© CAB International 2002. Nutrition and Immune Function (eds P.C. Calder, C.J. Field and H.S. Gill)

Health, 1991). The estimated average requirement for adults in the UK is about 7 (men) and 5.5 (women) mg day-1 (Department of Health, 1991). In persons suffering from marginal Zn deficiency (intake less than 5 mg day-1), clinical signs consist of depressed immunity, impaired taste and smell, onset of night-blindness, impairment of memory and decreased spermatogenesis in males (Prasad et al., 1961; Sandstead et al., 2000). Severe Zn deficiency is characterized by severely depressed immune function, frequent infections, bullous pustular dermatitis, diarrhoea, alopecia and mental disturbances (Barnes and Moynahan, 1973). Similar effects of mild and severe Zn deficiency arise in Zn-deficient laboratory animals (see Shankar and Prasad, 1998). A rare genetic disorder, known as acrodermatitis enteropathica (AE), occurs in cattle and humans, resulting in decreased Zn absorption, accompanied by characteristic hyperpigmented skin lesions, poor growth and low plasma Zn levels (Walsh et al., 1994). It is estimated that nutritional Zn deficiency may affect approximately 2000 million people in the developing world.

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