Adequacy of Vitamin D Replacement in Severe Deficiency Is Dependent on Body Mass Index
Abstract
Background
Obesity is associated with hypovitaminosis D. Whether body mass index (BMI) determines the replacement dose of vitamin D to achieve sufficiency is unclear.
Objective
To determine the relationship between BMI and serum 25-OH vitamin D concentrations and whether the increase in serum 25-OH vitamin D concentrations with vitamin D replacement is dependent on BMI.
Methods
Retrospective review of anthropometric data and serum 25-OH vitamin D concentrations in 95 patients attending an outpatient clinic in a tertiary hospital. In a second component of the study, 17 hospital inpatients with severe vitamin D deficiency (serum 25-OH D concentrations<6 ng/mL [15 nmol/L]) were supplemented with 10,000 units vitamin D3/day orally for 1 week. Biochemistry and anthropometric measurements were compared before and after vitamin D replacement.
Results
Serum 25-OH vitamin D concentrations correlated negatively with BMI in the 95 outpatients (r2=0.11, P <.01). In the longitudinal study, BMI correlated positively with serum intact parathyroid hormone (r2=0.84, P <.01) and negatively with 1.25-(OH)2 vitamin D (r2=0.19, P=.06) at baseline. Serum 25-OH D concentrations achieved following 1 week of vitamin D3 replacement correlated negatively with BMI (r2=0.63, P <.01).
Conclusion
Efficacy of vitamin D supplementation is dependent on BMI. Overweight and obese patients with hypovitaminosis D might require higher doses of vitamin D to achieve vitamin D repletion compared with individuals with normal body weight.
dBone Research Program, ANZAC Research Institute, University of Sydney, New South Wales, Australia
eBone and Mineral Research Program, Garvan Institute of Medical Research, Sydney, New South Wales, Australia
Requests for reprints should be addressed to Paul Lee, MBBS (Hons), Department of Endocrinology, St Vincent's Hospital, 384 Victoria Street, Sydney, New South Wales, Australia 2010
Funding: None.
Conflict of Interest: All authors declare that there are no competing interests to declare.
Authorship: All authors had full access to all of the data in the study and take responsibility for the integrity of the data and the accuracy of the data analysis.
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