Define the effect of Zinc Deficiency?
Zinc deficiency was identified for the first time in 1940 when malnourished Chinese patients were found to have low concentrations of zinc in blood during war time. The clinical features of severe zinc deficiency in humans are growth retardation, delayed sexual and bone maturation, skin lesions, diarrhoea, alopecia (loss of hair or baldness), impaired appetite, increased susceptibility to infections mediated via defects in the immune system, and the appearance of behavioural changes. The effects of marginal or mild zinc deficiency are less clear. A reduced growth rate and impairments of immune defence are so far the only clearly demonstrated signs of mild zinc deficiency in humans. Other effects, such as impaired taste and wound healing, which have been claimed to result from a low zinc intake, are less consistently observed. The frequency and effects of such mild and moderate deficiency in human population have not been adequately investigated. Growth limiting mild zinc deficiency has been reported in otherwise healthy male American and Canadian infants and preschool children that responded to zinc supplement. In the small areas of Egypt and the Republic of Iran, growth failure in adolescents was found to be responsive to zinc supplements.
Severe zinc deficiency in humans is rare. Many studies have documented that zinc supplementation reduces morbidity from infectious diseases. Reduced activity of the zinc-dependent hormone thymulin, one of the factors responsible for reduced cell mediated immunity may contribute to the increased infectitious morbidity in zinc deficiency. Diarrhoea1 diseases are at the root of an estimated 2 million child deaths in developing countries annually. Studies have shown that an inexpensive 20 mg/day zinc supplement for 7-10 days in combination with oral rehydration therapy can reduce severity of diarrhoea by 40% and duration by 20% ill children. Likelihood of future occurrence of diarrhoea1 disease is also reported to be reduced by zinc supplements; it is now a routine clinical practice to administer zinc supplements to children suffering from diarrhoea. The central role of zinc in cell division, protein synthesis and growth is especially important for infants, children, adolescents and pregnant women; these groups suffer most from an inadequate zinc intake. Zinc-responsive stunting has also been identified in several studies. Thus, prevention of suboptimal zinc status and zinc deficiency in children by an increased intake and availability of zinc could consequently have a significant effect on child health in developing countries, particularly like ours. Even though zinc is an essential requirement for a healthy body, too much zinc can be harmful. We shall now discuss the main features of zinc toxicity.