As a follow up to my vitamin C bombing post I decided to talk about another common "natural" cold remedy that usually starts circulating about this time--zinc lozenges, most often sold under the brand name Cold-Eeze. In doing the research, however, I found that Dr. Steven Salzberg has already done at least three excellent reviews within the past year, and he tells us what the evidence has to say.
The first article was published back in March of 2012 here. Apparently there is some evidence that zinc can actually reduce the length of the cold--by a whole one day. If I'm having general ickyness for seven days or six days--it's probably not enough to make me spend the money on zinc losenges, especially since the reduction in symptoms is usually so gradual. And then there is that possibility of losing the sense of smell, permanently that I didn't like either. Why take that risk if it isn't even going to help my symptoms? It looks like Dr. Salzberg came to the same conclusion as well.
Two months later, Dr. Salzberg commented on this again here. I liked that he pointed out two major red flags that one needs to look for when evaluating studies. One, the studies that came out in favor of the zinc lozenges were all funded by the industry--so the potential for confirmation bias was quite high. Two, it looks like they were using those notoriously unreliable self reporting questionnaires again; one of the reasons why the decrease in cold symptoms was different for children as oppossed to adults might be that adults might be more likely to tell the researchers what they want to hear. Once again, I wouldn't want to spend my money on something that doesn't really reduce my symptoms based on what appears to be a sophisticated advertising campaign.
And my favorite article from Dr. Salzberg was posted in July of this year. He once again points out that most of the studies reviewed were funded by the industry, demonstrates that we need to look at more recent studies that invalidate the claims of earlier studies, discusses the value of going back to the original studies and figuring out whether they were published in peer reviewed journals, and also discusses the logical fallacy of special pleading. This happens to be one of the most amusing logical fallacies to me for some reason, it essentially says zinc losenges will not work for me because I am a skeptic (in other words, I don't believe in zinc so it won't work).
Take home message--unless you feel like spending money, if you have a cold you can do other things like drink hot tea and eat chicken soup to ease the pain, but zinc lozenges most likely won't help you.