GENTECH archive


Independent rebuts Pusztai

     The Independent - London
     Publication Date 2-19-1999

     Steve Connor

     Pusztai: the verdict.
     GM food: safe or unsafe? First we must ask experts in this field how
     they rate the research work that led to this most recent controversy,
     says Steve Connor

     The case of Arpad Pusztai - the scientist forced to retire over his
     public comments about genetically modified (GM) potatoes - has become
     a cause celebre with the environmentalists. He claims to have shown
     that GM food can stunt the growth of laboratory rats, harm brain
     development and damage the immune system. If he is right, it
     represents a hammer-blow to the biotechnology industry, which is keen
     to exploit advances in genetics. If he is wrong, Dr Pusztai could be
     accused of whipping up public hysteria.

     Last week, a group of 20 scientists signed a memo in support of Dr
     Pusztai, stating that the Hungarian-born researcher stands fully
     vindicated. Dr Pusztai's data from experiments he conducted at the
     Rowett Research Institute in Aberdeen clearly show, the memo says,
     that when laboratory rats were fed GM potatoes, their internal organs
     failed to grow fully and their immune systems were suppressed. They
     concluded that Dr Pusztai's research report would be acceptable for
     publication in a peer-reviewed scientific journal.

     It is this last claim that has been put to the test by The
     Independent. Dr Pusztai's report became publicly available this week,
     and we asked one of Britain's leading experts, Professor Tom Sanders
     of King's College London, to comment on whether it would pass muster
     with genuine scientific referees. Professor Sanders concludes (see
     below) that Pusztai's work fails to reach a standard acceptable for a
     peer-reviewed journal.

     Science is only science if it has passed through review by experts
     before being published in a journal. The 20 "experts", mostly from
     abroad, who signed the memo say Pusztai's research is of high quality.
     This is not the view of other scientists who saw it.

     The story began in 1995, when the Scottish Office funded a three- year
     project involving three centres: the Rowett, Durham University and the
     Scottish Crop Research Institute. The aim was to identify ways of
     making crops pest-resistant, with minimium side-effects.

     Dr Pusztai's role, as an expert on toxic plant proteins called
     lectins, was to undertake a series of feeding experiments using GM
     potatoes and laboratory rats. His particular interest was a lectin
     called GNA, found in the bulbs of snowdrops, which acts as a natural
     pesticide. According to Dr Pusztai's report no other lectin-producing
     GM plants were used in the experiments, although he does say he
     performed some "analytical" work with GM potatoes expressing another,
     more toxic lectin, Con A, from the jackbean plant.

     This is a key point because, according to an audit investigation into
     Dr Pusztai's work (ordered by the Rowett following his statements on
     TV's World in Action), he had become confused over whether he was
     talking about GM potatoes expressing GNA or ordinary potatoes which
     had Con A added to them in concentrations 5,000 times greater than
     would occur naturally. The audit, conducted by four scientists, two
     from the Rowett and two from outside, concluded that the only time the
     rats in the Pusztai experiment showed any signs of stunted growth was
     when they were fed Con A in these high concentrations.

     "Therefore, the audit committee is of the opinion that the existing
     data do not support any suggestion that the consumption of rats of
     transgenic potatoes expressing GNA has an effect on the growth, organ
     development or immune function," the audit report stated.

     In answer to this criticism, Dr Pusztai compiled his own "alternative
     report" in which he details what he did and the results he obtained.
     It is this report, which his supporters claim to be of sufficient
     standard for publication in a peer-reviewed journal, which we passed
     to Professor Sanders.

     Dr Pusztai fed the rats a diet of raw, baked or boiled potatoes. Some
     of the potatoes, he says, were genetically modified with the GNA
     lectin and some had GNA added to unmodified potatoes. A diet that
     solely consists of potatoes is so nutritionally poor that he sometimes
     added a protein supplement, otherwise the experiment would breach Home
     Office regulations limiting the suffering of animals. Two types of
     feeding trial took place: one over a 10-day period, the other over 100
     days. His report states there was only one 100-day experiment, where
     extensive protein supplements had to be used. He found the liver
     weights of the animals in this trial actually improved when they were
     fed GM potatoes, and put this down to the protein supplement. Dr
     Pusztai said the long-term trial was only preliminary.

     It was one of the 10 day experiments - code name D242 - where Dr
     Pusztai claims to have observed significant effects which indicate
     that GM food is dangerous. According to Dr Pusztai, rats in this
     experiment were fed GM potatoes, enhanced with the GNA snowdrop
     lectin, as well as ordinary potatoes and potatoes spiked with "free"
     GNA. Dr Pusztai claims the growth of rats was significantly reduced on
     a diet of boiled potatoes, and more so on one of raw potatoes, as
     expected owing to the low nutritional value of potatoes compared with
     a high protein diet.

     "However, in this instance the difference between the final body
     weight and empty body weight of rats (accounting for food in the gut
     lumen) which were fed raw, transgenic potato diets as significantly
     higher than that of rats given diets containing the raw parent line.
     This again indicated that digestion and absorption of nutrients of
     transgenic potato diets was retarded in comparison with ordinary
     potato diets," Dr Pusztai writes.

     A test of the rats' immune systems during this experiment also
     indicated that the animals fed transgenic potatoes were almost always
     more suppressed. Dr Pusztai claims that when free GNA was added to a
     diet of unmodified potatoes, he did not see this suppression. In other
     words, there was something about the act of genetic modification
     itself that has led to the effect he has observed. Environmentalists
     jumped on this as evidence that all GM food is unsafe.

     Dr Pusztai's conclusions were unambiguous: "Four feeding trials were
     carried out ... In all four experiments, feeding transgenic potatoes to
     rats induced major and in most instances highly significant changes in
     the weights of some or most of their vital organs ... The growth rate
     of rats fed potato diets was slightly but significantly less than that
     of rats fed a high-quality control diet, but the presence of GNA,
     whether added to potato-based diets or expressed in the transgenic
     {plant} had no significant effect on weight gain and weight change
     compared to parent potato lines."

     Dr Pusztai's two outside collaborators at the Scottish Crop Research
     Institute and the University of Durham have distanced themselves from
     his conclusions. John Gatehouse, at Durham, is understood to be
     privately furious at Dr Pusztai's failure "to consider the most
     elementary tenet of science - that before one reaches a conclusion
     about cause and effect, it is necessary to demonstrate that causality

     Meanwhile, the four members of the original audit committee have
     looked at Dr Pusztai's alternative report and found that it is not

     Dr Pusztai may have convinced the 20 scientists who signed the memo,
     and certain sections of the media, but he has failed to win over the
     experts - including his own colleagues - who are closest to the

     Tom Sanders, professor of nutrition at King's College London, is one
     of the most distinguished food toxicologists in Britain. He is a
     member of the Government's Advisory Committee on Novel Foods and
     Processes, and has acted as an expert reviewer for some of the leading
     scientific journals in the field. This is an edited version of his
     peer review of Dr Arpad Pusztai's "alternative report", which
     environmentalists have used to support a ban on genetically modified

     "THIS DOCUMENT reports four feeding studies with transgenic potatoes.
     The document has not been carefully prepared and is not up to the
     standard required for publication in a good scientific journal. The
     tables are not clear, and the captions do not make it clear whether the
     results are expressed as mean with SEM or SD {two statistical ways of
     expressing the possible error in calculating an average}.

     "The food intakes are not adequately described - this data is
     essential for interpretation of the data. The dietary design of the
     first three studies is fundamentally flawed, as the diets did not
     contain adequate amounts of protein and the intake of nutrients and
     antinutrients differed between the transgenic and control animals.

     "An intake of 100g protein/kg diet is regarded as the minimum amount
     for growing rats, and results in some degree of malnutrition,
     particularly when under stress such as pregnancy. Most commercial rat
     diets contain protein at 200g/kg diet to support normal growth. The
     first three studies use between 55.6 and 72.5g protein/kg. This level
     of protein was not adequate to sustain normal growth and development
     in the rats. The transgenic potatoes contained 20 per cent less
     protein than the parent variety but it appears no attempt was made to
     ensure that the protein content of the diets was similar. Thus
     differences between the parent variety and the transgenic animals
     could be attributed to differences in protein intake.

     "It is unclear why a diet of raw potatoes was used, given that they
     are renowned for containing high levels of natural toxins. The study
     generalises conclusions made from the use of raw potatoes to the use
     cooked potatoes.

     "It is well documented that protein malnutrition in rats leads to
     decreased growth rate, changes in gut morphology and hepatic atrophy
     features that were observed in these studies. The report gives the
     impression that these dietary aspects of the study were considered
     post hoc. Why were the potatoes not analysed before the diets were
     formulated? And why was the lower protein content in the transgenic
     line not compensated for by additional protein?"

     Professor Sanders casts doubt on the statistical analysis that led Dr
     Pusztai to conclude that the brains of rats fed GM potatoes were
     affected by their diet. "It is odd that differences in brain weight
     were reported, as brain weight is generally not influenced by diet in
     adult rats," he says. "The statistical analyses is muddled. The tables
     do not indicate the number of animals in each group is not given. ...
     Many of the reported differences are not significant.

     "I would not recommend this paper be accepted for publication in its
     current form. In my experience as an editor and reviewer it would be
     rejected by the British Journal of Nutrition, Journal of Nutrition and
     American Journal of Clinical Nutrition. Although the report is of poor
     quality, the subject matter is novel so I would not to reject it
     outright even though the first three studies are fundamentally flawed
     in their design (deficient in protein). I would invite the author to
     respond to detailed criticisms and consider a revised version with
     more detail and suggest further studies, particularly with regard to
     the lymphocyte proliferation studies {a test of the immune system},
     which are unconvincing."

     (Copyright 1999 Newspaper Publishing PLC)

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