Undernutrition, infection and immune function

Undernutrition and infection are the major causes of morbidity and mortalit y in the developing world. These two problems are interrelated. Undernutrit ion compromises barrier function, allowing easier access by pathogens, and compromises immune function, decreasing the ability of the host to eliminat e pathogens once they enter the body. Thus, malnutrition predisposes to inf ections. Infections can alter nutritional status mediated by changes in die tary intake, absorption and nutrient requirements and losses of endogenous nutrients. Thus, the presence of infections can contribute to the malnouris hed state. The global burden of malnutrition and infectious disease is imme nse, especially amongst children. Childhood infections impair growth and de velopment. There is a role for breast-feeding in protection against infecti ons. Key nutrients required for an efficient immune response include vitami n A, Fe, Zn and Cu. There is some evidence that provision of the first thre e of these nutrients does improve immune function in undernourished childre n and can reduce the morbidity and mortality of some infectious diseases in cluding measles, diarrhoeal disease and upper and lower respiratory tract i nfections. Not all studies, however, show benefit of single nutrient supple mentation and this might be because the subjects studied have multiple nutr ient deficiencies. The situation regarding Fe supplementation is particular ly complex. In addition to immunization programmes and improvement of nutri ent status, there are important roles for maternal education, improved hygi ene and sanitation and increased supply of quality water in the eradication of infectious diseases.