Should you take zinc for colds?
December 16, 1997
Web posted at: 12:16 a.m. EST (0516 GMT)
(Mayo Health Oasis) -- More and more people are turning to zinc when they feel a cold coming on, but medical experts caution that it is still not clear how well zinc works on colds and how safe it is.
Zinc first gained prominence as a cold remedy with publication of a 1996 Cleveland Clinic study. Study participants who started taking zinc lozenges within 24 hours of the onset of symptoms were free of cold symptoms on average by about 4 1/2 days. Those who took a placebo had symptoms for 7 1/2 days.
Consumers have since voted with their wallets. Zinc lozenges were briefly unavailable due to high demand and several new brands recently have hit the market.
Popularity doesn't equal effectiveness, however. Two preventive medicine specialists at Mayo Clinic, Rochester, Minnesota, agree that zinc shows promise as a cold remedy but caution that it's still unclear just how well zinc works and how safe it is.
Philip T. Hagen, M.D., notes that "there is limited evidence for how to use zinc and even less on how it works, so it makes sense to be cautious in using it. At this point, I would recommend following exactly what was done in the Cleveland Clinic study."
Donald D. Hensrud, M.D., says the Cleveland Clinic study was well-designed and well-conducted: "It built upon previous studies. The results were quite believable."
Consumer awareness is key
If you plan to use zinc to fight cold symptoms, you should keep this advice in mind. "It's a matter of responsibility on the part of the consumer," Hensrud says. "You have to start taking zinc within 24 hours of the onset of symptoms, so you have to recognize them fairly quickly. Doctors seldom see patients for ordinary colds in the first 24 hours. By the time we see them, it's too late to discuss zinc as a treatment -- for that particular cold, anyway."
When it comes to zinc, Hagen cautions against making the assumption that if a little of something is good, a lot must be better.
"Take the lozenges every two hours while awake as in the study and stop taking them when your cold symptoms cease," he says. "I don't think it's good for people to take zinc continuously, at least not until we have better evidence that it does good and not harm." Also, there is no evidence that taking zinc actually prevents catching a cold.
The Cleveland Clinic researchers also noted two side effects of the zinc lozenges. Many participants reported that the lozenges had a bitter or sour taste and most noted at least a mild aftertaste. A few participants disliked the taste so much they discontinued taking the lozenges. More seriously, 20 percent of zinc-takers reported nausea, as opposed to only 4 percent taking the placebo.
"Again, it's a matter of practicality and consumer choice," says Hensrud. "Some people would prefer a longer cold to nausea."
Hagen says some people shouldn't take zinc for colds until it's proven safe for them. These include pregnant women , children and people with chronic kidney disease, liver disease or other serious illness
Long-term, high doses of zinc have also been shown to lower HDL (the "good" cholesterol), to suppress immune system function and to interfere with the absorption of copper which may result in a condition known as microcytic anemia.
This article was excerpted with permission from Mayo Health Oasis, a project of the Mayo Clinic. Visit the Mayo Health Oasis Web site for full text of the story.
1997 Mayo Foundation for Medical Education and Research. All rights reserved. Materials copyrighted by Mayo may be reprinted for personal use only. Permission to reprint or electronically reproduce any document in part or in its entirety for any other reason is expressly prohibited, unless prior written consent is obtained from Mayo. "Mayo Health O@sis," "Mayo," "Mayo Clinic," and the triple-shield Mayo logo are marks of Mayo Foundation and are used under license by Mayo Foundation for Medical Education and Research.
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