Nutrition and immunity

Abstract

SummaryIt is well recognised that dietary factors play an important role in maintaining immune defences. Malnourished populations are known to have increased incidence and duration of infectious diseases, and data from numerous clinical and experimental studies have demonstrated impaired immunocompetence in the malnourished host. Restoring the food supply to an affected individual restores cell‐mediated immunity, except when malnutrition has occurred during foetal development. The developing immune system is particularly susceptible to nutritional deprivation. The problem of malnourishment is not restricted to developing countries. Malnutrition has been reported among hospitalized patients, generally as a result of illness but also as a consequence of surgery and sometimes from inappropriate feeding regimes. Alterations of the immune response can be demonstrated in obesity as well as in the malnourished state, and excess intake of polyunsaturated fatty acids (PUFA) has been shown to suppress immunity. Vitamins and trace minerals are also important in maintaining immunocompetence. Selenium and vitamin E have enhancing effects, probably due to their ability to prevent peroxidation of PUFA, and deficiency of pyridoxine (B6), zinc and vitamin A has been associated with impairment of immune functions. Knowledge gained of the interactions between nutritional factors and immunity offer the possibility of altering dietary regimes in order to modulate immune function and thus improve resistance to infectious disease and other diseases associated with impaired immunity.