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  • Title: Vitamin D supplementation during Antarctic winter.
    Author: Smith SM, Gardner KK, Locke J, Zwart SR.
    Journal: Am J Clin Nutr; 2009 Apr; 89(4):1092-8. PubMed ID: 19225122.
    Abstract:
    BACKGROUND: Persons with limited exposure to ultraviolet B light, including space travelers, may not receive enough vitamin D. Recent studies indicate that optimal serum 25-hydroxyvitamin D [25(OH)D] should be > or = 80 nmol/L. OBJECTIVE: This study was designed to evaluate the effectiveness of 3 doses of vitamin D to raise and maintain 25(OH)D to a concentration >80 nmol/L in persons with limited ultraviolet B light exposure. DESIGN: This was a 5-mo, prospective, randomized, double-blind study of vitamin D supplementation. It was conducted during winter in Antarctica at the McMurdo Station, when ultraviolet B radiation levels are essentially zero. The 55 subjects were randomly divided into 3 groups for vitamin D supplementation: 2000 IU/d (n = 18), 1000 IU/d (n = 19), and 400 IU/d (n = 18). An additional 7 subjects did not take supplements or took supplements of their own choosing. Blood samples were collected about every 2 mo during the winter. RESULTS: About 5 mo after supplementation started, 25(OH)D increased to 71 +/- 23 nmol/L in the 2000-IU/d group, 63 +/- 25 nmol/L in the 1000-IU/d group, and 57 +/- 15 nmol/L in the 400-IU/d group and decreased to 34 +/- 12 nmol/L in the group not taking supplements. CONCLUSIONS: These data will enable us to provide space crews with evidence-based recommendations for vitamin D supplementation. The findings also have implications for other persons with limited ultraviolet light exposure, including polar workers and the elderly.
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