Obesity Types in Vitamin D-Deficient Children Vary with Race

Lead author Silva A. Arslanian, MD, from the University of Pittsburgh School of Medicine in Pittsburg, Pennsylvania, stated that, "Vitamin D deficiency is rampant in American youth, and there is some suggestion in adults that low levels of vitamin D may be playing a role in the increasing rates of Type 2 diabetes." "It is possible the same may be true for youth with Type 2 diabetes." "Our study found that vitamin D was associated with higher fat levels and lower levels of high-density lipoprotein (HDL), also known as good cholesterol, in both black and white children." 

The goal of the study was to evaluate the association between vitamin D status, total and abdominal adiposity, and lipids in black and white children. Healthy obese and nonobese black and white children (n = 237) 8 to 18 years old underwent measurement of plasma 25-hydroxyvitamin D (25[OH]D) levels, adiposity (body mass index [BMI], percentage of total body fat, visceral adipose tissue [VAT], and subcutaneous adipose tissue [SAT]), and fasting lipids. Mean age was 12.7 ± 2.2 years; 47% were black, 47% were obese, and 43% were boys.

For the entire cohort, mean 25(OH)D concentration was 19.4 ± 7.4 ng/mL. Vitamin D deficiency, defined as a 25(OH)D level of less than 20 ng/mL, was present in 40% of the white children and in 73% of the black children. In the overall cohort, there was an inverse association of plasma 25(OH)D level with BMI, BMI percentile, percentage of total body fat, VAT, and SAT, and a positive association with HDL cholesterol level. Compared with their respective vitamin D-nondeficient counterparts, vitamin D-deficient whites had higher VAT, whereas vitamin D-deficient blacks had higher SAT.

Independent significant predictors of 25(OH)D status were race, season, pubertal status, and VAT. The odds for vitamin D deficiency was higher for black vs. white race (odds ratio [OR], 6.00; P < .001), female vs. male sex (OR, 2.01; P = .023), prepubertal vs. pubertal children (OR, 2.88; P = .012), and winter/spring vs. summer/fall season (OR, 2.29; P = .010). Also, each 10-cm² increase in VAT increased the OR for vitamin D deficiency by 1.087 (P = .042).

"In black and white youth examined together, lower levels of 25(OH)D are associated with higher adiposity measures and lower HDL," the study authors write. "Further, vitamin D deficiency is associated with higher VAT in whites and greater SAT in blacks."

Limitations of this study include lack of data on recognized confounders of vitamin D status, including dietary vitamin D, duration of sun exposure, usage of sunscreen, quantification of UV radiation, and objective assessment of skin melanization with a skin spectrophotometer. In addition, there were a small number of non-vitamin D-deficient black children, with associated limited variability in BMI categories in this group.

Arslanian said, "Besides therapeutic interventions to correct the high rates of vitamin D deficiency in youth, benefits of vitamin D optimization on fat levels, lipid profile and risk of Type 2 diabetes need to be explored."

J Clin Endocrinol Metab. 2011;96:1560-1567.