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

Abstract

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 microg/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.

Figures

Figure 1

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. (Subgroup I: BMI 2, subgroup II: 25 kg/m2 ≤ BMI< 30 kg/m2, subgroup III: BMI ≥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.