25(OH)D status: Effect of D₃ supplement

Excess adipose tissue may lead to sequestrating of vitamin D, making it less available for use in the body.

This study determined if overweight or obese individuals (BMI > 25 kg m^-2) had insufficient (<30 ng mL^-1) levels of 25-hydroxyvitamin D [25(OH)D] and, if so, would serum levels respond to exogenous supplementation.

Sixty-three women who were overweight/obese (BMI = 31.07 ± 5.00 kg m^-2) were randomly assigned in a double-blind manner to receive 5,000 IU of vitamin D₃ (D₃) (n = 31) or a placebo (PL) (n = 32) daily. Serum 25(OH)D concentrations were measured by finger-stick analyses at baseline and after 8 weeks of supplementation. Data were analyzed by using a 2 × 2 (group × time) repeated measure multivariate analysis of variance to determine group differences for pre-values and post-values (p < 0.05).

On day one of the study, both D₃ and PL groups had insufficient levels of vitamin D (mean ± SD) 24.03 ± 9.78 ng mL^-1 and 23.62 ± 9.77 ng mL^-1, respectively. After 8 weeks of supplementation, the D₃ group 25(OH)D level rose to a mean of 43.57 ± 10.87 ng mL^-1 (p < 0.001) versus the PL group whose 25(OH)D level remained statistically unchanged 24.31 ± 8.84 ng mL^-1. Women who were overweight/obese had insufficient vitamin D levels prior to supplementation.

Following supplementation with 5,000 IU of vitamin D₃, all subjects' 25(OH)D levels rose to a sufficient level (≥30 ng mL^-1). The findings of this study concur with the Institute of Medicine and Endocrine Society recommendations in that two to three times the daily requirement of vitamin D is required to improve serum vitamin D levels in individuals who are overweight or obese.