Differences in the absorption and metabolism of vitamin D2, vitamin D3, and 25 hydroxyvitamin D

A challenge for public health is to make recommendations for the intake of vitamin D to optimize health and prevent disease. Vitamin D supplementation can be accomplished using vitamin D2 (from fungi), vitamin D3 (from vertebrate sources), or as the prehormone 25 hydroxyvitamin D3 (25OHD3). While these three sources are generally effective for raising and maintaining vitamin D status, their effect is not identical. This review will summarize the differences between these molecules in their routes of absorption, their metabolism, degradation, and molecular function.