In the Journal Clinical Endocrinology Metabolism

2004;89:5387-5391.

Armas LAG, et al. found that

"Vitamin D2 is much less effective than vitamin D3 in humans."

Twenty healthy male volunteers were randomly assigned to receive a single 50,000-IU dose of either vitamin D2 (ergocalciferol) or vitamin D3 (cholecalciferol)...They found that the potency of vitamin D2 being only 10.6% that of vitamin D3.

That means 100 IU of D3 is equivalent to 1000 IU of D2. Make sure that your multi-vitamin contains D3 not D2.

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