title: Serum levels of 25-hydroxyvitamin D in a year of residence on the Antarctic continent.
abstract: OBJECTIVE
  Since exposure to sunlight is the main source of vitamin D in human beings and skin photosynthesis decreases markedly as the latitude increases, we studied the changes in serum 25-hydroxyvitamin D (25(OH)D) levels in young healthy men who lived in the Antarctic Continent during 1 year.
  
  
  METHODS
  Blood was drawn in the fasting state every 2 months from March 1990 to January 1991 to determine the serum levels of calcium, alkaline phosphatase and 25(OH)D.
  
  
  METHODS
  19 healthy volunteers, who left Buenos Aires (34 degrees S) during the 1990 summer, arriving at the Antarctic bases at the end of January (Belgrano) and in mid-March (San Martín) and stayed there up to summer 1991.
  
  
  RESULTS
  Serum calcium did not change significantly throughout the year. Serum alkaline phosphatase levels were not different comparing the beginning to the end of the year, but autumn and winter levels were lower (P < 0.05). At Belgrano Base the serum 25(OH)D levels (ng/ml) decreased from (mean +/- SD) 18.7 +/- 7.4 (March) to 10.0 +/- 4.3 (July) (P < 0.005) and did not recover for the rest of the year. At San Martín Base the serum 25(OH)D levels descended from 22.0 +/- 5.4 in March to 12.2 +/- 3.7 in August (P < 0.02) and did not increase even at the beginning of summer (January) except in two men with frequent outdoor activities.
  
  
  CONCLUSIONS
  The levels of 25(OH)D of healthy men living in the Antarctic continent decreased to approximately 46% of the initial values and did not increase even at the onset of summer. Further studies should determine the effect of these changes upon calcium-regulating hormones and bone metabolism.
authors.affiliation: Sección Osteopatías Médicas, Hospital de Clínicas, Universidad de Buenos Aires, Argentina.
authors.forename: M B
authors.initials: MB
authors.lastname: Oliveri
authors.forename: C
authors.initials: C
authors.lastname: Mautalen
authors.forename: L
authors.initials: L
authors.lastname: Bustamante
authors.forename: V
authors.initials: V
authors.lastname: Gómez García
mesh_terms: D000328:Adult; D000469:Alkaline Phosphatase / Q000097:blood; D000864:Antarctic Regions; D002112:Calcifediol / Q000097:blood*; D002118:Calcium / Q000097:blood; D004641:Emigration and Immigration; D005215:Fasting; D006801:Humans; D007899:Leisure Activities; D008297:Male; D012111:Residence Characteristics; D012621:Seasons; D013472:Sunlight
chemical_list: D000469:Alkaline Phosphatase; D002112:Calcifediol; D002118:Calcium