A cross-section of an elderly population was assessed in a double-blind trial for the effects of prophylactic vitamin D. The subjects who completed the trial were assessed clinically, by physiotherapy tests of muscle function and by biochemical analysis, before and after a course of vitamin D or placebo.
A significant fall in serum phosphate was found in the placebo group but not in the vitamin D group. The fall was maximal between the months of October and March which correspond to maximum and minimum amounts of circulating 25-hydroxy-vitamin D during the year. No difference in muscle function between treated and untreated groups was shown. Two out of 63 individuals on vitamin D developed hypercalcaemia.
It is concluded that, although there appears to be improvement in the phosphate status of treated patients over the short term of this trial, hypercalcaemia after vitamin D administration precludes the continuous prophylactic use of vitamin D at the levels employed in this trial.