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Heaney, R. P., Davies, K. M., Chen, T. C., Holick, M. F. & Barger-Lux, M. J. (2003) Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. American Journal of Clinical Nutrition, 77 204–210. 
Added by: Sarina (14 Feb 2010 21:32:04 UTC)   
Resource type: Journal Article
BibTeX citation key: Heaney2003a
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Categories: Englisch = English
Keywords: Vitamin D = Vitamin D
Creators: Barger-Lux, Chen, Davies, Heaney, Holick
Collection: American Journal of Clinical Nutrition
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Background: The cholecalciferol inputs required to achieve or maintain any given serum 25-hydroxycholecalciferol concentration are not known, particularly within ranges comparable to the probable physiologic supply of the vitamin.

Objectives: The objectives were to establish the quantitative relation between steady state cholecalciferol input and the resulting serum 25-hydroxycholecalciferol concentration and to estimate the proportion of the daily requirement during winter that is met by cholecalciferol reserves in body tissue stores.

Design: Cholecalciferol was administered daily in controlled oral doses labeled at 0, 25, 125, and 250 µg cholecalciferol for {approx}20 wk during the winter to 67 men living in Omaha (41.2° N latitude). The time course of serum 25-hydroxycholecalciferol concentration was measured at intervals over the course of treatment.

Results: From a mean baseline value of 70.3 nmol/L, equilibrium concentrations of serum 25-hydroxycholecalciferol changed during the winter months in direct proportion to the dose, with a slope of {approx}0.70 nmol/L for each additional 1 µg cholecalciferol input. The calculated oral input required to sustain the serum 25-hydroxycholecalciferol concentration present before the study (ie, in the autumn) was 12.5 µg (500 IU)/d, whereas the total amount from all sources (supplement, food, tissue stores) needed to sustain the starting 25-hydroxycholecalciferol concentration was estimated at {approx}96 µg ({approx}3800 IU)/d. By difference, the tissue stores provided {approx}78–82 µg/d.

Conclusions: Healthy men seem to use 3000–5000 IU cholecalciferol/d, apparently meeting > 80% of their winter cholecalciferol need with cutaneously synthesized accumulations from solar sources during the preceding summer months. Current recommended vitamin D inputs are inadequate to maintain serum 25-hydroxycholecalciferol concentration in the absence of substantial cutaneous production of vitamin D.

Key Words: Vitamin D • cholecalciferol • 25-hydroxycholecalciferol • nutrient requirement • parathyroid hormone • seasonal variation • tolerable upper input level
Added by: Sarina  
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