Vitamin D supplementation during Antarctic winter

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 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 con-centration.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 choos-ing. Blood samples were collected about every 2 mo during the winter. Results: About 5 mo after supplementation started, 25(OH)D increased to 71 6 23 nmol/L in the 2000-IU/d group, 63 6 25 nmol/L in the 1000-IU/d group, and 57 6 15 nmol/L in the 400-IU/d group and decreased to 34 6 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 supplemen-tation. The findings also have implications for other persons with limited ultraviolet light exposure, including polar workers and the elderly. Am J Clin Nutr 2009;89:1092–8