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mardi 12 juin 2012

Vitamine D3: 5 fois plus biodisponible dans les aliments...

La saga de la vitamine D et les erreurs de notre nutrition industrielle associée à une vie sédentaire à l'abri des photons solaires...

Relative effectiveness of oral 25-hydroxyvitamin D3 and vitamin D3 in raising wintertime serum 25-hydroxyvitamin D in older adults1,2,3,4

  1. Tom R Hill
- Author Affiliations
  1. 1From the School of Food and Nutritional Sciences (KDC, KMS, AJL, MK, and TRH) and the Department of Medicine (KDC), University College Cork, Cork, Ireland, and DSM Nutritional Products Ltd, Kaiseraugst, Switzerland (ES and PW).
- Author Notes
  • 2 Supported by the Irish Department of Agriculture, Food and the Marine under its Food Institutional Research Measure (grants to KDC and MK). DSM Nutritional Products Ltd supplied the vitamin D3 and 25-hydroxyvitamin D3 for supplements.
  • 3 Present address for TRH: School of Agriculture, Food and Rural Development and Human Nutrition Research Centre, Newcastle University, Newcastle-Upon-Tyne, United Kingdom.
  • 4 Address correspondence to KD Cashman, School of Food and Nutritional Sciences and Department of Medicine, University College Cork, Cork, Ireland. E-mail: k.cashman@ucc.ie.

Abstract

Background: The relative potency of 25-hydroxyvitamin D3 to vitamin D3 needs to be better defined so that food-composition tables can better reflect the true vitamin D nutritive value of certain foods.
Objective: We performed a randomized, controlled intervention study in apparently healthy, free-living adults to investigate whether the intake of 25-hydroxyvitamin D3 is 5 times more potent in raising serum 25-hydroxyvitamin D [25(OH)D] during winter compared with an equivalent amount of vitamin D3.
Design: A randomized, placebo-controlled, double-blind intervention study was conducted in adults aged ≥50 y (n = 56) who consumed a placebo, 20 μg vitamin D3, or 7 or 20 μg 25-hydroxyvitamin D3 daily throughout 10 wk of winter. Serum 25(OH)D was measured by using an enzyme-linked immunoassay, and serum albumin–corrected calcium (S-Ca) was assessed colorimetrically at the baseline, midpoint, and endpoint of the study.
Results: The mean (±SD) increases (per microgram of vitamin D compound) in serum 25(OH)D concentrations over baseline after 10 wk of supplementation were 0.96 ± 0.62, 4.02 ± 1.27, and 4.77 ± 1.04 nmol · L−1 · μg intake−1 for the 20-μg vitamin D3/d and 7- and 20-μg 25-hydroxyvitamin D3/d groups, respectively. A comparison of the 7- and 20-μg 25-hydroxyvitamin D3/d groups with the 20-μg vitamin D3/d group yielded conversion factors of 4.2 and 5, respectively. There was no effect of treatment on S-Ca concentrations and no incidence of hypercalcemia (S-Ca >2.6 nmol/L).
Conclusions: Each microgram of orally consumed 25-hydroxyvitamin D3 was about 5 times more effective in raising serum 25(OH)D in older adults in winter than an equivalent amount of vitamin D3. This conversion factor could be used in food-compositional tables for relevant foods. This study was registered at clinicaltrials.gov as NCT01398202.

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