Vitamin D status in the extreme age of life.

The aim of the present study was to investigate vitamin D status in the extreme age of life and to assess the ability of elderly people to synthesize vitamin D in skin, in response to artificial ultraviolet irradiation, and to hydroxylate the newly synthesized vitamin in the liver. The authors have determined the serum 25-hydroxyvitamin D concentrations in 43 healthy subjects (17 males and 26 females) aged 84 years or more. The changes induced in 25-OHD serum levels by whole-body artificial ultraviolet irradiation have also been studied in 10 healthy volunteers aged 41-90 years and, as a control, in 8 normal subjects aged 24-40 years. Serum 25-OHD has been determined, after lipid extraction of samples and column chromatography, by competitive protein binding assay using rat serum as the source of binding protein. The mean 25-OHD serum level in the group studied was 5.7 +/- 4.3 ng/ml, much lower than the mean observed in normal subjects aged 20-40 years (21.3 +/- 8.2 ng/ml). Men had higher levels than women. In the age group 84-89 years 25-OHD levels were higher than in subjects aged 90-96. Serum 25-OHD increased remarkably in all our normal subjects in response to artificial ultraviolet irradiation. Age-related differences in 25-OHD response to irradiation were not significant. The results of the present study indicate that vitamin D deficiency is common in the extreme age of life. It is probably a consequence of poor diet and lack of exposure to sunshine rather than of an impairment of cutaneous synthesis or liver hydroxylation of vitamin D.