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Zinc May Shorten Cold But May Cause Side Effects

A new study supports previous findings that suggest zinc may shorten the duration of the common cold in adults; however, side effects may be common.

Zinc is necessary for the functioning of more than 300 different enzymes and plays a vital role in a large number of biological processes. Zinc is a cofactor for the antioxidant enzyme superoxide dismutase (SOD) and is in a number of enzymatic reactions involved in carbohydrate and protein metabolism.

In previous research, there have been conflicting results regarding the effect of zinc formulations in treating the duration and severity of common cold symptoms. Although zinc may be beneficial in the treatment of cold symptoms if taken at the onset of symptoms, more studies are needed to clarify which zinc formulations may be most effective, which rhinoviruses are affected by zinc and if nasal sprays provide a useful alternative application route for zinc treatment. Negative results may be caused by using doses of zinc that are too low, or they may be affected by the presence of compounds like citric or tartaric acid, which may reduce efficacy due to chelating of the zinc ion.

In a new study, researchers conducted a comprehensive literature search for well-designed clinical trials comparing zinc taken by mouth with placebo or no treatment at all. Seventeen trials evaluating a total of 2121 participants were ultimately identified for inclusion.

The researchers found that participants who received zinc experienced cold symptoms for less time than those who received placebo. However, the authors noted that these effects were only significant in adults, not children. Furthermore, side effects, including nausea and bad taste, were more common in participants taking zinc.

The authors concluded that although zinc may shorten the length of a cold, further research is needed to form a firm conclusion and evaluate potential side effects.

Many other integrative therapies have been studied for their potential effects on common cold symptoms. Echinacea taken by mouth is frequently recommended to reduce the duration and severity of upper respiratory tract infections. However, the results of scientific studies are mixed. Scientific studies generally suggest that vitamin C does not prevent the onset of cold symptoms. However, in a subset of studies of people living in extreme climates or under extraordinary conditions, including soldiers in subarctic exercises, skiers and marathon runners, vitamin C significantly reduced the risk of developing colds, by approximately 50 percent.

For more information about integrative therapies for the common cold, please visit Natural Standard's Comparative Effectiveness Database.

For more information about zinc, please visit Natural Standard's Foods, Herbs & Supplements Database.

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1. Natural Standard: The Authority on Integrative Medicine. www.naturalstandard.com
2. Science M, Johnstone J, Roth DE, et al. Zinc for the treatment of the common cold: a systematic review and meta-analysis of randomized controlled trials. CMAJ. 2012 May 7.