Effect of supplemental vitamin D and calcium on serum sclerostin levels

Objective: Serum sclerostin levels have been reported to be inversely associated with serum 25OHD levels, but the effect of vitamin D and calcium supplementation on serum sclerostin levels is unknown. This study was carried out to determine whether vitamin D and calcium supplementation altered serum sclerostin levels in healthy older adults. Design: We measured serum sclerostin levels at baseline and after 2 years in 279 men and women who participated in a placebo-controlled vitamin D (700 IU/day) and calcium (500 mg/day) intervention trial carried out in men and women aged >= 65 years. Method: Serum sclerostin levels were measured using the MesoScale Discovery chemiluminescence assay. Results: In the men, sclerostin levels increased over 2 years by 4.11+/-1.81 ng/l (13.1%) in the vitamin D plus calcium-supplemented group and decreased by 3.16+/-1.78 ng/l (10.9%) in the placebo group (P=0.005 for difference in change). Adjustments for the season of measurement, baseline physical activity levels, baseline serum sclerostin levels, and total body bone mineral content did not substantially alter the changes. In the women, there was no significant group difference in change in serum sclerostin levels either before or after the above-mentioned adjustments. In both the sexes, vitamin D and calcium supplementation significantly increased serum ionized calcium levels and decreased parathyroid hormone levels. Conclusion: Men and women appear to have different serum sclerostin responses to vitamin D and calcium supplementation. The reason for this difference remains to be determined.