Estimation of the dietary requirement for vitamin D in adolescents aged 14-18 y: a dose-response, double-blind, randomized placebo-controlled trial.
What this study found
Vitamin D3 increased serum 25(OH)D concentrations in both active arms, while calcium and PTH were essentially unchanged. In the 10 mg/day group, mean 25(OH)D rose from 49.2 6 12.0 to 56.6 6 12.4 nmol/L, with a total change of 6.7 6 9.9 nmol/L; in the 20 mg/day group, it rose from 51.7 6 13.4 to 63.9 6 10.6 nmol/L, with a total change of 12.1 6 10.6 nmol/L. Between-group differences at the end of the trial were significant, P < 0.001. The trial supports vitamin D supplementation as effective for raising winter 25(OH)D in adolescents, with higher intakes producing larger increases.
- Study & population
- Double-blind, randomized, placebo-controlled dose-response trial conducted during winter in healthy white adolescents aged 14 to 18 years in the United Kingdom.
- Intervention
- Oral vitamin D3 tablets were given daily for 20 weeks at two active doses: 10 mg/day and 20 mg/day.
- Key limitation
- Active-arm sample sizes were modest, and the study population was limited to healthy white UK adolescents studied in winter, which narrows generalizability.
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Open PDFOriginal abstract
BACKGROUND Adolescents are a population group at high risk of low vitamin D status, yet the evidence base for establishing dietary vitamin D requirements remains weak. OBJECTIVE The aim was to establish the distribution of vitamin D intakes required to maintain serum 25-hydroxyvitamin D [25(OH)D] concentrations above proposed cutoffs (25, 30, 40, and 50 nmol/L) during winter in white males and females (14-18 y of age) in the United Kingdom (51°N). DESIGN In a dose-response trial, 110 adolescents (aged 15.9 ± 1.4 y; 43% males) were randomly assigned to receive 0, 10, or 20 μg vitamin D3 supplements/d for 20 wk during winter. A nonlinear regression model was fit to total vitamin D intake and postintervention serum 25(OH)D concentrations, and regression-predicted values estimated the vitamin D intakes required to maintain serum 25(OH)D concentrations above specific cutoffs. RESULTS Mean ± SD serum 25(OH)D concentrations increased from 49.2 ± 12.0 to 56.6 ± 12.4 nmol/L and from 51.7 ± 13.4 to 63.9 ± 10.6 nmol/L in the 10- and 20-μg/d groups, respectively, and decreased in the placebo group from 46.8 ± 11.4 to 30.7 ± 8.6 nmol/L (all P ≤ 0.001). Vitamin D intakes required to maintain 25(OH)D concentrations >25 and >30 nmol/L in 97.5% of adolescents were estimated to be 10.1 and 13.1 μg/d, respectively, and 6.6 μg/d to maintain 50% of adolescents at concentrations >40 nmol/L. Because the response of 25(OH)D reached a plateau at 46 nmol/L, there is uncertainty in estimating the vitamin D intake required to maintain 25(OH)D concentrations >50 nmol/L in 97.5% of adolescents, but it exceeded 30 μg/d. CONCLUSION Vitamin D intakes between 10 and ∼30 μg/d are required by white adolescents during winter to maintain serum 25(OH)D concentrations >25-50 nmol/L, depending on the serum 25(OH)D threshold chosen. This trial was registered at clinicaltrials.gov as NCT02150122 and as International Standard Randomized Controlled Trial Number ISRCTN40736890.