Ga. Pitson et al., EFFECT OF SEASONAL ULTRAVIOLET-RADIATION FLUCTUATIONS ON VITAMIN-D HOMEOSTASIS DURING AN ANTARCTIC EXPEDITION, European journal of applied physiology and occupational physiology, 72(3), 1996, pp. 231-234
Antarctica is a unique and challenging environment where members of ex
peditions face a range of conditions not normally experienced. Ultravi
olet (uv) radiation levels show marked variation during the year. The
25-hydroxy metabolite of vitamin D [25(OH)D] is largely produced by su
nlight and shows a yearly variation in concentration that corresponds
to uv radiation levels. The active metabolite 1,25-dihydroxyvitamin D
[1,25(OH)2D] does not generally show any such variation provided 25(OH
)D concentrations are sufficient. Previous studies have shown a season
al variation in 25(OH)D with a significant winter drop. No other study
of 1,25(OH)2D has been reported on members of Antarctic expeditions.
A group of 19 men wintering at Davis Station (68 degrees 34' S) had fo
ur blood samples taken at 3-monthly intervals beginning in the Antarct
ic summer. Analysis for 25(OH)D showed a drop in concentration for eac
h of the latter three sampling periods (P<0.005). This correlated with
uv radiation levels and would suggest that endogenous production of 2
5(OH)D ceases for at least the duration of the Antarctic winter. There
were no significant alterations in 1,25(OH)2D or calcium concentratio
ns over the same period. Providing that individuals with pre-existing
vitamin D deficiencies are detected before departure for Antarctica an
d missions are limited in duration, clinical deficiency is unlikely to
occur.