Nutrition has a strong influence on the immune system of the elderly. Aging induces dysregulation of the immune system, mainly as a result of changes in cell-mediated immunity. Aging is associated with changes to the equilibrium of peripheral T and B lymphocyte subsets, such as decreases in the ratios of mature to immature, naive to memory, T helper 1 subset (TH1) to TH2, and CD5- to CD5+ cells. As a consequence, cell-mediated immune responses are weaker and neither cell-mediated nor humoral responses are as well adapted to the
antigen stimulus.
Undernutrition, common in aged populations, also induces lower immune responses, particularly in cell-mediated immunity.
Protein-energy malnutrition is associated with decreased lymphocyte proliferation, reduced
cytokine release, and lower antibody response to
vaccines.
Micronutrient deficits, namely of
zinc,
selenium, and
vitamin B-6, all of which are prevalent in aged populations, have the same influence on immune responses. Because aging and
malnutrition exert cumulative influences on immune responses, many elderly people have poor cell-mediated immune responses and are therefore at a high risk of
infection. Nutritional
therapy may improve immune responses of elderly patients with
protein-energy malnutrition. Supplementation with high pharmacologic doses of a single nutrient (
zinc or
vitamin E) may be useful for improving immune responses of self-sufficient elderly people living at home. Therefore,
nutritional deficiency must be treated in the elderly to reduce infectious risk and possibly slow the aging process.