Estimation of the dietary requirement for vitamin D in healthy adolescent white girls.

BACKGROUND: Knowledge gaps have contributed to considerable variation (between 0 and 15 µg/d) in international dietary recommendations for vitamin D in adolescents. OBJECTIVE: We aimed to establish the distribution of dietary vitamin D required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above several proposed cutoffs (25, 37.5, 40, and 50 nmol/L) during wintertime in adolescent white girls. DESIGN: Data (baseline and 6 mo) from 2 randomized, placebo-controlled, double-blind, 12-mo intervention studies in Danish (55°N) and Finnish (60°N) girls (n = 144; mean age: 11.3 y; mean vitamin D intake: 3.7 µg/d) at vitamin D(3) supplementation amounts of 0, 5, and 10 µg/d were used. Serum 25(OH)D was measured with an HPLC assay in a centralized laboratory. RESULTS: Clear dose-related increments (P < 0.0001) in serum 25(OH)D with increasing supplemental vitamin D(3) were observed. The slope of the relation between vitamin D intake and serum 25(OH)D at the end of winter was 2.43 nmol ⋅ L(-1) ⋅ µg intake(-1), and no difference in the slopes between Finnish and Danish girls was observed. The vitamin D intakes that maintained serum 25(OH)D concentrations at >25, >37.5, and >50 nmol/L in 97.5% of the sample were 8.3, 13.5, and 18.6 µg/d, respectively, whereas an intake of 6.3 µg/d maintained a serum 25(OH)D concentration >40 nmol/L in 50% of the sample. CONCLUSION: The vitamin D intakes required to ensure that adequate vitamin D status [defined variably as serum 25(OH)D >25 and >50 nmol/L] is maintained during winter in the vast majority (>97.5%) of adolescent girls (mean age: 11.3 y) at northern latitudes (>55°N) are 8.3 and 18.6 µg/d, respectively. This trial was registered at clinicaltrials.gov as NCT00267540.