Miriam Blum, MD, Gerard E. Dallal, PhD, and Bess Dawson-Hughes, MD
Bone Metabolism Laboratory (M.B., B.D.H.) and Biostatistics Department (G.E.D.), Jean Mayer U. S. Department of Agriculture Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts
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 /ng/d) of supplemental vitamin D3 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.
Mean adjusted change in 25(OH)D level (±SEM) at one year in the calcium-vitamin D and placebo groups, each divided into subgroups based on BMI at baseline.
- SubgroupI: BMI < 25 kg/m2,
- subgroup II: 25 kg/m2 < BMI < 30 kg/m2,
- subgroup III: BMI 2=30 kg/m2).
Mean change in 25(OH)D level for calcium-vitamin D BMI subgroups (ANOVA P = 0.05) and placebo BMI subgroups (NS) are each adjusted for baseline 25(OH)D level and season. Sample size for the six groups from left to right are as follows: n = 47, n = 46, n = 59, n = 56, n = 26, n = 23. *Significantly differs from BMI subgroup I (P < 0.05). To convert values for serum 25(OH)D to nmol/l, multiply by 2.5.
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