Zinc is an essential mineral that is found in almost every one of our cells. Our bodies contain about 2 to 3 grams of zinc, however there are no specific storage sites known for this mineral and so a consistent supply in your diet is necessary.
Zinc has a wide range of functions. It is pivotal in insulin activity, in the metabolism of the testes and ovaries and in liver function. It also plays a crucial role in growth and cell division, where it is required for protein and DNA synthesis. As a component of over 100 enzymes, zinc is also involved in the metabolism of proteins, carbohydrates, lipids and energy.
Zinc is particularly important for healthy skin and is essential for a healthy immune system and resistance to infection. This mineral also supports normal growth and development during pregnancy, childhood and adolescence. It is thought that zinc can help skin conditions such as acne and eczema, and can shorten the duration of the common cold when taken as a supplement. Those suffering from prostate problems, anorexia nervosa, alcoholism and those going through trauma or convalescence also seem to benefit from an extra supply of zinc.
The first signs of a zinc deficiency are impairment of taste, a poor immune response and skin problems. Other symptoms can include hair loss, diarrhoea, low energy, delayed wound healing, and a decreased growth rate and mental development in infants.
At the other end of the scale, excess zinc is toxic. Too much zinc interferes with the metabolism of other minerals in the body, particularly iron and copper. The symptoms of zinc toxicity include nausea, vomiting and fever.
A good food source of zinc contains a substantial amount of zinc in relation to its calorie content and contributes at least 10% of the US Recommended Dietary Allowance (RDA) for zinc in a selected serving size. The RDA for zinc is 15 milligrams per day for adults (except pregnant or lactating women) and children over 4 years of age.
Oysters contain more zinc per serving than any other food, but red meat and poultry provide the majority of zinc in the typical ‘western’ diet. Other good food sources include beans, nuts, certain seafood, whole grains, fortified breakfast cereals and dairy products A vegetarian diet often contains less zinc than a meat based one and so it is important for vegetarians to eat plenty of foods that are rich in this vital mineral.
Only 20% of the zinc present in the diet is actually absorbed by the body. Fortified foods (including many breakfast cereals) make it easier to consume the RDA of zinc, however they also make it easier to consume too much zinc, especially if supplemental zinc is being taken. This is why it is important to seek professional advice before taking a zinc supplement. In many instances, an individual’s needs could easily be met by dietary zinc sources.
Certain substances may have irreversible harmful effects if taken for long periods at the highest supplemental doses. These include beta-carotene, nicotinic acid, manganese, phosphorus and also zinc. The UK’s Food Standards Agency advises that you should not take high doses of zinc over long periods, as this may prove harmful to your health.