Vitamin D Status and Response to Vitamin D3 in Obese vs. Non‐obese African American Children

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Abstract
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 D3 daily for 1 month. Serum 25(OH)D, 1,25‐dihydroxyvitamin D (1,25(OH)2D), 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 ≤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 D3 (2× the recommended adequate intake) daily for 1 month was inadequate to raise their blood levels of 25(OH)D to ≥30 ng/ml.