Recommended Nutrient Intakes for Vitamin and Minerals

Zinc

Functions

Zinc is a trace element that is involved in over 150 enzymes. Most cells contain zinc, but is in highest concentration in the bone, prostate and eye. Zinc is also important for the immune system, and for growth and development, blood clotting, thyroid hormone function, and behaviour and learning performance. Zinc is also necessary to produce the active from of vitamin A and is essential for normal taste perception, wound healing, the making of sperm and foetal development. It can also function as an antioxidant.

Recommended Intakes

Table: Recommended Intakes for Zinc (mg/day)

Food Sources

Zinc is widely distributed in many foods, but many factors affect its bioavailability. The zinc in animal products, crustacea and molluscs is more readily absorbed than from plant sources.

Rich sources of zinc include oysters red meat and liver. Unrefined cereal grains and legumes are rich in phytate, which reduces zinc absorption.

Deficiency

Zinc deficiency clearly effects growth and maturation. It was first described in male adolescents in Iran, Turkey, and Egypt. The diets of these countries are typically low in zinc and contain foods high in fibre and phytates (e.g. unleavened bread and wholegrain foods), which inhibit zinc absorption. Deficiency was marked by severe growth retardation and delayed sexual maturation. Other symptoms of zinc deficiency include skin lesions, impaired wound healing, hypoguesia, behavioural disturbances, night blindness, and immune deficiency.

Toxicity

Accidental high intakes of zinc (>2g) may cause vomiting, diarrhoea, fever, exhaustion. Doses of zinc not far above the RNI, taken over time may lower the body's copper content. Large doses also alters cholesterol metabolism (i.e. increase LDL-cholesterol and decrease HDL-cholesterol) and may accelerate the development of atherosclerosis.