants upon exposure to sunlight. However, humans synthesize vitamin D3 (cholecalciferol) in the skin upon UV light exposure. Vitamin D3 is converted in the liver to 25-hydroxycholecalciferol, which is then converted to the biologically active form, 1,25-dihydroxycholecalciferol, in the kidney.

In this new single-blind, randomized study, 33 subjects received 50,000 IU per week of either vitamin D2 or vitamin D3. After 12 weeks, the subjects were evaluated for serum 25-hydroxyvitamin D, which is the primary circulating form of vitamin D in the body. The subjects were also evaluated for calciferol content in subcutaneous fat.

The results of the study showed that the mean 25-hydroxyvitamin D levels were higher in the group receiving the vitamin D3 compared to the group receiving vitamin D2. Additionally, subcutaneous levels of mean calciferol were higher in the vitamin D3 group compared to the vitamin D2 group. More specifically, the vitamin D2 group showed an increase in vitamin D2 in the subcutaneous fat by 50 mcg/kg, whereas the vitamin D3 group showed an increase in vitamin D3 by 104 mcg/kg. Furthermore, total calciferol levels in subcutaneous fat increased by 33 mcg/kg in the vitamin D2 group, compared to 104 mcg/kg in the vitamin D3 group.

The researchers concluded, “D3 is approximately 87 percent more potent in raising and maintaining serum 25-hydroxyvitamin D concentrations and produces 2- to 3-fold greater storage of vitamin D than does equimolar D2. For neither was there evidence of sequestration in fat, as had been postulated for doses in this range. Given its greater potency and lower cost, D3 should be the preferred treatment option when correcting vitamin D deficiency.”

Reference:

Heaney RP, Recker RR, Grote J, Horst RL, Armas LA. Vitamin D3 Is More Potent Than Vitamin D2 in Humans. J Clin Endocrinol Metab. 2010 Dec 22. Published Online Ahead of Print.