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Zinc, a mineral, is required in small quantities for multiple metabolic processes. Dietary sources include oysters, beef, and fortified cereals.
Some experts believe that when taken soon after cold symptoms develop, zinc taken as zinc gluconate or acetate lozenges can shorten the course of the common cold. Scientific studies are inconsistent, but if zinc has an effect, it probably is small and occurs only when it is taken very soon after cold symptoms develop.
There is stronger evidence that in developing countries, supplements containing zinc 20 mg and iron taken once/wk reduce mortality in infants who have diarrhea and respiratory infection. There is also strong evidence that supplements containing zinc 80 mg and antioxidants taken once/day slow progression of moderate to severe atrophic (dry form) age-related maculopathy in elderly people.
Zinc is generally safe, but toxicity can develop if high doses are used (see Zinc Toxicity). The common adverse effects of zinc lozenges include nausea, vomiting, diarrhea, mouth irritation, mouth sores, and bad taste. Because zinc is a trace metal and can remove other necessary metals from the body, zinc lozenges should not be taken for more than 14 days. Zinc sprays may cause nose and throat irritation. The effects of certain antibiotics may be lowered by the consumption of zinc supplements.
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