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

Abstract

French Antarctic territories harbor bases that are devoted to scientific and technical work. Living and working conditions during 1-year sojourns in such an environment are quite acceptable, but the confinement and the drop in ultraviolet B radiation exposure during winter months raise the problem of preservation of normal vitamin D status. Seasonal variations in 25-hydroxyvitamin D [25(OH)D] levels have been well documented, but the effect of sunshine deprivation on 1,25 dihydroxyvitamin D [1,25(OH)2D] levels is quite controversial. The aim of this study was to address this question under the exceptional conditions of lack of sunshine exposure. Fifteen male Caucasian subjects participating in a 1-year mission in Antarctica were investigated. They were subjected to seven blood samplings, one before and six during their sojourn. Serum levels of 25(OH)D, 1,25(OH)2D, osteocalcin, and ICTP were measured. We found that levels of 25(OH)D and 1,25(OH)2D significantly decreased in these subjects during the mission, minimum levels being observed 10 months after their departure from France. ICTP concentrations did not change throughout this study, but osteocalcin levels were found to be higher at the end of the sojourn than before departure, which could argue for the existence of bone remodeling changes. Further studies are now needed to fully investigate bone metabolism changes and to address the question of vitamin D supplementation during this kind of sojourn.

Vitamin D supplementation during Antarctic winter

“…As in other studies conducted in Antarctica, bone-specific alkaline phosphatase increased over time, which indicated that bone formation may have increased (23,24). It is possible that 1,25-dihydroxyvitamin D and calcium increased in response to a feedback mechanism to maintain available calcium when bone remodeling increased, as evidenced by the increase in bone-specific alkaline phosphatase.…”

Serum 25-Hydroxyvitamin D Is a Predictor of Serum 1,25-Dihydroxyvitamin D in Overweight and Obese Patients,

“…Furthermore, a temporary 1-y sunlight deprivation under Antarctic conditions resulted in a significant decrease of 25(OH)D and 1,25(OH) 2 D levels in 15 healthy adult men, with the lowest levels being observed after 10 mo from departure from southern latitudes (35). This probably indicates that serum 1,25(OH) 2 D may be affected by the seasonal variation of 25(OH)D caused by variation in solar UV irradiance.…”

Changes of 25-OH-Vitamin D during Overwintering at the German Antarctic Stations Neumayer II and III

“…Depending on the latitude, months of complete darkness during the Antarctic winter alternate with months of 24-hrs bright daylight in the Antarctic summer [ 9 ]. This has particular consequences on vitamin D homeostasis for humans residing there [ 10 – 12 ]. Germany currently operates the year-long inhabited research station Neumayer III, which was inaugurated in February 2009; it replaced the previous station Neumayer II, which operated from 1992 to 2009, and which had to be abandoned because its structural integrity could no longer be maintained, as it was located underground within ice [ 13 ].…”