Scott M Smith 2008

Vitamin D supplementation during Antarctic winter

 * Scott M Smith, Keri K Gardner, James Locke, Sara R Zwart
 * Randomized Controlled Trial
 * American Journal of Clinical Nutrition, 89(4):1092-8.
 * doi: 10.3945/ajcn.2008.27189
 * PMID: 19225122
 * https://pubmed.ncbi.nlm.nih.gov/19225122/
 * 2009 Apr

Arctic workers were dosed with Vitamin-D. At the highest dose more than half of the subjects did not achieve the minimum required serum levels, all others were even worse off.

"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 >= 80nmol/l (32ng/ml)."

"About 5 months after supplementation started, 25(OH)D increased to 71 +/- 23nmol/l (28.4 +/- 9.2ng/ml) in the 50ug/d (2000-IU/d) group"