|Description||Zinc is an essential trace mineral.|
|Function/ Used for||Zinc is an important part of many enzymes, some of which have key roles in the formation of new proteins – one of the processes involved in tissue growth. Zinc is required to aid growth of the immune cells plus maintenance of hair, skin and nails.
Superoxide dismutase (a powerful antioxidant enzyme that neutralises potentially damaging free radicals) requires zinc.
Zinc is also essential for reproduction.
EU NRV: 10mg
UK average daily intake
Requirements vary depending on age and gender. The UK National Diet and Nutrition Survey lists up-to-date intake requirements and average intakes1.
|As a supplement||Available as a single supplement. Also commonly available as part of a multivitamin and mineral formula.
Different multivitamin and minerals products will vary in the percentage NRVs they include. People should always check the label for information about a specific product.
|Found in (dietary sources)||Good sources include red meat, liver, shellfish (especially oysters), egg yolks, dairy products, wholegrain cereals and pulses.|
|Deficiency||Signs of mild to moderate deficiency include growth retardation, male hypogonadism (the testes produce few or no sex hormones), poor appetite, rough skin, mental lethargy, delayed wound healing and impaired taste.
Severe zinc deficiency symptoms include alopecia (hair loss), diarrhoea, dermatitis, psychiatric disorders, weight loss, infection (due to impaired immune function), hypogonadism in males, and poor ulcer healing.
Maternal zinc deficiency before and during pregnancy may lead to growth retardation and congenital abnormalities in the foetus.2
|Precautions and contraindications||Those people with liver damage or an intestinal disorder should consult their doctor before taking supplements containing zinc.
Safe Upper Level: 25mg/day3
|Use in pregnancy and breastfeeding||Zinc is suitable to be taken at recommended daily doses during pregnancy and breastfeeding.|
|Interactions e.g. with other medications||High doses of zinc upset absorption of iron and copper. Folic acid and iron reduce zinc absorption.
Zinc may decrease the absorption of some antibiotics – they should be taken two hours before or four to six hours after taking a zinc supplement.
Zinc can also reduce the absorption and action of penicillamine, a drug used to treat rheumatoid arthritis – they should be taken two hours apart.
Long term use of oral contraceptives may reduce zinc levels.2,4
|Adverse effects||Signs of acute toxicity (doses >200mg daily) include gastrointestinal pain, nausea, vomiting and diarrhoea.
Prolonged exposure to doses >50mg daily may induce copper deficiency and iron deficiency. Doses >150mg daily may reduce serum HDL-cholesterol levels, depress immune function and cause gastric erosion.2
2. Mason, P. Dietary Supplements. Pharmaceutical Press, London, 2001.
4. Gaby, A. R. A-Z Guide to Drug-Herb-Vitamin Interactions. HealthNotes 2006.