Submission of Dr Árpád Pusztai

In this submission the emphasis has been placed on the potential human/animal health aspects of genetically modified, GM, food. It is based on the results of our nutritional, toxicological and immunological studies with rats fed on diets containing two different samples of GM potatoes expressing the gene of the snowdrop bulb (Galanthus nivalis) lectin, GNA. What makes this study exceptional is that it was one of the very few studies which had not been industrially funded but publicly financed by a major grant from the Scottish Office Agriculture, Environment and Fisheries Department (SOAEFD). A part of these findings had also been published in a peer-reviewed scientific journal (1). Although our pioneering experimental work was interrupted and stopped after 33 months, the results were serious enough to sound a general warning to the public (who after all financed our project) about the possible health dangers of GM food. This I did in August 1998 in a short (150 sec) TV interview given with the full consent of the Director of the Institute (Rowett Research Institute, Bucksburn, Aberdeen, Scotland UK) because our concern became particularly acute with the realisation that whereas the GM potatoes we tested and found to have adverse effects on the metabolism, organ development and the immune system of young, rapidly growing rats had not been approved for human/animal consumption by the regulatory authorities, the British public had been eating GM soya, maize and tomatoes for nearly two years with their full approval even though these had not been as rigorously tested as our GM potatoes.

As our GM potato nutritional trials were one of the very few independent works carried out to date, it is thought to be instructive to describe the background to the project, the results and conclusions reached and the potential consequences of our studies in some detail, particularly as these can then be used in a more general context about the need for safety testing of GM foodstuffs.


In 1995 SOAEFD commissioned a 3-year multicentre project: Genetic engineering of crop plants for resistance to insect and nematode pests: effects of transgene expression on animal nutrition and the environment. The main objective of the programme was: "To identify genes encoding antinutritional factors which will be suitable for transfer into plants to enhance their resistance towards insect and nematode pests, but will have minimum impact on non-target, beneficial organisms, the environment, livestock fed on these plants, and which will present no health risks for humans either directly or indirectly through the food chain ". The call for research proposals by SOAEFD in 1995 was in recognition that research into some aspects of genetic modification of crop plants, such as their effects on the environment is a new area of research of fundamental importance and particularly that their dietary use and possible impact on the mammalian gastrointestinal tract has been a neglected research area without a single published paper at the time (1995). Even now 6 years later there are only about half-a-dozen papers published on the health aspects of GM food in peer-reviewed scientific journals. Our proposal describing in detail the genes and plants we were to use, the experimental designs and protocols, the tasks of each participant and the milestones of the research programme was peer-reviewed by BBSRC and approved by leading scientists in the field. In recognition of its outstanding merits, particularly as the programme of work contained extensive feeding trials of GM food plants with rats, SOAEFD selected our proposal against stiff competition by over 20 other European groups. The genes considered for transfer in our proposal were those coding for plant antinutrients including lectins. Thus, with our extensive and almost unique previous experience of feeding studies with rats using diets rich in these natural insecticidal factors, it was decided that the programme of collaborative work which included wide-ranging studies on the effects of GM-plants on the environment, target pests, beneficial insects and soil bacteria at the Department of Biology, University of Durham (UD) and the Scottish Crop Research Institute (SCRI) should be best coordinated from the Rowett Research Institute (RRI). One of the most important work tasks was that, based on the results obtained during the three-year study, we should establish novel methods for testing the safety for mammalian consumers of GM-potatoes and to make recommendations to the regulatory authorities for the testing and risk assessment of other GM-crops to be used in foodstuffs. Our work at RRI has concentrated on tubers from GM-potato lines expressing the gene of snowdrop (Galanthus nivalis) bulb lectin, GNA. The selection of this lectin gene was not arbitrary but preceded by 6 years of previous work at RRI in which we demonstrated that GNA, even at much higher levels of dietary inclusion (up to 42 mg GNA/rat/d) than the expected expression levels in GM-plants, had apparently no appreciably deleterious effect on the growth and health of young rats (2,3). Additionally, this gene has already been incorporated into several crops (rice, cabbages, oilseed-rape, etc) and indeed GNA-GM-potatoes have been grown in field-trials for several years in the UK.


  1. The results of chemical analyses of two GM and parent-line potatoes (fieldgrown at IACR, Rothamstead, England) re-grown under closely controlled conditions in tunnels or glasshouses side-by-side indicated that the contents of some or all of the constituents of major nutritional importance in GM-potatoes were significantly different from those of the parent lines. Moreover, the composition of the two GM lines were also significantly different. Thus, one of the GM lines had significantly less protein than the parent line or the second GM potato line. The contents of starch, glucose and antinutrients of the GM- and appropriate parent lines, such as the tuber lectin, trypsin inhibitors and chymotrypsin inhibitors were also significantly different. These results in conjunction with the findings by SCRI scientists thats foliar glycoalkaloid content in various lines of GM-potatoes was decreased clearly "indicate possible gene silencing, suppression and/or somaclonal variation" as a result of the GNA gene insertion. Thus, the GNA-GM-potato lines investigated by us were not "substantially equivalent" to the appropriate parent tubers or to each other.
  2. Four major feeding trials, three for 10 days and one for 110 days, with young rats were carried out. The results showed that in comparison with diets based on parent line potatoes with or without being spiked with GNA, the general metabolism, organ development and immune responsiveness of rats fed iso-proteinic and iso-energetic diets containing GM potatoes was significantly different, demonstrating that the design of our nutritional experiments was sufficiently sensitive to show up the very real and significant compositional differences between these different lines of potatoes. Thus, in the three 10 day trials with GNA-GM-potatoes significant changes in the weights of some of the rat vital organs were observed which were to a large extent not due to the expression of the GNA gene in the GM potatoes and also somewhat independent of the protein concentration in the diet. Multivariate statistical analyses indicated that although the treatment effects were small, the number of significant differences in organ weights was more than would be expected from Type I error rate, suggesting that, similar to the lack of compositional equivalence, the metabolic consequences of feeding GM-and parent potatoes were also substantially different even though "potato GNA" in GNA-GM-potato diets appeared to be functionally similar to "snowdrop GNA" in GNA-spiked diets. The presence of GNA-GM-potatoes in the diet for 10 days significantly reduced the rats' lymphocyte responses to mitogenic stimuli compared to parents and these differences could not have occurred by chance and were not due to the expression of GNA.

Accordingly, the existing data support our suggestion that the consumption by rats of transgenic potatoes expressing GNA has significant effects on organ development, body metabolism and immune function that is fully in line with the significant compositional differences between transgenic and corresponding parent lines of potatoes. The results also suggest that a major part of these differences was not caused by the expression of the GNA gene in the transgenic potato lines but that these could have been due to the presence of one or more of the other gene(s) in the vector used in the gene transfer or to the possibility of disturbances in the functioning of potatoes' own genes caused by the random incorporation of the vector in the potato genome (positioning effect).

A follow-up gut histology study (1), the results of which will be separately discussed in Dr Stanley. W.B. Ewen's submission, indicated that the the difference in the rats' responses to diets containing GM or untransformed potatoes could have primarily been the result of an unexpected and for the time being unknown mitogenic, growth-stimulating effect of the GM potatoes on most compartments of the rat gastrointestinal tract (GIT), including the pancreas. This remarkable effect could not be ascribed to the presence of GNA in the GM potatoes because supplemented GNA in over a hundredfold excess in control diets was shown previously and in the present study to have no such stimulatory effect. Although detailed histology studies similar to ours are scarce, there is some evidence, some of which is published, to support our suggestion that such a mitogenic effect on the mammalian gut may also occur with other GM foodstuffs. Thus, in the original FLAVR SAVR tomato study done under an FDA (Food and Drug Administration) contract, there were indications that daily gavaging rats with GM tomato homogenates induced mild to medium gastritis symptoms in female rats (4). This study was subsequently not followed up because it was claimed by the FDA that the lesions were not treatment-related and only temporary. This claim, however, rather strange because the rats were only sampled once, at the end of the experiment, for gut histology. Interestingly, in a recent histology study both isolated Bacillus thuringiensis toxin (Bt-toxin) and also a Bt-toxin-expressing potato sample incorporated into the diet of laboratory rodents caused mitogenic, growth-stimulating effects in stomach and ileal tissues (5) which were similar to those found by us in our GM potato study (1). Thus, the fact that three separate studies carried ou in three different laboratories with three different GM crops expressing different gene products but using the same genetic engineering method raise the possibility that such a gut mitogenic effect may possibly be a general consequence of exposing the GIT of mammals to GM food. Although it is not clear at present whether there are any pathological consequences of this gut stimulating effect of GM foodstuffs, it should at least compel the regulatory authorities to demand to carry out follow up studies as part of a routine safety testing of present or novel GM foodstuffs.

In conclusion: our extensive nutritional, developmental and immune studies with GM potatoes expressing the GNA gene have shown that genetic engineering has not only substantially altered their composition but that it has also affected their nutritional value and wholesomeness. Although our study was abruptly terminated and it remains to be established whether its potential implications for human health could be substantiated, the often-heard view that there is no evidence which indicates the possibility of potential harmful effects of GM food, can no longer be maintained. There is an urgent need for an at least five year but preferably a ten-year moratorium for the inclusion of GM foodstuffs in the human/animal food/feedchain and also the start of a corresponding and intensive research programme to investigate the potential health hazards and the associated risks of GM food for both human and animal consumers. This will have to be done as per the motto of the Edinburgh OECD Conference: openly, transparently and inclusively with independent verification because without this the GM technology that promised so much for the 21st Century might not be accepted by the public and will disappear.


  1. Ewen SWB and Pusztai A, Lancet, 354, 1353-1354, 1999
  2. Pusztai A et al, Digestion, 46 (suppl 2), 308-316, 1990
  3. Pusztai A et al, J Appl Bacteriol, 75, 360-368, 1993
  4. IIT Research Institute, (Chicago, Ill 60616 USA) Final Report, 1991
  5. Fares NH and El-Sayed AK, Nat Toxins, 6, 219-233, 1998