Association of plasma vitamin D levels with adiposity in hispanic and African Americans

Abstract

Context: Previous studies have suggested vitamin D insufficiency is associated with increased obesity; however, the relationship between 25-hydroxyvitamin D (25[OH]D) and 1,25-dihydroxyvitamin D (1,25[OH] 2D) and measures of adiposity has not been well characterized in minority populations. Objective: The objective of the study was to examine the relationship between levels of 25[OH]D and 1,25[OH]2D and measures of adiposity in Hispanic and African-Americans at baseline and on change in these measures over time. Design and Setting: The Insulin Resistance Atherosclerosis (IRAS) Family Study examined 917 Hispanics and 439 African-Americans at baseline and again 5.3 yr later (n = 1081 at follow-up). Main Outcome Measure: 25[OH]D (nanograms per milliliter) and 1,25[OH]2D (picograms per milliliter) were measured at baseline. Abdominal sc adipose tissue (SAT), visceral adipose tissue (VAT; both determined by computed tomography scan), and body mass index (BMI) were measured at baseline and follow-up. Results: 25[OH]D was inversely associated with BMI, VAT, and SAT in both populations at baseline (P<0.001). 25[OH]D was marginally inversely associated with baseline visceral fat to sc fat ratio in African-Americans (P=0.049) but not Hispanics. 1,25[OH]2D was inversely associated with BMI (P<0.0001, P=0.002) and VAT (P = 0.0005, P = 0.012) in Hispanics and African-Americans, respectively, whereas 1,25[OH] 2D was inversely associated with SAT in Hispanics (P<0.0001) and with visceral fat to sc fat ratio in African-Americans (P = 0.02). Adjusting for 25[OH]D attenuated these associations; 1,25[OH]2D remained associated with BMI in both populations (P < 0.05) and with SAT (P = 0.004) in Hispanics. No significant associations between 5-yr change in adiposity and 25[OH]D or 1,25[OH]2D were seen. Conclusions: Vitamin D levels were inversely associated with baseline BMI, SAT, and VAT in Hispanic and African-Americans but were not associated with 5-yr change in adiposity. Copyright © 2009 by The Endocrine Society.