Zinc is an essential mineral that is important for immune function, wound healing, normal taste and smell, and is needed for DNA synthesis. Zinc also supports normal growth and development during pregnancy, childhood, and adolescence.
- Zinc is a co-factor in DNA and protein synthesis and cell division. It is believed to be important in wound healing.
- The UK recommended ranges are 5.5-9.5 mg/day for males and 4.0-7.0 mg/day for females.
- Zinc is not stored in the body but the body contains 2 to 3 g of zinc (Zn), found mainly in bones, teeth, hair, skin, liver, muscle, leucocytes and testes.
- One third of the of zinc found in plasma is attached loosely to albumin and about two thirds is firmly bound to globulins.
- Meat, liver, cereal products, peas, beans, eggs, and seafood (especially oysters) are good sources of zinc.
- Absorption of zinc salts from food is approximately 20-40%. Absorption of zinc is higher from fish and meat but lower from wholegrain bread and cereals (phytate content impairs absorption).
- Zinc is mainly excreted from body in faeces.
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- Excessive loss of zinc can occur in trauma, burns and other protein-losing conditions, eg protein-losing enteropathy.
- Liver disease.
- Inadequate diet or malabsorption.
- Prolonged parenteral nutrition (total parenteral nutrition usually includes trace amounts of zinc).
Presentation of zinc deficiency
Presentation depends on the severity of zinc deficiency. Mild deficiency may cause no obvious symptoms, whereas severe deficiency may cause most or even all of the following features:
- Anorexia, lethargy, diarrhoea
- Growth retardation, delayed sexual maturation, hypogonadism and hypospermia
- Alopecia, dermatitis, paronychia
- Mental retardation, impaired nerve conduction and nerve damage
- Immune disorders and susceptibility to infections
- Iron deficiency anaemia
- Macular degeneration, night blindness
- Impaired taste and smell
- Impaired wound healing
Maternal zinc deficiency may cause anencephaly in the fetus.
Diagnosis may be difficult to confirm, particularly with mild levels of deficiency.
- Decreased levels of plasma zinc (less than 10.7 μmol/L). Plasma levels are an unreliable indicator of zinc deficiency because the plasma level may be lowered, eg in acute infection and after trauma. Hypoproteinaemia spuriously lowers the measured plasma zinc concentration.
- Reduced alkaline phosphatase and plasma testosterone.
- Impaired T-lymphocyte function.
- Decreased collagen synthesis (resulting in poor wound healing), and decreased RNA polymerase activity in several tissues.
Management is based on both treatment of any underlying cause and zinc supplementation. Zinc deficiency often coexists with other micronutrient deficiencies including iron, making single supplements inappropriate.
- Dietary advice and zinc supplementation if necessary (see also separate articles Zinc Supplements and Zinc Excess and Zinc Toxicity).
- Zinc supplementation has a positive effect on growth in premature infants.
- There is weak evidence that zinc supplementation may help to heal leg ulcers in patients with low serum zinc.
- Symptoms usually begin after an infant is weaned from breast milk.
- Presents with psoriasiform dermatitis (characteristic pustular rash over the mucocutaneous junctions, particularly the mouth, the genital areas and pressure areas), hair loss, paronychia, failure to thrive and severe diarrhoea. Also leads to secondary bacterial and fungal infections.
In older children, failure to thrive, anorexia, alopecia, nail dystrophy, and repeated infections are more common.
Similar clinical manifestations are seen in children or adults with zinc deficiency from any cause.
- Oral zinc sulphate supplements: if treated early, most of the symptoms are reversible and usually leave no sequelae. Therapy is lifelong and total compliance is essential.
Further reading & references
- Food Standards Agency; Zinc
- Eastwood M; in Oxford Textbook of Medicine 3rd Ed OUP 2003
- Shrimpton R, Gross R, Darnton-Hill I, et al; Zinc deficiency: what are the most appropriate interventions? BMJ. 2005 Feb 12;330(7487):347-9.
- British National Formulary
- Diaz-Gomez NM, Domenech E, Barroso F, et al; The effect of zinc supplementation on linear growth, body composition, and growth factors in preterm infants.; Pediatrics. 2003 May;111(5 Pt 1):1002-9.
- Wilkinson EA, Hawke CI; Oral zinc for arterial and venous leg ulcers.; Cochrane Database Syst Rev. 2000;(2):CD001273.
- Wilkinson EA, Hawke CI; Does oral zinc aid the healing of chronic leg ulcers? A systematic literature review.; Arch Dermatol. 1998 Dec;134(12):1556-60.
- Online Mendelian Inheritance in Man (OMIM); Acrodermatitis Enteropathica; Online Mendelian Inheritance in Man (OMIM)
- Subramanian KNS, Silverman RA; Acrodermatitis Enteropathica; eMedicine, September 2008.
|Original Author: Dr Colin Tidy||Current Version: Dr Colin Tidy|
|Last Checked: 22/03/2010||Document ID: 570 Version: 22||© EMIS|
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