Zinc – “Clinically proven”

Whether stated in an ad for conventional or alternative medicine, I typically take claims of “clinically proven” with a grain of salt. That’s because the statistical methodology used to “prove” these claims basically says “if we assume these claims aren’t true, then the results we have seen in studies would have been too bizarre.” This is even though advertisement language is regulated by the DSHEA(Dietary Supplement Health Education Act?), Food, Drug and Cosmetic Act, the Code of Federal Regulations Title 21 Part 101, and so forth. So, when I saw the words “clinically proven to cut your cold nearly in half” by the Cold-Eeze® product manufactured by the “Quigley Corporation”:http://www.quigleyco.com, I naturally got a bit curious.

Cold-Eeze is the homeopathic remedy Zincum Gluconicum along with inactive ingredients. The form I saw was a lozenge, and the dilution was 2X (i.e. a factor of 10^2^=100). The back of the box makes the following claim:

Two clinical studies have shown: Cold-Eeze proprietary formula reduces the duration and severity of cols by 42% or 3 to 4 days.

The independent double blind studies were conducted at the Cleveland clinic and Dartmouth College and published in peer-reviewed journals.

The two articles are as follows:
* Mossad, _et al._ ??Annals of Internal Medicine??. *126*:2, July 15, 1996. (“PubMed”:http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=8678384&query_hl=1&itool=pubmed_docsum | “Full Text – free”:http://www.annals.org/cgi/content/full/125/2/81)
* Godfrey, _et al._ ??Journal of International Medicine Research??. *20*:3, June 1992. (“PubMed”:http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=pubmed&cmd=Retrieve&dopt=AbstractPlus&list_uids=1397668&query_hl=3&itool=pubmed_docsum)

I don’t know that much about ??JIMR(Journal of International Medicine Research)??, but the ??AIM(Annals of Internal Medicine)?? is certainly one of the top-tier publications. (This means little in my book, but hey, we’re talking about one of the topics that James Randi has staked his $1 million prize on from my understanding.)

So, the Mossad article in ??AIM(Annals of Internal Medicine)?? does show a well-designed and well-controlled study of zincum gluconicum in which the severity of symptoms was reduced from a median of 7.6 days in the placebo group to a median of 4.4 days in the zincum gluconicum group. The full text is available, and this study makes it look like this formulation does reduce duration of symptoms. Do read the discussion section of the article to see the limitations of the study. No mention was made of the method of preparation of the active ingredient (i.e. dilution), and the discussion of mechanism was phrased in terms of clinical pharmacology rather than homeopathy. This may reflect a bias in the journal or the authors, or Quigley may have produced non-homeopathic zinc lozenges for the study. It’s also worth noting that on the box the company states that the active ingredient is a homeopathic cold remedy, but I didn’t see a mention of the Homeopathic Pharmacopoeia of the US.

The Godfrey article is not in full text online, but from the abstract it looks like zinc took 1.2 days or 4.9 days off the duration of symptoms, depending on when therapy was started. The formulation and treatment schedules were not discussed.

So, it does look like the Cold-Eeze product performed pretty well in those two studies, if in fact is was a similar formulation. However, what about other studies? Some seem to be more negative on zinc:
* Eby, GA and Halcomb, WW. ??Altern Ther Health Med.?? 2006 Jan-Feb;12(1):34-8. “We found no reason to recommend intranasal zinc gluconate or zinc orotate lozenges in treating common colds.” The measured number of patients free of symptoms after 7 days, and 10/16 (63%) in the zinc group compared with 9/17 (53%) in the placebo group. I actually find their conclusions bizarre in light of their sample size and measure. If they had wanted to detect a 20% difference between placebo and zinc, the study would have had 20% power. It’s pretty awful to have an underpowered study and then claim no difference when you can’t reject the null hypothesis. Heck, if we were allowed to do that, I could make it look like penicillin was ineffective. So I’d take the numbers from that study as a bit of information, but ignore the conclusions.
* Wintergerst, ES, _et al._ ??Ann Nutr Metab.?? 2006;50(2):85-94. Epub 2005 Dec 21. This is a review of done on zinc and vitamin C, basically as nutrients. The article does note that adequate amounts of zinc and vitamin C seem to shorten duration of symptoms.
* Arroll, B. ??Respir Med. 2005 Dec;99(12):1477-84.?? This Cochrane database review notes that zinc does seem to have some efficacy, and might be useful.

There are many others. A “PubMed search”:http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?CMD=search&DB=pubmed of “zinc treatment cold” (no quotes) returns 192 articles. Sorting through these studies and accounting for differences in formulation, dosing schedule, actual dose, delivery, and other factors that greatly affect drug efficacy is dizzying and daunting at best. It’s also important to remember that zinc lozenges do carry the potential for adverse events, such as bad taste and nausea.

Also not discussed in these articles are the issues of homeopathic dilution of zinc compounds. This is going to be hard to find because of the bias of journals, and because I still haven’t seen evidence that zinc is in the HPUS.

Finally, the long-term consequences of the suppression of common cold symptoms has not been discussed. Zinc has no effect on virus-shedding, so presumably it doesn’t help the body dump the cause of cold any faster. Whether reducing the severity of symptoms is, in the long run, useful, has not been answered.

For me, the jury is out on zinc as a cold remedy. It seems to do something. Exactly what, I want to understand a little bit better.

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