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

Abstract

Vitamin D 2 and D 3 are generally considered equipotent in humans. As Vitamin D 2 supplements are commonly used by elderly in United States, we determined the contribution of 25OHD 2 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 ( P<0.001) was observed between the two methods for the serum total 25OHD measurement. The mean serum 25OHD level in Vitamin D 2 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 D 2 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 D 2 supplements (1.8%) compared to women not taking any supplements (12%).