Vitamin D supplementation trial in infancy: body composition effects at 3 years of age in a prospective follow‐up study from Montréal

Summary Background The impact of vitamin D status on body composition is not well understood. Objectives Evaluate how vitamin D supplementation in infancy affects body composition at 3 years of age. Methods Double‐blind randomized trial of 132, 1‐month‐old healthy, breastfed infants randomly assigned to receive oral vitamin D 3 supplements of 400, 800, 1200 or 1600 IU d −1 for 11 months. In the present analysis, 87 (66%) returned at 3 years of age. Body composition was measured using dual‐energy x‐ray absorptiometry and plasma 25‐hydroxyvitamin D [25(OH)D] concentrations by liquid chromatography tandem mass spectrometry. Results Anthropometry, body composition, diet, activity and demographics were similar across dosage groups at 3 years. Mean 25(OH)D concentration from 1 month to 3 years was higher ( P  < 0.001) in the 1200 IU group than 800 and 400 IU groups. Children with 25(OH)D concentrations above 75 nmol L −1 had lower fat mass (~450 g; P  = 0.049). In multiple linear regression, mean 25(OH)D was associated with lean mass percent ( β  = 0.06; CI: 0.00, 0.12; P  = 0.042), fat mass ( β  = −11.29; CI: −22.06, −0.52; P  = 0.048) and body fat percent ( β  = −0.06; CI: −0.12, −0.01; P  = 0.045). Conclusions Higher vitamin D status from infancy through to 3 years of age associates with leaner body composition.