GM Science Review - Comments on First Report

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Name: Derek Burke Location (optional): Date: 13 October 2003
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Professor Derek Burke CBE DL

Dear Dr Butt,

I wish to comment briefly on three sections of Dr. Pusztai's letter of July 31st:

  • His implied accusation of my own incompetence.
  • His defense of his own work.
  • His criticism of some data supporting the conclusion of the lack of any adverse effect on animals which had been fed GM foods.

One of Dr Pusztai's remarks which warrants particular rejection is: "In this context one can also ask that since when the opinion of a former scientist (Dr Burke) carries such weight that on his word and without experimental evidence the results of a peer reviewed paper on GM potatoes are rejected because a Chinese scientist had done some work on GM tomatoes and sweet peppers even though this has never been published?"

1. The phrase "a former scientist (Dr Burke)". I do not need to defend my scientific credentials; they can be found in any recent edition of 'Who's Who' or 'People of Today'. But briefly, I was appointed in 1969 as Professor of Biological Sciences at the University of Warwick and founding Chairman of the new Department of Biological Sciences, a Department has since scored at the highest grade in every Research Assessment Exercise. While I was there I cloned the interferon genes and isolated the first monoclonal antibody to interferon (Celltech's first product), and published a number of papers in prestigious journals, including PNAS, Cell, and Nature. I have over 130 publications, mostly in peer reviewed journals. Later, while working in Canada, I was appointed a Professor at McMaster University, and subsequently also at the University of East Anglia; colleagues will know that all such appointments involve peer review. I am now an Emeritus Professor and have two honorary Doctor of Science degrees. Moreover, I have worked on peer review and science policy for the Medical Research Council, the Cancer Research Campaign, and the BBSRC. I was a member of the Technology Foresight Steering Group, and Editor and Editor in Chief of the Journal of General Virology. In that latter position, I personally read, edited, and checked referees' comments on every paper we published - about 200 papers per year over four years. I consider that I have the credentials to make a judgment on other people's work, and do not need to answer to Dr Pusztai or anybody else.

2. A full account of the claims Dr Pusztai makes for his own work and the subsequent events can be found in Appendix 1 of "Genetically Modified Crops: the ethical and social issues" pages 140 - 142 ( Dr Pusztai first made his claims that feeding GM potatoes to rats produced damage to the immune system on television on August 10th, 1998 and then in a series of press releases, but it was not made clear then or later that this work was part of a tripartite collaboration, the genetic constructs having been made at the University of Newcastle, and the GM potatoes grown at the Scottish Crop Research Institute. Only the feeding experiments were done in Dr Pusztai's laboratory. Because of the controversy his claims aroused, an independent audit committee reviewed his results and the outcome was published on the Rowett web site on the 28th of October, 1998. The report made four substantial criticisms of the work, and in addition, pointed out three ways in which the claims made on television conflicted with his data. Dr Pusztai rejected some of the conclusions of the audit committee, but the committee was not persuaded by his response to alter their conclusion.

Then on 12th of February 1999, scientists from fourteen countries (at least one of whom rapidly withdrew) announced their support for Dr Pusztai in a Press Conference at the House of Commons. In an accompanying Greenpeace press release, the possibility was raised that the damage claimed to by Dr Pusztai might be due to the virus that was used as the source of the promoter in the transgene constructs. On February 19th a full review by the Royal Society was announced and this was published in June, 1999 with the title "Review of data on possible toxicity of GM potatoes" ( It concluded that the reported work from the "Rowett [Institute] is flawed in many aspects of design, execution and analysis and that no conclusions should be drawn from it." Further: "We found no convincing evidence of adverse effects from GM potatoes. Where the data seemed to show slight differences between rats fed predominantly on GM and on non-GM potatoes, the differences were uninterpretable because of the technical limitations of the experiments and the incorrect use of statistical tests. The work concerned one particular species of animal, when fed with one particular product modified by the insertion of one particular gene by one particular method. However skillfully the experiments were done, it would be unjustifiable to draw from them general conclusions about whether the genetically modified foods are harmful to human beings or not. Each GM food must be assessed individually." Dr Pusztai's data was not published until later in 1999 (Ewans S W B & Pusztai A, (1999) The Lancet 354, 1353-1354). It's claims were criticised by both the Royal Society and the BBSRC.

3. Dr Pusztai writes very critically of some of the results reported in the review which Professor Michael Gasson (currently acting Director of the Institute of Food Research, Norwich) and I wrote after an invitation from Nature, which after peer review, was published in Nature Reviews Genetics, 202, March 2001 pp.217- 222, with the title "Scientific perspectives on regulating the safety of genetically modified foods". This was a detailed review of the scientific issues that have arisen over the years to in the process of regulation. In passing, in one sentence, we referred to work carried out by Professor Z-L. Chen and nine colleagues in China, in an attempt to repeat Dr Pusztai's claims. Professor Chen's paper, which was unpublished at the time of writing but was sent to me by him, and which has now been published in Plant Journal, is very detailed, running to eleven pages of text, six very detailed tables and six figures. The summary includes the statement "The results showed that no significant difference was found in growth, accumulative body weight gain, food consumption, haematology, blood biochemical indexes, organ coefficient and pathological evaluation between rats and mice of either sex fed with GM diets and those with non-GM diets. It was also found that GM products had no mutagenic activity either in vitro or in vivo by micronucleus test, sperm aberration and Ames test. These results suggest that the GM sweet pepper and tomato are comparable to the non-GM counterparts in terms of safety as food."

The Chinese work is, of course, not the only feeding study that has been done; a very large number of feeding studies have been carried out with the paste from GM tomatoes and with GM soya and no adverse effects have been found. No reputable scientist I know believes that Dr Pusztai's conclusions are general for the products of GM crops. The explanation for the effects he reported remains obscure, but they have neither been able to be repeated, nor are they supported by his own former institute, nor by an independent audit committee nor by a specially convened Royal Society Working Group. I believe they should firmly be set aside.

Derek Burke
October 13th, 2003