Immunology, nutritional aspects

The role of nutrition is central to the development and modulation of the immune system . The importance of nutrition has been made clear by the burgeoning field of sports medicine. It appears the immune system is enhanced by moderate to severe exercise, although many components of the immune response exhibit adverse change for a period of from 3 to 72 hours after prolonged intense exertion. This "window of opportunity" for opportunistic bacterial and viral infections seems to be increased for "elite" athletes that are more prone to over-train. The elements of the immune response most affected by the strenuous activity that leads to the impairment of the immune system are lymphocyte concentrations, depressed natural killer activity, and elevated levels of IgA in the saliva.

The possible basis for this prolonged immunosuppression may include reduced plasma glutamine concentrations, altered plasma glucose levels, and proliferation of neutrophils and monocytes that increases prostaglandin concentrations. Exercise produces oxidative stress and so concomitantly, there are elevated free radical levels along with an attendant depletion of antioxidant levels. Therefore, antioxidants that help protect against oxidative stress are considered the most promising for further study, but those nutrients that heal the gut show potential also. These nutrients include Vitamin E, Vitamin C, zinc, and glutamine. Glutamine and nucleotides show a direct effect on lymphocyte proliferation. Free radicals and other reactive oxygen species that can damage cells as well as tissues are an integral part of the immune system, so the body has developed systems that protect from their damage. These products function by destroying invading organisms and damaged tissues, as well as enhance interleukin-I, Interleukin-8 and tumor necrosis factor concentrations as part of the inflammatory response. The purpose of supplementing the diet is to provide a balance to the immune system's pro-oxidant function. Carbohydrate supplementation has additionally shown impressive results. Increased plasma levels, a depressed cortisol and growth hormone response, fewer fluctuations in blood levels of immune competent cells, decreased granulocyte and monocyte phagocytosis , reduced oxidative stress and a diminished pro-inflammatory and anti-inflammatory cytokine response are all associated with an increase in complex carbohydrate consumption.

Besides exercise-associated immune suppression, malnutrition plays a pivotal role in modulating the immune response. Nowhere is this more important then during pregnancy and gestation. Besides genetics, no other factor is more important for the developing immune system then optimal nutrition. The immune response of low-birth-weight babies is compromised as well as those of children born to mothers without adequate nutrition. Especially important is the role of Vitamin E and selenium in preventing immune impairment. Animal studies showed that progeny of Vitamin E and selenium-deficient mothers never adequately developed immune competent cell lines.

Because nutrition plays such a vital role in the immune response, a special branch of immunology is developing called immunonutrition. These scientists are particularly interested in the interaction of genetics and nutrition. Preliminary work suggests that individual genotypes vary in their response to healing, infection, and dietary supplementation.

See also Immunogenetics; Infection and resistance; Metabolism