On the safety of GM crops and foods -- a review of the science
This is an extract from an excellent review published on the GM Watch web site:
http://www.gmwatch.eu/gm-crops-research-documenting-the-limitations-risks-and-alternatives
Are GM foods safe to eat? Contrary to industry claims, GM foods are not properly tested for human safety before they are released for sale3 4. In fact, the only published study directly testing the safety of a GM food on humans found potential problems5. To date, this study has not been followed up.
Typically the response to the safety question is that people have been eating GM foods in the United States and elsewhere for more than ten years without ill effects and that this proves that the products are safe. But GM foods are not labelled in the US and other nations where they are widely eaten and consumers are not monitored for health effects.
Because of this, any health effects from a GM food would have to meet unusual conditions before they would be noticed. The health effects would have to:
• occur immediately after eating a food that was known to be GM (in spite of its not being labeled). This kind of response is called acute toxicity. • cause symptoms that are completely different from common diseases. If GM foods caused a rise in common or slow-onset diseases like allergies or cancer, nobody would know what caused the rise. • be dramatic and obvious to the naked eye. Nobody examines a person’s body tissues with a microscope for harm after they eat a GM food. But just this type of examination is needed to give early warning of problems such as pre-cancerous changes. To detect important but more subtle effects on health, or effects that take time to appear (chronic effects), long-term controlled studies on larger populations are required.
Under current conditions, moderate or slow-onset health effects of GM foods could take decades to become known, just as it took decades for the damaging effects of trans-fats (another type of artificial food) to be recognized. ‘Slow poison’ effects from trans-fats have caused millions of premature deaths across the world6.
Another reason why any harmful effects of GM foods will be slow to surface and less obvious is because, even in the United States, which has the longest history of GM crop consumption, GM foods account for only a small part of the US diet (maize is less than 15% and soya bean products are less than 5%).
Nevertheless, there are signs that all is not well with the US food supply. A report by the US Centers for Disease Control shows that food- related illnesses increased 2- to 10-fold in the years between 1994 (just before GM food was commercialised) and 19997. Is there a link with GM food? No one knows, because studies on humans have not been done.
Animal studies on GM foods give cause for concern Although studies on humans have not been done, scientists are reporting a growing number of studies that examine the effects of GM foods on laboratory animals. These studies, summarized below, raise serious concerns regarding the safety of GM foods for humans as well as animals.
Small animal feeding studies • Rats fed GM tomatoes developed stomach ulcerations8 • Liver, pancreas and testes function was disturbed in mice fed GM soya9 10 11 • GM peas caused allergic reactions in mice12 • Rats fed GM oilseed rape developed enlarged livers, often a sign of toxicity13 • GM potatoes fed to rats caused excessive growth of the lining of the gut similar to a pre-cancerous condition14 15 • Rats fed insecticide-producing GM maize grew more slowly, suffered problems with liver and kidney function, and showed higher levels of certain fats in their blood16 • Rats fed GM insecticide-producing maize over three generations suffered damage to liver and kidneys and showed alterations in blood biochemistry17 • Old and young mice fed with GM insecticide-producing maize showed a marked disturbance in immune system cell populations and in biochemical activity18 • Mice fed GM insecticide-producing maize over four generations showed a buildup of abnormal structural changes in various organs (liver, spleen, pancreas), major changes in the pattern of gene function in the gut, reflecting disturbances in the chemistry of this organ system (e.g. in cholesterol production, protein production and breakdown), and, most significantly, reduced fertility19 • Mice fed GM soya over their entire lifetime (24 months) showed more acute signs of ageing in their liver20 • Rabbits fed GM soya showed enzyme function disturbances in kidney and heart21. Feeding studies with farm animals Farm animals have been fed GM feed for many years. Does this mean that GM feed is safe for livestock? Certainly it means that effects are not acute and do not show up immediately. However, longer-term studies, designed to assess slow-onset and more subtle health effects of GM feed, indicate that GM feed does have adverse effects, confirming the results described above for laboratory animals.
The following problems have been found:
• Sheep fed Bt insecticide-producing GM maize over three generations showed disturbances in the functioning of the digestive system of ewes and in the liver and pancreas of their lambs22. • GM DNA was found to survive processing and to be detectable in the digestive tract of sheep fed GM feed. This raises the possibility that antibiotic resistance and Bt insecticide genes can move into gut bacteria23, a process known as horizontal gene transfer. Horizontal gene transfer can lead to antibiotic resistant disease-causing bacteria (“superbugs”) and may lead to Bt insecticide being produced in the gut with potentially harmful consequences. For years, regulators and the biotech industry claimed that horizontal gene transfer would not occur with GM DNA, but this research challenges this claim • GM DNA in feed is taken up by the animal’s organs. Small amounts of GM DNA appear in the milk and meat that people eat24 25 26. The effects on the health of the animals and the people who eat them have not been researched. Do animal feeding studies highlight potential health problems for people?
Before food additives and new medicines can be tested on human subjects, they have to be tested on mice or rats. If harmful effects were to be found in these initial animal experiments, then the drug would likely be disqualified for human use. Only if animal studies reveal no harmful effects can the drug be further tested on human volunteers.
But GM crops that caused ill effects in experimental animals have been approved for commercialization in many countries. This suggests that less rigorous standards are being used to evaluate the safety of GM crops than for new medicines.
In fact, in at least one country – the United States – safety assessment of GMOs is voluntary and not required by law, although, to date, all GMOs have undergone voluntary review. In virtually all countries, safety assessment is not scientifically rigorous. For instance, the animal feeding studies that GM crop developers routinely conduct to demonstrate the safety of their products are too short in duration and use too few subjects to reliably detect important harmful effects.27
While industry conducts less than rigorous studies on its own GM products, 28 it has, in parallel, systematically and persistently interfered with the ability of independent scientists to conduct more rigorous and incisive independent research on GMOs. Comparative and basic agronomic studies on GMOs, assessments of safety and composition, and assessments of environmental impact have all been restricted and suppressed by the biotechnology industry.29 30
Patent rights linked with contracts are used to restrict access of independent researchers to commercialized GM seed. Permission to study patented GM crops is either withheld or made so difficult to obtain that research is effectively blocked. In cases where permission is finally given, biotech companies keep the right to block publication, resulting in much significant research never being published.31 32
The industry and its allies also use a range of public relations strategies to discredit and/or muzzle scientists who do publish research that is critical of GM crops.33
REFERENCES
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22. A three-year longitudinal study on the effects of a diet containing genetically modified Bt176 maize on the health status and performance of sheep. Trabalza-Marinucci M. et al. Livestock Science, 113: 178-190, 2008.
23. Fate of genetically modified maize DNA in the oral cavity and rumen of sheep. Duggan P.S. et al. Br J Nutr., 89: 159-166, 2003.
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26. Detection of Transgenic and Endogenous Plant DNA in Digesta and Tissues of Sheep and Pigs Fed Roundup Ready Canola Meal. Mazza R. et al. J Agric Food Chem. 54: 1699-1709, 2006.
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28. How Subchronic and Chronic Health Effects can be Neglected for GMOs, Pesticides or Chemicals. Séralini, G-E, et al. International Journal of Biological Sciences, 2009; 5(5):438-443.
29. Under wraps – Are the crop industry’s strong-arm tactics and close- fisted attitude to sharing seeds holding back independent research and undermining public acceptance of transgenic crops? Waltz, E., Nature Biotechnology, Vol. 27, No. 10, October 2009.
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33. Biotech proponents aggressively attack independent research papers: GM crops: Battlefield. Waltz, E., Nature 461, 2009, 27–32.