Estimation of the dietary requirement for vitamin D in healthy adolescent white girls.
Am J Clin Nutr. 2011 Jan 26.
Cashman KD, Fitzgerald AP, Viljakainen HT, Jakobsen J, Michaelsen KF, Lamberg-Allardt C, Mølgaard C.
School of Food and Nutritional Sciences and Departments of Medicine and Epidemiology and Public Health, and Statistics, University College Cork, Cork, Ireland.
BACKGROUND: Knowledge gaps have contributed to considerable variation (between 0 and 15 ?g/d) between 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 ?g/d) at vitamin D(3) supplementation amounts of 0, 5, and 10 ?g/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) ? ?g 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 ?g/d, respectively, whereas an intake of 6.3 ?g/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 ?g/d, respectively. This trial was registered at clinicaltrials.gov as NCT00267540. PMID: 21270380
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To get >10 ng/ml need 332 IU,
To get >20 ng/ml need 744 IU - to prevent Rickets, but not much else