Vitamin D3 is more potent than vitamin D2

Given its greater potency and lower cost, vitamin D 3 should be the preferred treatment option when correcting vitamin D deficiency, according to a new US study.

In the randomized controlled trial, 35 healthy adults were treated either with 50,000 IU per week (equivalent to 180 micrograms/day) of vitamin D2 or vitamin D3 for 12 weeks (1). To compare the potencies of vitamin D2 and D3 in raising and maintaining vitamin D blood concentrations, the 25(OH)D concentrations in serum and subcutaneous fat were measured in both groups. The results showed that vitamin D3 is approximately 87% more potent in raising and maintaining serum 25(OH)D concentrations and produces 2 to 3-fold greater storage of vitamin D in fat than vitamin D2. When estimating the level of vitamin D3 in total body fat, the stored vitamin amounted to just 17% of the administered dose commonly used by clinicians treating vitamin D deficiency today.

The scientists concluded that vitamin D3 should be regarded as the preferred vitamin D form suitable for treatment, supplementation or fortification. In the past, several studies with different doses and dosing regimens had reported on contradictory potencies of vitamin D3 (cholecalciferol) and vitamin D2 (ergocalciferol) in elevating or sustaining serum 25(OH)D concentrations.

1. Heaney R. P. et al. Vitamin D3 is more potent than vitamin D2 in humans. J Clin Endocrinol Metab. 2011; 96(3).