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Zinc Lozenges for the Common Cold

 
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Zinc lozenges are available in a variety of formulations to treat the common cold. They remain somewhat controversial. The main questions are: Do they work? If so, does zinc boost the immune system or attack the viruses directly? What is the effective dose? And is it safe to consume this much zinc?

It's important to know the mechanism(s) of action because if zinc kills the virus directly, then it makes sense to use zinc lozenges and/or nasal sprays. If immune support is the only effect, then a simple pill might be just as effective.

Safety was demonstrated in a clinical trial of Cold-Eeze in people 60 to 91 years old. The study participants took one of these lozenges or a placebo every 3 to 4 hours for 6 days. The researchers assessed both groups for health effects at baseline, 7 days, and 14 days. They found Cold-Eeze to be as safe as placebo.

For effectiveness, different researchers report different results. Part of this variation comes from the difference in dosage and lozenge formulation: zinc acetate, zinc gluconate, zinc orotate, and other forms have been tested.

One of the most promising clinical trials I found was conducted at Wayne State University. The researchers prepared zinc lozenges and placebos with the same look and taste. Tests on healthy volunteers confirmed that the placebos were indistinguishable from the test lozenges, which contained 42.96 mg of zinc acetate dihydrate (12.8 mg of zinc). Fifty volunteers with colds were randomized to zinc or placebo. Volunteers dissolved one lozenge in their mouths every 2 to 4 hours while awake, as long as they had cold symptoms. The researchers measured levels of three proinflammatory cytokines to see how the zinc affected the immune system. Volunteers reported their cold symptoms on a daily log.

Zinc was highly successful in this trial: the average duration of cold symptoms was 4.5 days in the zinc group, and 8.1 days in the placebo group. For individual symptoms, zinc had the most effect on cough: average 3.1 days in the zinc group, and 6.3 days in the placebo group.

The mechanism for zinc's benefits was not established. The authors conclude that both immune system changes and antiviral effects could be contributors.

References:

Prasad AS et al, “Duration of symptoms and plasma cytokine levels in patients with the common cold treated with zinc acetate: A randomized, double-blind, placebo-controlled trial”, Annals of Internal Medicine 2000:133:245-252.

Silk R et al, “Safety of zinc gluconate glycine (Cold-Eeze) in a geriatric population: a randomized, placebo-controlled, double-blind trial”, Am J Ther. 2005 Nov-Dec;12(6):612-7.

Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.

Add a Comment3 Comments

Some researchers speculate that most of us get tired of sucking on lozenges before we get enough to make a big difference. But compared to colds? I can deal with lozenges!

December 7, 2009 - 9:14am

Linda,

Thanks so much for this post. I have wondered also whether it was primarily a marketing angle or whether zinc offered true relief. There is a very popular line of zinc lozenges on the market that I've tried several times. Sometimes I thought it might have made a difference and other times I was pretty sure it didn't. (It's the old saying: My cold lasted 7 days with the lozenges, a week without them, LOL.) So I was interested to read the science behind it. Thank you.

December 7, 2009 - 8:04am
Expert HERWriter Guide Blogger

Hi Linda - I've been curious as to whether zinc is effective, and appreciate the information you've provided. The clinical trial results are quite impressive. Colds can make one really miserable - thanks for bringing this to our attention as we head into the winter cold season.
Take good care,
Pat

December 4, 2009 - 6:37pm
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