Selective monitoring of vitamin D2 and D3 supplementation with a highly specific 25-hydroxyvitamin D3 immunoassay with negligible cross-reactivity to 25-hydroxyvitamin D2

Background: The effects of vitamin D-2 and D-3 supplementation on circulating concentrations of 25(OH)D-3 require reliable analytical tools for specific determination of 25(OH)D-3 and 25(OH)D-2. We have developed a highly specific 25-OH Vitamin D3 ELISA with negligible cross-reactivity towards 25(OH)D-2. Methods: 25(OH)D-3 concentrations were measured in several study participants: 1) 641 healthy men and women; 2) 39 postmenopausal women receiving 400-800 IU vitamin D-3 daily for 4 months; 3) 45 men and women with hip fracture receiving 1000 IU vitamin D-2 daily for 3 months. Results: This 25-OH Vitamin D3 ELISA had minimal cross-reactivity to 25(OH)D-2, (0.7%), and demonstrated a high correlation (r(2)=0.93) with 25(OH)D-3 determined by HPLC. 25(OH)D-3 increased by 14% in subjects receiving vitamin D-3 for 4 months (p<0.01), whereas there was no significant change in 25(OH)D-3 levels in those receiving vitamin D-2. Conclusions: We report that 25(OH)D-3 ELISA was used for evaluation of 25(OH)D-3 concentrations in subjects receiving vitamin D-2 and D-3 Supplementation. The increase of 25(OH)D-3 in circulation with vitamin D3 supplementation and lack of increase with vitamin D-2 supplementation suggest that this assay has sufficient sensitivity and specificity to be used as a reliable measurement of nutritional vitamin D-3 Status in humans. (C) 2009 Elsevier B.V. All rights reserved.