Effect of Vitamin D supplement use on serum concentrations of total 25OHD levels in elderly women

Vitamin D₂ and D₃ are generally considered equipotent in humans. As Vitamin D₂ supplements are commonly used by elderly in United States, we determined the contribution of 25OHD₂ to the total serum 25OHD levels by HPLC in elderly women who reported taking Vitamin D ₂ supplements (n=56) and also in a group of randomly selected unsupplemented women (n=60). In addition, we compared the total serum 25OHD measured by HPLC with competitive protein-binding assay (CPBA), a method routinely employed to measure Vitamin D status. A correlation of 0.91 (P2 supplemented group was significantly higher than in unsupplemented group measured by HPLC (32 versus 28 ng/ml) and marginally higher measured by CPBA (33 vs. 31 ng/ml). Seventy eight percent of women taking Vitamin D₂ supplements had appreciable amounts of circulating 25OHD_2, which constituted about 25 percent of their total serum 25OHD. It is also interesting to note that Vitamin D deficiency was less prevalent in elderly women taking Vitamin D₂ supplements (1.8%) compared to women not taking any supplements (12%).