Dose response to vitamin D supplementation among postmenopausal African American women

Researchers from the Bone Mineral Research Center in Winthrop University Hospital in Mineola, NY wanted to determine the response of serum 25-hydroxyvitamin D [25(OH)D] to oral vitamin D3 supplementation in an African American population because the reports on the dose response to vitamin D were derived from white men and women.

208 healthy black postmenopausal women participated for a period of 3 y. The participants received 800 IU per day of oral vitamin D3 for the initial 2 years and 2000 IU for the third year. Supplementation with 800 IU a day of vitamin D3 raised the mean serum 25(OH)D concentration from a baseline of 46.9 nmol/L to 71.4 3 mo. The mean concentration of serum 25(OH)D was 87.3 nmol/L 3 mo after supplementation increased to 2000 IU per day. All participants achieved a serum 25(OH)D concentration greater than 35 nmol/L. 95% achieved a concentration greater than 50 nmol/L, but only 60% achieved a concentration greater than 75 nmol/L.

On the basis of these findings, an algorithm for prescribing vitamin D so that patients reach optimal serum concentrations was developed. The algorithm suggests a dose of 2800 IU per day for those with a concentration initially greater than 45 nmol/L and a dose of 4000 IU/d for those with a concentration initially less than 45 nmol/L. Conclusions: Supplementation with 2000 IU per day of oral vitamin D3 is sufficient to raise serum 25-hydroxyvitamin D concentrations to greater than 50 nmol/L in almost all postmenopausal African American women. However, higher doses were needed to achieve concentrations greater than 75 nmol/L in many women in this population. The study is published in the December 2007 issue of the American Journal of Clinical Nutrition.