Dose response to vitamin D supplementation among postmenopausal African American women

Background: Reports on the dose response to vitamin D are conflicting, and most data were derived from white men and women. Objective: The objective was to determine the response of serum 25-hydroxyvitamin D [25(OH)D] to oral vitamin D, supplementation in an African American population. Design: Healthy black postmenopausal women (n = 208) participated in a vitamin D, supplementation trial for a period of 3 y. Analyses were done in the vitamin D supplementation arm (n = 104) to quantify the response in serum 25-hydroxyvitamin D concentrations at a steady state vitamin D input. The participants received 20 mu g/d (800 IU) oral vitamin D-3 for the initial 2 y and 50 mu g/d (2000 IU) for the third year. Results: Supplementation with 20 mu g/d (800 IU/d) vitamin D3 raised the mean serum 25(OH)D concentration from a baseline of 46.9 +/- 20.6 nmol/L to 71.4 +/- 21.5 nmol/L at 3 mo. The mean (+/- SD) concentration of serum 25(OH)D was 87.3 +/- 27.0 nmol/L 3 mo after supplementation increased to 50 fLgld (2000 IU/d). All participants achieved a serum 25(OH)D concentration > 35 nmol/L, 95% achieved a concentration > 50 nmol/L, but only 60% achieved a concentration > 75 nmol/L. All patients had concentrations < 153 nmol/L. On the basis of our findings, an algorithm for prescribing vitamin D so that patients reach optimal serum concentrations was developed. The algorithm suggests a dose of 70 mu g (2800 IU/d) for those with a concentration > 45 nmol/L and a dose of 100 mu g (4000 IU/d) for those with a concentration < 45 nmol/L. Conclusions: Supplementation with 50 mu g/d (2000 IU/d) oral vitamin D, is sufficient to raise serum 25-hydroxyvitamin D concentrations to > 50 nmol/L in almost all postmenopausal African American women. However, higher doses were needed to achieve concentrations > 75 nmol/L in many women in this population.