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Thursday, April 14, 2011

Minerals (1)

The daily RNI for men is 160 μmol (8.7 mg) and for women 260 μmol (14.8 mg). Iron deficiency is common world-wide, affecting both developing and developed countries. It is particularly prevalent in women of a reproductive age. Dietary iron overload is seen in South African men who cook and brew in iron pots.

The daily RNI of copper is 1.2 mg (19 μmol). Shellfish, legumes, cereals and nuts are good dietary sources.

Menkes' kinky hair syndrome is a rare condition caused by malabsorption of copper. The Menkes' disease gene (ATP7A) encodes a copper-transporting ATPase and has a homology to the gene in Wilson's disease. Infants with this sex-linked recessive abnormality develop growth failure, mental retardation, bone lesions and brittle hair. Anaemia and neutropenia also occur. This condition, which serves as a model for copper deficiency, supports the idea that some of the clinical features seen in PEM are due to copper deficiency. Breast and cow's milk are low in copper, and supplementation is occasionally necessary when first treating PEM.

The daily RNI of zinc is 9.5 mg (145 μmol) for men, 7 mg (110 μmol) for women and it is widely available in food. Zinc is involved in many metabolic pathways, often acting as a coenzyme; it is essential for the synthesis of RNA and DNA.

Acrodermatitis enteropathica is an inherited disorder caused by malabsorption of zinc. Infants develop growth retardation, severe diarrhoea, hair loss and associated Candida and bacterial infections. This condition provides a model for zinc deficiency. Zinc supplementation results in a complete cure. Deficiency probably also plays a role in PEM.

Zinc levels have been shown to be low in some patients with malabsorption or skin disease, and in patients with AIDS, but the exact role of zinc in these situations is disputed. Zinc has low toxicity, but high zinc levels from water stored in galvanized containers interfere with iron and copper metabolism. Wound healing is impaired with moderate zinc deficiency and is improved by zinc supplements. Impaired taste and smell, hair loss and night blindness are also features of severe zinc deficiency.

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