Decreased serum levels of 1,25-(OH)(2)vitamin D during 1 year of sunlight deprivation in the Antarctic

French Antarctic territories harbor bases that are devoted to scientific an d technical work. Living and working conditions during 1-year sojourns in s uch an environment are quite acceptable, but the confinement and the drop i n ultraviolet B radiation exposure during winter months raise the problem o f preservation of normal vitamin D status. Seasonal variations in 25-hydrox yvitamin D [25(OH)D] levels have been well documented, but the effect of su nshine deprivation on 1,25 dihydroxyvitamin D [1,25(OH)(2)D] levels is quit e controversial. The aim of this study was to address this question under t he exceptional conditions of lack of sunshine exposure. Fifteen male Caucas ian subjects participating in a 1-year mission in Antarctica were investiga ted. They were subjected to seven blood samplings, one before and six durin g their sojourn. Serum levels of 25(OH)D, 1,25(OH)(2)D, osteocalcin, and IC TP were measured. We found that levels of 25(OH)D and 1,25(OH)(2)D signific antly decreased in these subjects during the mission, minimum levels being observed 10 months after their departure from France. ICTP concentrations d id not change throughout this study, but osteocalcin levels were found to b e higher at the end of the sojourn than before departure, which could argue for the existence of bone remodeling changes. Further studies are now need ed to fully investigate bone metabolism changes and to address the question of vitamin D supplementation during this kind of sojourn.