CONCENTRATIONS OF 25-HYDROXYVITAMIN-D3 IN ANTARCTICA

BACKGROUND: Ultraviolet B radiation decidedly influences the synthesis of vitamin D and therefore mineral and bone metabolism. It must also be taken into account that a normal unsupplemented diet is usually deficient in this vitamin. Two groups of subjects pertaining to the Spanish Antarctic Expedition 1988-1989 were studied to determine whether special conditions of irradiation and solar exposure found in Antarctica induce alterations in the abovementioned metabolism. METHODS: Each group consisted of 11 healthy males with ingestion of less than 500 mg/day of calcium. The second group was administered vitamin D3 supplements of 1,000 Ul/day. Two blood samples were performed at an interval of 22 days during the Antarctic summer to determine calcium, phosphorus, magnesium, parathormone (PTH) and 25-hydroxycholecalciferol [25(OH)D]. RESULTS: Neither group varied in calcemia, phosphoremia or magnesemia. In the first group the 25(OH)D decreased markedly (p < 0.01) with no variations being observed in PTH. In the supplemented group, an insignificant increase of 25(OH)D was observed which was significant enough to cause a marked decrease in PTH (p < 0.01). CONCLUSIONS: Subjects passing periods of time in Antarctica should receive vitamin D3 supplementation at doses less than 1,000 Ul/day.