Association between body fat and vitamin D status in Korean adults

The relationship between body fat mass and vitamin D appears to vary by ethnicity, but our understanding of this predisposition in Asians is limited due to the scarcity of prior investigations. Data on 1,697 Korean adults were obtained from the second and third years (2008-2009) of the fourth Korean National Health and Nutritional Examination Survey. Body fat mass was measured using dual-energy X-ray absorptiometry. Both linear regression analysis for serum 25-hydroxyvitamin D [25(OH)D] and logistic analysis for vitamin D deficiency [25(OH)D <20 ng/mL] were performed to determine significant predictors among BMI, waist circumference (WC), and body fat percentage (BF), after adjustment of multiple covariates. To explore a possible non-linear relationship between them, the fractional polynomials method was used. All analyses were conducted following stratification by sex. In linear regression analysis, BMI and WC were not associated with 25(OH)D. However, BF was inversely related to 25(OH)D, irrespective of the fat location (both appendicular and truncal fat) in both sexes. In logistic regression analysis, the highest quartile group of BF had a greater OR for vitamin D deficiency than the lower quartile groups, irrespective of the fat location and sex. However, the quartiles of BMI and WC were not associated with vitamin D deficiency. The linear relationships between BF and 25(OH)D (or vitamin D deficiency) were confirmed despite use of the fractional polynomials method. Body fat mass is inversely associated with serum 25(OH)D in Korean adults. Monitoring of vitamin D deficiency in Korean adults with high fat mass is needed.