The influence of sunlight or dietary vitamin D on plasma 25‐hydroxyvitamin D in institutionalized elderly patients in a sub‐tropical climate

Plasma 25‐hydroxyvitamin D (25(OH)D) concentrations in a group of thirty‐eight nursing‐home residents (age range 55–95 years) living in a sub‐tropical climate (Brisbane, Australia) were less than 25 nmol/1 in 50% of cases. The effects of endogenously and exogenously derived vitamin D have been studied over three months (April‐June) using the following treatment groups: A, placebo; B, daily sun exposure; C, 18.8 nmol vitamin D/day and D, 56.3 nmol vitamin D/day. Exposure to ultra‐violet radiation of group B patients was monitored by meter and polysulphone film. Group D exhibited a significant increase in Plasma 25(OH)D (P‐CO.001) after one month of treatment and groups B and C, respectively, after two months (P < 0.01). No significant changes were observed in plasma concentrations of creatinine, calcium, phosphate and alkaline phosphatase during the study period. A daily oral supplement of vitamin D in the range 18.8–56.3 nmol is proposed as the treatment of choice. It provides a safe and effective means of protection for elderly, institutionalized people against the effects of vitamin D deficiency.