Body size and serum 25 hydroxy vitamin D response to oral supplements in healthy older adults

Background: Vitamin D insufficiency is prevalent in the northeast United States. Since vitamin D insufficiency is readily amenable to supplementation, it is important to understand what factors are associated with serum 25 hydroxy vitamin D (25(OH)D) response to vitamin D supplementation. Objective: In this study we examined the association of serum 25(OH)D response to vitamin D supplementation with body size in a population of elderly subjects. Methods: 257 healthy, ambulatory men and women 65 years of age or older were randomly assigned to treatment with either 700 IU/day (17.5 mu g/d) of supplemental vitamin D-3 and 500 mg/day (12.5 mmol/d) of supplemental calcium, or to placebo. Results: In multivariate regression analyses, after adjusting for baseline 25(OH)D, season, and sex, we found change in 25(OH)D to be inversely associated with baseline BMI (p = 0.01) in subjects treated with supplements for one year. Change in 25(OH)D was also negatively associated with other baseline anthropometric measurements in these subjects. Conclusion: Our study implies that body size should be taken into account when estimating the amount of vitamin D intake needed to raise 25(OH)D to the desired level.