Some years ago George Eby noted that using zinc gluconate lozenges apparently benefited his daughter's colds, so he organized a clinical trial to test the idea. The results showed that such treatment improved the outcome. Although the trial did have some faults, we conducted a further test of his formulation in volunteers given experimental colds at the Common Cold Unit at Salisbury. The results of the test seemed to show benefit if the lozenges were given before or during the cold, yet similar studies at the excellent unit at the University of Virginia failed to confirm our findings.

Mr. Eby has taken expert advice and investigated the possibility that it isn't merely the presence of zinc in the lozenge which matters, but the amount and duration of the Zn²⁺ ions released that determines whether there is an effect or not. He has combined his own studies of the characteristics of the formulations used with the published results of trials in a type of meta-analysis. It is not possible to present the amount of benefit in formally the same terms, but the results do support his case that the differences might be due to the release characteristics of the Zn²⁺ ions.

Of course this doesn't settle the problem. It has been suggested that our trials failed to control adequately for the volunteers guessing whether they had active or placebo lozenges, and so produced a spurious positive result. There is also the problem that there is no evidence that Zn²⁺ ions actually reach the infected mucous membranes in the nose; however, in a sense that does not matter as there are many examples of active treatments being discovered when there was no evidence of how they worked.

It is therefore worthwhile keeping the debate open in spite of the negative results in some trials and other much less plausible claims for benefits from zinc. This book helps in that debate by bringing together summaries of the biology of zinc, the results of the trials in common colds and the results of the analyses of the formulations used. The texts of original papers are also there to help the careful reader.

I welcome this book. The best result of its publication would be at least one vigorous trial using zinc lozenges formulated with precisely the characteristics of those used and recommended by Mr. Eby, and with vigorous monitoring of the double-blind precautions and the clinical course of the patients.

David A. J. Tyrrell, M.D.,
retired Director Common Cold Unit
British Medical Research Council,
Salisbury (UK)

and currently with the:
British Medical Research Council
AIDS Directed Programme Public Health Laboratory Service
Centre for Applied Microbiology and Research
Porton Down, Salisbury, UK

In 1994, there continues to be a debate as to the efficacy of zinc in the prevention and/or treatment of the common cold. The initial studies conducted by Eby et al (1984) did suggest some efficacy although the trials were not perhaps as vigorously controlled as they should have been. We conducted double blind placebo-controlled studies at the MRC Common Cold Unit in Salisbury and found some benefit if the lozenges were given just before or after the onset of colds. One of the main criticisms of our trials was that there was not a sufficient number of volunteers in the second phase of the study which was the treatment with zinc lozenges. Studies in the USA and Australia however, failed to confirm these findings. This book attempts to review the role of zinc lozenges in the prevention and treatment of the common cold and summarizes the biology of zinc. I, like David Tyrrell, therefore welcome this book and hope that it would continue to debate the subject further with the hope that it may encourage further controlled trials.

Widad Al-Nakib, MA FRCPath PhD
Principal Investigator, Common cold Unit
British Medical Research Council CCU
currently at Advanced Pathology Services
London UK