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GM food can cause cancer

The human health risks associated with genetically modified food have deliberately been underplayed. The 'scientific loudspeakers' of the GM industry have been so orchestrated that the moment you mention the health impact of the genetically altered foods, they pounce upon you like vultures. The reason is obvious: the financial stakes involved are so high that the industry is desperately trying to keep the food scare out of the ongoing debate.

The British Medical Association (BMA) efforts to stand up despite the industrial pressure is therefore laudable. The BMA has been relentlessly asking for more scientific studies to evaluate the long-term impacts on human health. For some strange reasons, in India and for that matter in other developing countries, the medical fraternity is woefully quiet on the health risks associated with GM foods. Perhaps the main reason being that the GM foods have still to be part of food menu in the developing world.

We present two reports, which warn against ignoring the health risks of GM foods.

1. GM expert warns of cancer risk from crops

Demand for executive to ban crop trials until effects of GM food on health are studied

By Rob Edwards, Environment editor

EATING genetically modified (GM) food could give you cancer. That is the stark warning today from one of Scotland's leading experts in tissue diseases.

Dr Stanley Ewen, a consultant histopathologist at Aberdeen Royal Infirmary, says that a cauliflower [mosaic] virus used in GM foods could increase the risk of stomach and colon cancers.

He is calling for the health of people who live near the farm-scale GM crop trials in Aberdeenshire, Ross-shire and Fife to be monitored. Their food and water will be contaminated by GM material, he said, which could hasten the growth of malignant tumours.

'I don't want to be scare-mongering, I want to be understated,' Ewen told the Sunday Herald. 'But I'm very concerned that people who rely on local produce might be endangering themselves.'

The government, backed by its scientific advisors, has always insisted the GM trials pose no risk to human health or the environment. Nevertheless, the trials have provoked widespread opposition, with dozens of protesters arrested for damaging GM crops.

Ewen's warning, which has been delivered to the Scottish Parliament's Health and Community Care Committee, is bound to be seized on by critics . The committee is just completing an investigation into the safety of GM food and is hoping to report its findings this week.

Ewen, who has 29 years' experience as a histopathologist, is currently leading a pilot project in Grampian to screen people for colon cancer. In 1999, along with Dr Arpad Pusztai, a former researcher at Aberdeen's Rowlett Institute, he published a study suggesting that GM potatoes harm rats.

In his submission to the health committee, Ewen expressed 'great concern' about the use of the cauliflower mosaic virus as a 'promoter' in GM foods. The virus is used like a tiny engine to drive implanted genes to express themselves.

But Ewen pointed out that the virus is infectious, and could act as a 'growth factor' in the stomach or colon, encouraging the growth of polyps. The faster and bigger polyps grow, the more likely they are to be malignant, he added.

There are also risks in feeding GM products like maize to cattle, he cautioned.

'It is possible cows' milk will contain GM derivatives that can be directly ingested by humans as milk or cheese. Even a lightly cooked, thick fillet steak could contain active GM material.'

GM material can be destroyed by cooking or boiling for 10 minutes, and it can be broken down by the acids and enzymes in the stomach. But Ewen is worried that genes in uncooked GM fruit and vegetables could survive common stomach infections.

'It is possible GM DNA could affect stomach and colonic lining by causing a growth factor effect with the unproven possibility of hastening cancer formation in those organs,' he stated.

Ewen stressed that he is not opposed to all GM technology, which he believes could have real benefits, particularly in medicine. But he is sufficiently alarmed by the current use of the technology to urge the health committee to call for a ban on GM crop trials while their safety is tested on animals.

Doctors from the British Medical Association have also suggested a GM ban to the committee because of the unknown effects on health. The committee's investigation was prompted by a petition of 6000 signatures gathered by protesters who maintained a vigil at a GM trial site at Munlochy in Ross-shire.

'What is most worrying about Dr Ewen's evidence is that while his concerns are disease-specific, the risks extend to a wide range of GM food crops,' said Jo Hunt, director of the lobby group Highlands and Islands GM Concern.

'The effects are caused not by just one 'bad' DNA fragment, but are a result of the reaction of plant cells to genetic engineering itself. All the major GM food plants currently produced could have the same effect when eaten.'

Hunt argued that long-term research was needed to establish whether GM food was safe. 'But instead of looking at the impact of GM food on people's health, the Scottish Executive has spent over 5 million on farm-scale trials to see how growing GM crops on Scottish farms will affect butterflies and weeds. The Executive has already released GM at 11 sites and is considering allowing GM to be released anywhere in the country from 2004, before it knows whether GM food is safe to eat.'

The Executive also came under fire from the Scottish National Party's shadow environment minister, Bruce Crawford, who demanded a freeze on GM crops trials. 'We cannot allow GM material to enter the food chain until there are absolute guarantees that there are no risks,' he said.

He pointed out that, in a recent letter, the environment minister, Ross Finnie, had admitted to him that plants around GM crops could become contaminated. Finnie added, however, that the government's advice was 'unanimous in its conclusion that GM crops that have approval do not pose a safety threat.'

2. Submission of evidence to the Clerk to the Health and Community Care Committee of The Scottish Parliament

Dr Arpad Pusztai, FRSE

Health Impact of GM Crops

1. For reasons based on the precautionary principle as reinforced by the results of our research on GM potatoes carried out between 1995 and 1998 and funded by the then SOAEFD and other evidence as detailed below under point 2 of the original questionnaire the Scottish Executive should prevent the continuation and the starting up of further new GM crop trials so as not to jeopardize the health of the peoples of Scotland and also to prevent the Scottish countryside from irreversible genetic contamination that may threaten the health of future generations of the land.

2. Regulatory framework

The risk assessment procedure for GM crops currently in place is not sufficiently robust to ensure public health and safety because the regulatory process is fundamentally flawed. GM-foodstuffs are presently accepted on the basis of their "substantial equivalence" to their non-GM counterparts. This concept is not only unscientific but also potentially dangerous because the present analytical methods used for establishing equivalence do not allow for the discovery of new antinutrients, toxins and allergens formed as the unintended consequence of the genetic transformation of the crops. This fault is compounded by the practice of the regulatory authorities' almost exclusive reliance on unpublished results of "in house" work of the biotech companies contained in their submission. Even if these are scientifically valid, they fall down on the public's (and other scientists') demand of transparency because it is not required by the regulatory authorities that the results of biological risk assessment or nutritional/physiological studies carried out with GM-crops should be made available for scrutiny to other scientists and interested persons and published in peer-reviewed journals. Moreover, if the regulators wish to confirm or reject any of the results in the submissions, their hands are tied because they cannot commission new independent work. As the forte of most of their members is scientific administration, the Committees should not only be strengthened by the presence of consumer and environmental pressure groups but also by the appointment of active scientists of different disciplines.

The lack of proper science basis of crop genetic modification

The present method of gene transfer which enables scientists to transform any plant using virus and antibiotic resistance genes and which is now the dominant technique for the creation of GM crops is based on the fundamentally flawed principle of genetic determinism, requiring that one gene expresses only one protein but without influencing the expression of other genes or without other genes and gene networks influencing the expression of the gene newly transferred into the crop plant genome. However, as a result of the human genome project we now have incontestable evidence that this is not true and therefore all present GM crops are the products of the same imprecise and unpredictable technology that may harm both human health and the environment. Additionally, the use of naked viral DNA promoters which are known to be hotspots of recombination with host DNA and may induce horizontal gene transfer, the inclusion of antibiotic resistance genes in the gene-transfer construct and the unpredictability of both the site of insertion and its consequences for the plant genome makes this method unacceptable. In addition, present day GM-crops designed for increased pest resistance, such as those expressing Bacillus thuringiensis lectin endotoxins (Bt toxin crops), are not sufficiently selective and specific for their major pests and, by inflicting damage to beneficial insects, they destroy the natural balance between pests and useful organisms. Neither have these crops be shown to be harmless for human/animal consumers. Indeed, there is good peer-reviewed published evidence to show that Bt toxins are both immunogens and immunoadjuvants for mammals and as such they have profound influence on the functioning of both the humoral and mucosal immune systems1. Moreover, it has also been shown that Bt toxins bind to the mammalian small intestine and have major effects on its proper functioning(2).

Comparison of the potential health risks of GM vs. conventional foods

The often-heard statement that GM crops are just another cultivar is simply untrue. No viral, bacterial or mammalian DNA found in present day GM crops resulting from the process of genetic transformation could have been introduced into the plant genome by natural means or traditional cross-breeding. GM-food therefore contains foreign genes and their products that may not have ever been eaten before and whose effects on health and metabolism of mammals are unknown, unpredictable and untested. Although most nutritional journals are full of papers of animal feeding studies in which the nutritional value and potential harmful effects of plant based conventional feedstuffs are evaluated, only a handful of such studies with GM-crops have been published in peer-reviewed science journals(3). Moreover, except our two published studies(4,5) most of these published articles have resulted from the work of biotech imdustry scientists. With the exception of a present FSA (Food Standard Agency) sponsored but unpublished study with human volunteers with externally fitted intestinal pouches who were given a single dose of GM soya-based food, the possible health effects on the human digestive tract and its bacterial population have never been tested. This is the more serious because this study showed evidence that bacteria in the pouch contained pieces of DNA used in the genetic conversion, clearly demonstrating that horizontal gene transfer is not only a theoretical possibility but also a reality. It is also expected that with the likely prospect of the inclusion of more GM-crops into the human diet in future, such as unprocessed/uncooked greens, vegetables, fruits, etc, the potentially harmful effects of foreign DNA and gene products on human/animal health will be substantially increased, particularly because of "tradition" these crops are accepted as a matter of course and without proper testing.

The results of our GM potato studies and their possible consequences for human health

In 1995 we started a publicly-funded (by the then Scottish Office Agriculture, Environment and Fisheries Department, SOAEFD) major scientific investigation into the possible environmental and health hazards of GM-potatoes that had been transformed by British scientists using a gene taken from snowdrop bulbs. This is still to date the only truly independent investigation of the potential health effects of a GM crop. The gene of this sugar-recognizing protein (GNA) has been known to give natural protection against insect pests. We have also shown in extensive and appropriate nutritional studies carried out by our research group at the Rowett Research Institute in Aberdeen before the genetic modification of our potatoes with the GNA gene that animals ingesting this protein as part of their diet even at an 800-fold excess of that present in GM-potatoes, suffered no significant harmful consequences. We have, therefore, expected it to be safe for animal and, later after appropriate testing, possibly for human consumers. Unfortunately, our expectations were dashed as our studies revealed that the two lines of field-grown GM-potatoes which originated from the same transformation and were both resistant to aphid pests were not substantially equivalent in composition to parent line potatoes, nor to each other. Even more importantly, we showed from the results of four rat feeding studies of different designs and durations (10 to 110 days) that diets containing GM potatoes in comparison with iso-proteinic and iso-energetic non-GM parent potato diets had in some instances interfered with the growth of young rapidly growing rats, the normal development of some of their vital organs, induced changes gut structure and function and reduced their immune responsiveness to injurious antigens. In contrast, the animals fed on diets containing the parent, non-GM-potatoes or these potatoes supplemented with the gene product had no such effects. Some of these results has been published(4-7) and are also given on my own website:

Our findings have been attacked by many but never materially disproved by repeating our work, coming to different conclusions and publishing these. Thus, these people have only voiced their personal opinions which have no scientific standing and should be ignored. Our work has in fact clearly demonstrated that, in addition to possible toxicological studies, the safety of GM-foodstuffs must be established in short- and long-term feeding, metabolic and immune-response studies with young animals as these should be the most appropriate to respond to and show up any nutritional and metabolic stresses affecting the normal development of young animals into healthy adults a view that is shared by other scientists. Multivariate statistical analysis of our results carried out independently by SASS (Scottish Agricultural Statistics Service) has suggested that the major potentially harmful effects of our GM-potatoes were only in part caused by the presence of the GNA transgene but that the method of genetic transformation and/or the disturbances in the potato genome also made major contributions to the changes observed.

The method of genetic engineering we used for the transformation of the potatoes was almost identical to most if not all the GM-crops released to date and it is now clear that none of these have been subjected to rigorous nutritional, metabolic and immunological testing similar to ours. As our GM-potatoes have not been released because their possible hazards for human/animal consumers, our results suggest that all GM-foodstuffs produced by the same/similar genetic engineering methodology ought to be withdrawn from human food products and animal feeds until and unless appropriate, rigorous safety tests could be carried out on them to show that they had no harmful effects. Moreover, no further field trials of GM crops or releases of GM foods must be allowed until they are shown to present no or minimal risks for consumers and/or the environment by commonly agreed, independently carried out and transparently reported nutritional, metabolic, toxicological and immune safety tests. This should equally apply to so-called second generation GM-crops with apparent nutritional advantages because presently the methodology used for their development is similar to that of other present GM-crops. In addition, to the relatively short-term safety assessment, the possible long-term adverse effects of GM-crops on animal reproduction must be established, with particular attention to the use of parasitoid DNA components, such as viral and bacterial promoters, plasmids, antibiotic resistance genes, etc. The long-term effects of these on horizontal gene transfer, DNA recombination and incorporation into the genome of bacteria, viruses, plants and animals must also be addressed by fundamental and independent academic studies. Indeed, we need to re-think the whole strategy of genetic engineering and because of its potential importance for and effect on mankind it should not be left to the decision of a few multinational companies. We have to find appropriate and transparent ways for independent and publicly-funded scientists together with the industry, religious, political leaders, NGO-s and other legitimate and interested stake-holders and members of the public to debate and finally agree as how to solve this problem for the common good while all the time keeping the precautionary principle as our guiding light to avoid any reckless adventures.

3. Even though I have my opinion on possible cross-contamination of conventional crops by GM crops, I am no expert and therefore make no comments on this point.

4. The answer is a most definite yes to the question whether the Scottish Executive ought to monitor the health of people living around the GM farm scale evaluation sites for reasons as detailed under point 2 of my submission. As some of the methods used in our rat studies and other non-invasive techniques such as blood sampling, immune responsiveness and gut/faecal bacterial DNA tests and possibly even histopathology of gut biopsy samples are even more conveniently applicable to humans than to small laboratory animals, no legitimate objections could be raised against such health monitoring. Quite the contrary, the results of monitoring could make a long-overdue scientific contribution to a rather sterile and non-factual but opinion-based debate on the possible health consequences for people of exposure to GM-crops and GM-food.


1. RI Vazquez Padron et al (1999) Intragastric and intraperitoneal administration of Cry1Ac protoxin from Bacillus thuringiensis induces systemic and mucosal antibody responses in mice. Life Sciences, 64, 1897-1912.

2. NH Fares and AK El-Sayed (1998) Fine structural changes in the ileum of mice fed on delta-endotoxin-treated potatoes and transgenic potatoes. Natural Toxins, 6, 219-233.

3. A Pusztai (2001) Genetically modified foods: are they a risk to human/animal health? (and in press).

4. A Pusztai et al. (1999) Expression of the insecticidal bean alpha-amylase inhibitor transgene has minimal detrimental effect on the nutritional value of peas fed to rats at 30% of the diet. The Journal of Nutrition, 129, 1597-1603.

5. SWB Ewen an A Pusztai (1999) Effects of diets containing genetically modified potatoes expressing Galanthus nivalis lectin on rat small intestine. The Lancet, 354, 1353-1354.

6. A Pusztai (2002) Can science give us the tools for recognizing possible health risks of GM food? Nutrition and Health (2002) 16, 73-84 7. A Pusztai (2002) GM food safety: Scientific and institutional issues. Science as Culture, 11, 70-92.

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