Original Article
Ruban Dhaliwal, MD; Mageda Mikhail, MD; Martin Feuerman, MS; John F. Aloia, MD
ABSTRACT Objective: The prevalence of vitamin D inadequacy is high in obese individuals. Determining the response of serum 25-hydroxyvitamin D (25[OH]D) to vitamin D3 supplementation in obese and nonobese individuals may lead to concurrent recommendations for optimal vitamin D intake in these populations. The objective of this study was to determine the dose response of vitamin D3 in subjects with a body mass index ≥35 kg/m². Methods: Randomized, double-blind, placebo-controlled study. This study is an extension of our previous study of vitamin D dosing in healthy adults. After an assessment of baseline 25(OH)D levels, participants were randomized to a vitamin D supplementation arm (100 µg daily if baseline 25[OH]D was 50 nmol/L in 97.5% of women (10). Dose response is complicated by the fact that vitamin D metabolism is affected by sun exposure (11), skin color (12,13), and body mass index (BMI) (14). Some authors have shown that the dose response depends on the basal 25(OH)D levels, but the results are inconsistent (15-18). Vitamin D is stored in the adipose tissue and adiposity has significant implications for its bioavailability. Hence, obesity is considered a risk factor for vitamin D deficiency. Bell et al (19) reported significant differences in vitamin D metabolism between obese and nonobese individuals, with significantly lower 25(OH)D and higher parathyroid hormone and 1,25-dihydroxyvitamin D (1,25[OH]D) levels in obese compared to nonobese white subjects. Hypponen et al (20) also investigated the prevalence of hypovitaminosis D in a white British population and found that obese individuals were twice as likely to have vitamin D3 levels
Ruban Dhaliwal, MD; Mageda Mikhail, MD; Martin Feuerman, MS; John F. Aloia, MD
ABSTRACT Objective: The prevalence of vitamin D inadequacy is high in obese individuals. Determining the response of serum 25-hydroxyvitamin D (25[OH]D) to vitamin D3 supplementation in obese and nonobese individuals may lead to concurrent recommendations for optimal vitamin D intake in these populations. The objective of this study was to determine the dose response of vitamin D3 in subjects with a body mass index ≥35 kg/m². Methods: Randomized, double-blind, placebo-controlled study. This study is an extension of our previous study of vitamin D dosing in healthy adults. After an assessment of baseline 25(OH)D levels, participants were randomized to a vitamin D supplementation arm (100 µg daily if baseline 25[OH]D was 50 nmol/L in 97.5% of women (10). Dose response is complicated by the fact that vitamin D metabolism is affected by sun exposure (11), skin color (12,13), and body mass index (BMI) (14). Some authors have shown that the dose response depends on the basal 25(OH)D levels, but the results are inconsistent (15-18). Vitamin D is stored in the adipose tissue and adiposity has significant implications for its bioavailability. Hence, obesity is considered a risk factor for vitamin D deficiency. Bell et al (19) reported significant differences in vitamin D metabolism between obese and nonobese individuals, with significantly lower 25(OH)D and higher parathyroid hormone and 1,25-dihydroxyvitamin D (1,25[OH]D) levels in obese compared to nonobese white subjects. Hypponen et al (20) also investigated the prevalence of hypovitaminosis D in a white British population and found that obese individuals were twice as likely to have vitamin D3 levels
