Inadequate status and impaired metabolism of vitamin D in the elderly.

The mean serum concentrations of 25-hydroxyvitamin D and of 24,25-dihydroxyvitamin D were significantly lower (P less than 0.01) in 82 elderly people than in 30 young control subjects. The levels in 30 elderly people confined to their rooms were 8.0 +/- 0.7 (SE) and 0.54 +/- 0.04 ng/ml, respectively; in 31 active old-age-home residents who spent part of their time outdoors, they were 11.4 +/- 0.8 and 0.82 +/- 0.08 ng/ml, respectively; and in 21 elderly farm workers, 14.6 +/- 1.4 and 0.98 +/- 0.10 ng/ml, respectively. In the young control subjects, the levels were 21.5 +/- 1.4 and 1.91 +/- 0.12 ng/ml, respectively. In addition, an intestinal absorption test with a standard oral dose of 25-hydroxyvitamin D3 showed that the serum 25-hydroxyvitamin D3 responses at 4 and 6 h were considerably depressed in 10 of the 20 elderly subjects in whom the test was performed.