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Are there scientific support for gecko powder as an anti cancer remedy?

December 21, 2010

My recent blog on the use of tockay (tokay) gecko as an anti cancer remedy resulted in increased reading frequency and remarks from supporters of gecko medicine.

I got a reference to a publication which may seem to confirm the use of dried gecko powder as an effective anti cancer remedy. Since we at Dokmai Garden believe it is essential to promote knowledge and scientifically based arguments, we suggest anyone interested in this matter download the article (http://www.wjgnet.com/1007-9327/14/3990.asp) and then consider the questions I raise below.

Bear in mind I am not a medical doctor, but as an associate professor in forest microbiology and an experienced peer reviewer for numerous scientific journals, I can judge experimental design. I simply raise questions to help an editor judging a study, and helping the authors to improve their study. Occasionally, I have rejected manuscripts which have resulted in the same manuscript showing up in less esteemed journals.

If I had been the reviewer, I should have told the editor that “the authors have addressed an important question and selected sound methods for a preliminary pilot study proceeding large clinical trials. However, the authors need to expand their sampling, include or state concentrations corresponding with actual treatment doses and improve the controls, in order to present more convincing data or reject the hypothesis”.

The major problems with the article are

Dose

I should have appreciated a statement about how much gecko powder is generally administered to a patient per day. I fear the authors focused on too high concentrations (equivalent to 3-10 fresh tockays a day/person), perhaps omitting results from lower concentrations?

In most biological studies, one uses tenfold differences to make sure there are no doubts in efficiency. According to page 3992 (in vivo study) the authors used 4.5, 9 and 13.5 g gecko powder/kg mouse body weight. Since an average lab mouse weighs about 20 g or 0.02 kg, the highest dose was 0.27 g/mouse, equivalent of 1080 g of dried tockay gecko for an 80 kg person.  A large living tockay gecko weighs 300 g, when dried ca 100 g (70% water). The largest dose proposed was equivalent of eating ten large fresh tockay geckos per day. That is actually good for experimental reasons, since it is probably much higher than actual doses. To see an effect without doubt, one has to select a level where there has to be an effect, if actually existing. Instead of using the authors’ series equivalent of ten, six and three fresh tockay geckos per person/day, where all doses are surprisingly high, one should have selected the series of 15, 1.5, 0.15 and 0.015 g dried tockay powder/kg body weight a day (roughly equivalent to ten, one, a tenth and a hundredth of a fresh tockay gecko per day).

Controls

I conclude the controls were poorly designed. To exclude the possibility there was a general decline in laboratory cell growth due to any kind of dried meat (see results in Figure 1), the authors should have compared with other dried foods, such as dried chicken powder. If there had been no significant difference between chicken and gecko, then there would be no reason to specifically hunt for gecko. In the in vivo study (page 3992 and table 2), the negative control got an injection but no food and no forced feeding, but the treatment group got food (gecko) by forced feeding, but no injection. One can not outrule the possibility the experiment accidentally evaluated differences in immunological response between accustomed food (mouse pellets) and new food (gecko powder) through forced feeding. A negative control has to be identical with the treatment group, except for the one parameter being studied. In this case three additional factors (injection, handling, food) differed.

Statistics

The number of mice, ten for each treatment, was not sufficient as the SD values indicated a very high range in measurements (Table 1-2, 72 hrs). Measured values of the control group (i.e. not the average) overlapped with values of the treatment groups. I did not see any dose correlation in the in vivo experiment (Table 3). I only saw significant response in the chemical treatment.

Other facts to consider are

Journal

The article was published in the journal World Journal of Gastroenterology which is Chinese. It has an impact factor of 2, which means that on the average each article is cited twice by other scientists. In comparison, the journal Gastroenterology has an impact of 13, i.e. it is considered a much more reliable journal by other scientists. The Chinese journal charges money for publications. If this study truly showed an alternative to chemical tumour treatments, why did not the authors publish in a more prestigious journal? We can not outrule that they initially tried, but were rejected due to the weaknesses I mentioned above. A pioneering discovery can of course be published in a marginal journal, but one has to be more careful when reading such journals as the editor may not have access to the best peer-reviewers.

University

The authors are Chinese, active at University of Henan or affiliated Henan institutes. This university is not even among the top 500 universities in the world, according to the Chinese ARWU 2010 which ranks universities specialised in natural sciences. This may not be a problem, but a publication from a university among the top 100 is usually more trustworthy due to their tradition of accuracy, and the reader can feel more confident.

References

In the second paragraph of the introduction it is stated that gecko can restrain allergies and inflammations. This is probably the anecdotal background, summarized in reference 5, which was impossible to download. The authors go on stating gecko has been used to cure tuberculosis and bone inflammations, and that it has a “definite effect against malignant tumours”, citing articles 6-8. I could not open articles 6-7 and article 8 is in Chinese which I can not read. This does not necessarily mean the reports are wrong, it simply means non-Chinese are unable to evaluate the statement.

I would have liked a reference to any other scientific study indicating that there are other non-venomous reptiles being a source of a generally accepted medicine. I am not aware of any such medicine on Earth.

Discussion

There is no hypothesis presented to explain a biochemical mechanism, i.e. an explanation what unique compound(s) inside the gecko would decrease tumour growth. The authors are satisfied in believing they confirmed the folklore, forgetting a very important control (other dried meat), emphasizing measurements from a small sample without commenting on the SD values and using extremely high levels of gecko powder. It is also dangerous to transfer the results based on one species (Gekko japonicus) to another species (Gekko gecko, the tockay). Since the authors do not know what compound(s) inside G. japonicus is interesting, why would Chinese tockay importers assume compound(s) x exists in all geckos?

Only one article

Even if there had been convincing results in the article at hand (there were not), other scientists must be able to repeat such results before one can actually trust a new medicine. One article is not enough, several independent groups must come to the same conclusion. The reason is that somebody making big money on tockay trade, may order a study with a given result. Asking scientists to prove a hypothesis rather than testing a hypothesis was very common during the Stalinist era in the former Soviet Union, which is why decades of biological research in the Soviet Union are dismissed as unscientific. In the end, only clinical studies on patients, using large numbers, would give a decisive answer.

Folklore vs science

I wish to emphasize that I do believe that a lot of advice can be brought from traditional Chinese medicine, and pharmacognosy is a most important research field. However, it is also very important we evaluate each alternative medicine by studying its effects by measurements rather than believing in anecdotes. We have to use good negative and positive controls, and also use sound statistics so that we are not fooled by seemingly exciting measurements. Some people seem to swallow any folklore as long as it involves Chinese medicine. Since the life expectancy in North America (USA 78 years, 2008) and western Europe (Sweden 81 years, 2008) is higher than the official life expectancy in China (73 years, 2008), a scientific approach to medicine seems to work. This is even more striking if we go back to 1960, when the Swedish life expectancy was 73 years and the Chinese was 46.6 years. In addition to starvation, at that time most Chinese had only access to their traditional medicine. Romantic and innocent belief may kill you, or the tockays.

Spiny tailed house gecko boy (Hemidactylus frenatus) courting with his fiancée.

Read about Dokmai Garden’s efforts in saving Thai orchids.

Text and Photo: Eric Danell

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2 Comments leave one →
  1. Don permalink
    December 22, 2010 7:52 AM

    very authoritative review, thanks

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