Background: Serum 25-hydroxyvitamin D (25(OH)D) is low in obese adults.
Objective: To examine serum 25(OH)D in obese (BMI >95th percentile for age) vs. non-obese (BMI = 5th-75th percentile for age) 6-10-year-old African American children and compare their differences in therapeutic response to vitamin D supplementation.
Methods and procedures: In an open label non-randomized pre-post comparison 21 obese (OB) and 20 non-obese (non-OB) subjects matched for age, sex, skin color, and pubertal maturation were treated with 400 IU of vitamin D(3) daily for 1 month. Serum 25(OH)D, 1,25-dihydroxyvitamin D (1,25(OH)(2)D), parathyroid hormone (PTH), leptin, and markers of bone turnover (serum bone-specific alkaline phosphatase (BSAP), osteocalcin (OC), and urine n -telopeptide cross-links of type 1 collagen (urine NTX)) were measured. Vitamin D deficiency was defined as serum 25(OH)D < or =20 ng/ml and insufficiency as 21-29 ng/ml respectively.
Results: Vitamin D deficiency occurred in 12/21 (57%) OB vs. 8/20 (40%) non-OB at baseline (P = 0.35) and persisted in 5/21 (24%) OB vs. 2/18 (11%) non-OB (P = 0.42) after treatment. When the cohort was stratified by the baseline levels of 25(OH)D, there were differences in the response to treatment in the obese and non-obese cohorts.
Discussion: Vitamin D deficiency was common among OB and non-OB preadolescent African American children, and 400 IU of vitamin D(3) (2x the recommended adequate intake) daily for 1 month was inadequate to raise their blood levels of 25(OH)D to > or =30 ng/ml.