title: The contribution of dietary vitamin D and sunlight to the plasma 25-hydroxyvitamin D in the elderly.
abstract: Total plasma 25-hydroxyvitamin D (25-OHD) and its components 25-OHD2 and 25-OHD3 were measured during the winter in young and elderly healthy persons and in elderly women patients in a long-stay mental hospital. The long-stay patients had no exposure to sunlight or other ultraviolet irradiation, but their diet alone maintained an average total 25-OHD level of 16 nmol/l (range, 10.3-26.5 nmol/l), with most values within the ranges observed in the other two groups, although the average value was lower. The plasma 25-OHD2 which is derived exclusively from vitamin D2 in the diet was similar in all three groups and the vitamin D intake was also similar in the two elderly groups. 25-OHD3 is obtained from the diet as well as from the skin and in the elderly patients the diet alone maintained equal concentrations of 25-OHD2 and 25-OHD3. These findings taken together suggest that the diet accounted for 70 per cent of the total 25-OHD in the active elderly in winter compared with 50 per cent in the young subjects. In all our subjects, young or old, the diet was the major source of vitamin D.
mesh_terms: D015652:25-Hydroxyvitamin D 2; D000328:Adult; D000368:Aged; D002112:Calcifediol / Q000097:blood / Q000378:metabolism*; D004032:Diet; D004872:Ergocalciferols / Q000031:analogs & derivatives / Q000097:blood; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood; D008875:Middle Aged; D005082:Physical Exertion; D012621:Seasons; D012867:Skin / Q000378:metabolism; D013472:Sunlight
chemical_list: D004872:Ergocalciferols; D006887:Hydroxycholecalciferols; D015652:25-Hydroxyvitamin D 2; D002112:Calcifediol