Zinc is an essential trace element that is vital for growth and development. Zinc is instrumental in immune response, brain function and the ability to reproduce. There is also conflicting data suggesting that zinc supplements might be able to reduce symptoms of the common cold.
Function of Zinc
Zinc is essential for the proper function of cellular metabolism. About 100 enzymes rely on zinc to help them catalyse vital chemical reactions. Zinc protects cell membranes from oxidative damage and stabilises the structure of cell proteins. Zinc proteins bind to DNA and help the genes tell cells what to do. This includes telling certain cells to die, which is important for growth, gestation and disease prevention. Zinc also helps control the release of hormones and the transmission of nerve impulses.
Daily Recommended Allowances of Zinc
The recommended daily allowance of zinc varies for different types of people. Babies up to 6 months old should consume about 2 mg of zinc per day. This increases to 3 mg per day for children 7 months to 3 years old. Children 4 to 8 years old should get 5 mg of zinc per day. Children 9 to 13 years old should consume 8 mg.
The optimal amount of zinc in a diet differs between men and women after age 14. The recommended daily allowance for men is 11 mg of zinc per day; women only require 9 mg per day, except when they are pregnant or lactating. Pregnant women should get 13 mg of zinc per day, while lactating women should consume 14 mg per day.
Benefits of Zinc-Rich Foods
People can benefit from eating zinc-rich foods. These include red meat, poultry, crab, lobster, nuts, beans, milk, yoghurt, cheese, whole grain bread and fortified breakfast cereal. The food with the most zinc is oysters--a serving of 6 oysters has 76.7 mg of zinc. The tolerable upper intake level for an adult is 40 mg of zinc, so it is advisable to eat no more than 3 oysters per day.
Warning: Too Much or Too Little Zinc
Doctors warn against consuming too much or too little zinc. Too much zinc leads to zinc toxicity. Symptoms include vomiting, diarrhoea, abdominal cramps and severe headache. High zinc levels interfere with the body's absorption of copper and iron. This can lead to a weakened immune system and anaemia. Too little zinc can lead to zinc deficiency. Symptoms include stunted growth, weigh loss, skin lesions and hair loss. Vegetarians, pregnant women and alcoholics are all potentially in danger of zinc deficiency. They can benefit from zinc supplements or eating zinc-rich foods.
Zinc and the Common Cold
It is a controversial belief that zinc lozenges, gels and sprays decrease the length and severity of the common cold. Anyone thinking about taking zinc to treat a cold should consider the scientific data. At least 14 major studies have examined the link between zinc and the common cold. About half found that zinc alleviated cold symptoms and reduced sick days. The other half found that zinc did no better than a placebo. Therefore, scientists consider the research inconclusive.