Too much versus too little ZINC (Zn)

Zinc is stored in enzymes in the liver, kidneys, pancreas, pituitary gland, adrenal glands, bones, muscles, skin, hair and nails. Intense and prolonged physical effort lowers the level of zinc, which is excreted through sweat, and the body's stores are used up quickly.

Zinc plays an important role in the sensory system, which controls food intake and brain functions and increases the ability to learn and remember. Without zinc the body cannot use vitamin A. It also plays an important role in strengthening the immune system, in maintaining the acid-base balance, the pH value and the water and sodium balance. Zinc contributes to normal cognitive function and to the normal function of the immune system.

A lack of zinc is due first and foremost to an insufficient intake from food, a large part of it being destroyed during cooking. A diet low in protein can also lead to a lack of zinc (it binds to protein).

The symptoms of a zinc deficiency are:

• a change in taste and smell (a salty, sweet or metallic taste when no food is being eaten);
• visual disturbances that can lead to blindness;
• loss of hair and eyelashes, brittle nails that can become deformed and show white spots;
• psychomotor retardation, insomnia, irritability, apathy.

An excess of zinc is rarer and is often linked to poisoning from galvanised containers in which food is stored, which release zinc into it as they corrode. The acidity of the food favours the dissolving of zinc and so creates the conditions for possible poisoning.

The most important sources of zinc are drinking water, meat, fish, liver, eggs, beef sprouts, barley, beetroot, cabbage, spinach, tomatoes, peaches, oranges, walnuts, linseed, pumpkin and sesame.

A vegetarian diet goes hand in hand with a lack of zinc, and supplementing it is also recommended for heavy drinkers, for older people prone to senility (combined with manganese), for athletes and in cases of irregular menstrual cycles, diabetes and prostate problems.