• Zinc for colds

    A couple of years ago, Rachel Vreeman and I wrote a paper on medical myths, which led to another paper on medical myths, which led to a book on medical myths. Go buy it! There are links over there on the left. A sequel is coming out this summer, so you can expect more begging then.

    Because of this, we get asked about stuff pertaining to medical myths all the time. For instance, I’m filming a TV show this afternoon (more on that when it gets close to air). Today, this came out on zinc and colds:

    Studies have been all over the map on the benefits of zinc as a cold-fighter. Back in 1999, a Cochrane review found little evidence that zinc helps reduce the misery of the common cold. This new review evaluated almost twice as many randomized, placebo-controlled studies as the 1999 effort – 15 compared to 8.

    It found that over-the-counter products with zinc did reduce the severity and duration of people’s cold symptoms overall, particularly if they started taking zinc within 24 hours of feeling symptoms. Two of the studies also found a reduction in the number of colds that people had

    “There was reduced use of antibiotics in those who used zinc,” says Kay Dickersin, a professor of epidemiology at Johns Hopkins Bloomberg School of Public Health, who directs the U.S. Cochrane Center. That’s good, Dickersin says, because antibiotics are generally overused, and are useless against the viruses that cause colds.

    It just so happens that USA Today was planning a piece on cold treatments (spoiler – they don’t work). They had interviewed us for that piece, and when the press release on the new zinc study came out, they went into a panic. Luckily, Rachel was ready to chat with them:

    Although the review suggests that these zinc products might also make cold symptoms less severe, Vreeman notes that the quality of the studies wasn’t very strong — suggesting that future research could come up with a different conclusion.

    “One of the big challenges with this research is that they have a hard time making a placebo that people actually believe in,” Vreeman says. “The bad taste of zinc, and the fact that it often makes people feel nauseous, are common, and tend to make it clear who is getting the zinc and who is getting the placebo.”

    Vreeman notes that many people may decide that the treatment is worse than putting up with a cold for one more day.

    Some forms of zinc also pose serious risks.

    The Food and Drug Administration in 2009 warned consumers not to use any intranasal zinc products because of concerns that it can make people lose their sense of smell.

    It’s also worth remembering this (emphasis mine):

    If you’re considering zinc products as a cold remedy, start taking zinc as soon as possible after cold symptoms first appear. Study participants reported the most benefit when they took zinc medications within 24 hours of a cold’s onset. People had to take zinc regularly for at least five months for zinc to have any benefit in reducing the number of colds.

    Because the studies used many different dosages and forms of zinc, the Cochrane reviewers said they weren’t able to recommend a dose. But earlier studies have found that more is usually better. Alas, more zinc can cause unpleasant side effects, including nausea and bad taste, diarrhea, abdominal pain, and dry mouth.

    Being the research-loving duo we are, we’re revising the sequel in gallies in order to include this new information. Yes, there is now statistically significant evidence (whose strength is debatable) that zinc may help.

    But if you’re asking me if I will be taking zinc if I get a cold, the answer is no.

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