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Winter youths need at least 1200 IU of vitamin D to maintain 20 nanograms – RCT 2016

Estimation of the dietary requirement for vitamin D in adolescents aged 14-18 years: a dose-response, double-blind, randomized placebo-controlled trial

The American Journal of Clinical Nutrition.
Smith, TJ, Tripkovic, L, Damsgaard,, CT, Mølgaard, C, Ritz, C, Wilson-Barnes, SL, Dowling, KG, Hennessy, A, Cashman, KD, Kiely, M, Lanham-New, SA and Hart, KH

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Background Adolescents are a population group at high risk of low vitamin D status, yet the evidence base for establishing dietary vitamin D requirements to ensure adequacy remains weak.

Objective To establish the distribution of vitamin D intakes required to maintain serum 25- hydroxyvitamin D [25(OH)D] concentrations above proposed cut-offs (25, 30, 40 and 50 nmol/L) during the winter-time in white males and females (14-18 years) in the UK (51o 9 N).

Design In a dose-response trial, 110 adolescents (age 15.9 ± 1.4 years; 43% male) were randomized to receive daily 0, 10 or 20 µg vitamin D3 supplements for 20 weeks during the winter-time. A non-linear regression model was fit to the total vitamin D intake (diet plus supplemental) and post-intervention serum 25(OH)D concentrations, and regression predicted values were used to estimate the vitamin D intakes required to maintain serum 25(OH)D concentrations above specific cut-offs.

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/day 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 post-intervention 25(OH)D concentrations > 25 and > 30 nmol/L in 97.5% of adolescents were estimated as 10.1 and 13.1 µg/day respectively, and 6.6 µg/day to maintain 50% of adolescents > 40 nmol/L. As the response of 25(OH)D plateaued at 46 nmol/L, there is uncertainty in estimating the vitamin D intake required to maintain 25(OH)D > 50 nmol/L in 97.5% of adolescents, but it did exceed 30 µg/day

Conclusions Vitamin D intakes of between 10 and ~30 µg/day are required by white adolescents during the winter-time in order to maintain serum 25(OH)D concentrations > 25 – 50 nmol/L, depending on the serum 25(OH)D threshold chosen.

Vitamin D Council also reported on this study


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