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Association of Plasma Vitamin D Levels with Adiposity in Hispanic and African Americans

Colorado School of Public Health (K.A.Y., J.M.N.), University of Colorado Denver, Aurora, Colorado 80045; Department of Population Health Sciences (C.D.E.), University of Wisconsin School of Medicine and Public Health, Madison, Wisconsin 53706; Department of Public Health Sciences (C.D.L., K.G.H.), Wake Forest University School of Medicine, Winston-Salem, North Carolina 27157; Division of Clinical Epidemiology (S.M.H.), University of Texas Health Sciences Center, San Antonio, Texas 78229; and Harold Hamm Diabetes Center (M.B.-A.), University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma 73104

Address all correspondence and requests for reprints to: Jill M. Norris, M.P.H., Ph.D., Colorado School of Public Health, 13001 East 17th Place, Box B119, Aurora, Colorado 80045. E-mail: jill.norris{at}ucdenver.edu.

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.