Who Needs Zinc?
This Micronutrient Is Crucial to Cellular Function and Health
May 6, 2009 Stephen Allen Christensen
Zinc is a micronutrient found in a variety of foods, including meats, seafood, yogurt, nuts, and beans. However, since such foods are relatively scarce in many developing nations, zinc deficiency due to malnutrition is associated with nearly two million deaths annually. (World Health Organization. The World Health Report, 2002: Reducing Risks, Promoting Healthy Life. Geneva, Switzerland: WHO; 2002)
Zinc is the catalyst in at least 100 intracellular enzymatic reactions. It is involved in the critical process of protein folding and the regulation of gene expression.
Zinc is instrumental in wound healing, regeneration of epithelial cells, vitamin metabolism, nutrient absorption, hormone and immune function, cell membrane stability, and protection from oxidative stress.
Serum zinc levels are an unreliable measure of total body zinc stores, so blood tests are not recommended for evaluating zinc status. The diagnosis of zinc deficiency is based on the presence of malnutrition and/or other conditions known to be associated with zinc deficiency.
Because zinc is so important in physiologic processes, zinc supplements are purported to relieve a variety of conditions, including HIV infection, colds and flu, skin diseases, diarrhea, and age-related macular degeneration.
Zinc for Age-Related Macular Degeneration
Zinc in combination with antioxidants (beta-carotene and vitamins C and E) may slow the progression of intermediate and advanced stages of age-related macular degeneration in well-nourished individuals between the ages of 55 and 80 years. Some studies also show a possible association between zinc supplementation and a reduced risk of developing ARMD.
(Evans J. Antioxidant vitamin and mineral supplements for slowing the progression of age-related macular degeneration. Cochrane Database Syst Rev. 2006;(2):CD000254 and Tan J, et al. Dietary antioxidants and the long-term incidence of age-related macular degeneration: the Blue Mountains Eye Study. Ophthalmology. 2008;115(2):334-341)
Zinc for Diarrhea
In developing countries, zinc supplementation reduces symptoms and incidence of diarrheal illnesses in children by 15 to 20%, an effect that might simply be due to correction of zinc deficiency. No data exist regarding the effects of zinc on childhood diarrhea in developed nations. (Lukacik M, et al. A meta-analysis of the effects of oral zinc in the treatment of acute and persistent diarrhea. Pediatrics. 2008;121(2):326-336)
Zinc for Upper Respiratory Infections (Colds)
Children in developing nations suffer fewer upper respiratory infections when they use zinc supplements, but evidence for zinc’s ability to reduce the severity or duration of colds in industrialized nations is lacking.
Zinc for Wound Healing
Zinc deficiency is associated with poor wound healing, but no study to date shows any benefit from treating surgical wounds, leg ulcers, or diaper dermatitis with topical zinc.
Zinc for Wilson Disease
Wilson disease is characterized by the over-absorption and subsequent accumulation of copper in tissues. Zinc competes with copper for absorption and tissue binding sites; therefore, treatment with zinc helps to retard the progression of Wilson disease.
Zinc for HIV
HIV progresses more rapidly in zinc-deficient individuals, but supplementation with zinc does not increase CD4 counts or decrease viral load. Indeed, some evidence indicates that HIV, which requires zinc for replication, may multiply more rapidly in the face of zinc supplementation.
(From Saper R, Rash R. Zinc: An essential micronutrient. Am Fam Phys. 2009;79(9):768-772)
Zinc is an essential micronutrient. In people who are already well-nourished, the benefits of supplementation are questionable. However, ongoing zinc supplementation up to the tolerable upper intake level (40 mg elemental zinc in adults) is generally safe. Non-smoking individuals with age-related macular degeneration should consider taking 80 mg of zinc daily in combination with 500 mg vitamin C, 400 IU vitamin E, and 15 mg beta-carotene. Smokers should avoid beta-carotene due to a putative increase in the risk for cancer.
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