Dietary supplementation and immunocompetence in housebound elderly subjects.

Immune function, particularly cell-mediated immunity (CMI), declines with age and it has been suggested that this may be secondary to the impaired nutritional status often found in the elderly. In the present study a balanced nutritional supplement consisting of several macro- and micro-nutrients was administered daily to 27 housebound elderly (aged 70-85 years) for 12 weeks. Thirty-one matched subjects served as a control group. Delayed cutaneous hypersensitivity (DCH) to seven recall antigens was measured using the Mérieux Multitest CMI device and total numbers of lymphocytes, B-cells, T-cells and T-cell sub-populations were determined using monoclonal antibodies. These tests and several indices of nutritional status were measured before and at the end of the 12-week study. Before supplementation 19% of the entire group of subjects were anergic and another 19% hypoergic, values greater than expected for healthy elderly subjects. A weak association (P = 0.056) was shown between plasma zinc concentration and the number of positive skin test responses. Supplementation had minimal effect on DCH, resulting in a significant (P < 0.05) increase only in the sum of positive indurations. Pre-study numbers of total lymphocytes and lymphocyte sub-populations were as expected for healthy elderly subjects, but a correlation was found between plasma selenium concentrations (mean 1.07, range 0.64-1.66 mumol/l) and the numbers of CD4 lymphocytes (P < 0.01). Supplementation did not result in a significant change in any of the lymphocyte populations.(ABSTRACT TRUNCATED AT 250 WORDS)