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Childhood malnutrition has long been associated with a wide range of adverse outcomes, including an increased risk of morbidity and death from infectious diseases, impaired immunity, and delayed motor and cognitive development. Recent analyses indicate that poor anthropometric status may be the underlying cause of more than half of the childhood deaths in developing countries. When these associations were first noted more than 30 years ago, malnutrition was thought to be due to inadequate dietary protein, or later to insufficient dietary energy intake. Since then, it has been recognized that malnutrition is more complex and usually includes deficiencies of one or more micronutrients.
Zinc deficiency may be another example of a micronutrient deficiency that is highly prevalent and that has broad, adverse consequences. It is likely that zinc deficiency is widespread in developing countries with particular effects in pregnancy and early childhood. Evidence is accumulating that this deficiency leads to complications of pregnancy and childbirth, lower birth weight and poor growth in childhood, reduced immunocompetence, and increased infectious disease morbidity. Since childhood infectious disease morbidity from diarrhea, pneumonia, and malaria is the cause of most of the childhood deaths in developing countries, it is also plausible that zinc deficiency contributes to the elevated mortality rates still seen in many developing countries. zinc supplementation had a highly statistically significant effect of small magnitude on linear growth and weight gain.
Children who were stunted at baseline had a moderately large effect of zinc supplementation on linear growth, while non-stunted children had no effect. With weight gain, the magnitude of the effect of zinc supplementation was inversely related to plasma zinc concentration at baseline. Poor nutrition can affect cognitive development through poor growth, increased illness, inhibited central nervous system development, and reduced activity leading to inferior motivation and exploration. Zinc is also necessary for estrogen-dependent functions such as expulsion of the placenta and coordination of uterine muscles during birth, and mild-to-moderate zinc deficiency during pregnancy has been shown to increase problems during parturition.
Recent studies have demonstrated that zinc supplementation has both therapeutic and preventive benefits in regard to childhood infectious diseases. Zinc supplementation has been shown to reduce the duration and severity of diarrhea and to reduce the occurrence of diarrhea, respiratory infections, including pneumonia, and malaria, while improving immunocompetence. These studies in developing countries also indicate that with zinc supplementation, growth is improved, as are motor and cognitive aspects of child development.
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