Effect of infections and environmental factors on growth and nutritional status in developing countries.

Despite numerous advances and improvements in child health globally, malnutrition remains a major problem and underlies a significant proportion of child deaths. A large proportion of the hidden burden of malnutrition is represented by widespread single and multiple micronutrient deficiencies. A number of factors may influence micronutrient deficiencies in developing countries, including poor body stores at birth, dietary deficiencies and high intake of inhibitors of absorption such as phytates and increased losses from the body. Although the effects of poor intake and increased micronutrient demands are well described, the potential effects of acute and chronic infections on the body's micronutrient status are less well appreciated. Even more obscure is the potential effect of immunostimulation and intercurrent infections on the micronutrient distribution and homeostasis. The association therefore of relatively higher rates of micronutrient deficiencies with infectious diseases may be reflective of both increased predisposition to infections in deficient populations as well as a direct effect of the infection itself on micronutrient status indicators. Recently the association of increased micronutrient losses such as those of zinc and copper with acute diarrhea has been recognized and a net negative balance of zinc has been shown in zinc metabolic studies in children with persistent diarrhea. It is also recognized that children with shigellosis can lose a significant amount of vitamin A in the urine, thus further aggravating preexisting subclinical vitamin A deficiency. Given the epidemiological association between micronutrient deficiencies and diarrhea, supplementation strategies in endemic areas are logical. The growing body of evidence on the key role of zinc supplementation in accelerating recovery from diarrheal illnesses in developing countries supports its use in public health strategies.