Truth: The few studies that have been conducted on humans show problems

Myth at a glance

GM proponents claim that GM foods are extensively tested and have been found safe for people to eat. But this is false. GM foods are not properly tested for safety for human consumption before they are released for sale.

The few published studies that have directly tested the safety of GM foods for human consumption found potential problemsbut were not followed up.

All GM crops should be tested in long-term studies on human volunteers prior to commercialization.

GM foods should be labelled as such and post-commercialization monitoring of populations consuming these foods should be carried out.

GM proponents claim that GM foods are extensively tested and have been found safe for people to eat. But this is false. GM foods are not properly tested for safety for human consumption before they are released for sale.1,2 The only published studies that have directly tested the safety of GM foods for human consumption found potential problemsbut were not followed up. Findings include the following:

  • In a study on human volunteers fed a single GM soybean meal, intact GM DNA was found to survive processing and was detected in the digestive tract. There was also evidence for the presence of intact GM gene units in the digesta (food undergoing digestion) of some of the subjects and of horizontal gene transfer of the glyphosate herbicide-tolerance GM gene to gut bacteria.3,4 Horizontal gene transfer is a process by which DNA is transferred from one organism to another through mechanisms other than reproduction.
  • In a study in humans testing immune response to wild-type non-GM soybeans and GM soybeans, skin test results from 49 patients showed that 13 had immune responses to wild soybeans and eight to GM soybeans. One of the experimental subjects showed an immune response to GM soy but not to non-GM soy. GM soy was found to contain a protein that was different from the protein in non-GM soy.5 Most allergies are to proteins. This study does not show that GM soy is more allergenic than non-GM soy, but it does show that GM foods could cause new allergies that are not predictable from analysis of a person’s immune response to non-GM versions of the same food.
  • A GM soy variety modified with a gene from Brazil nuts was found to react with antibodies present in blood serum taken from people known to be allergic to Brazil nuts. Based on current immunological knowledge, this observation indicates that this soy variety would produce an allergic reaction in people allergic to Brazil nuts.6
  • A study conducted in Canada detected significant levels of the insecticidal protein, Cry1Ab, circulating in the blood of pregnant and non-pregnant women and in the blood supply to foetuses.7 This insecticidal protein is present in GM Bt crops as well as in insecticidal sprays used in chemically-based and organic farming. How the Bt toxin protein got into the blood (whether through food or another exposure route) is unclear. The validity of the detection method used was disputed by Monsanto,8 but Monsanto’s objections have been answered by the authors of the original study.9 The study raises questions as to why GM Bt crops are being commercialized widely without investigating the fate and potential effects of Bt toxin in humans.

Conclusion

The above studies show potential problems from GM food consumption and should be followed up with further research. All GM crops should be tested in long-term studies on human volunteers prior to commercialization. In the absence of such testing, GM foods and crops should not be commercialized.

GM foods should be labelled as such in all countries and post-commercialization monitoring of populations consuming these foods should be carried out.

References

  1. Freese W, Schubert D. Safety testing and regulation of genetically engineered foods. Biotechnol Genet Eng Rev. 2004:299-324.
  2. Pusztai A, Bardocz S. GMO in animal nutrition: Potential benefits and risks. In: Mosenthin R, Zentek J, Zebrowska T, eds. Biology of Nutrition in Growing Animals.Vol 4. Elsevier Limited; 2006:513–540. Available at: http://www.sciencedirect.com/science/article/pii/S1877182309701043.
  3. Netherwood T, Martin-Orue SM, O’Donnell AG, et al. Assessing the survival of transgenic plant DNA in the human gastrointestinal tract. Nat Biotechnol. 2004;22:204–209. doi:10.1038/nbt934.
  4. Heritage J. The fate of transgenes in the human gut. Nat Biotechnol. 2004;22:170-2. doi:10.1038/nbt0204-170.
  5. Yum HY, Lee SY, Lee KE, Sohn MH, Kim KE. Genetically modified and wild soybeans: an immunologic comparison. Allergy Asthma Proc. 2005;26:210-6.
  6. Nordlee JA, Taylor SL, Townsend JA, Thomas LA, Bush RK. Identification of a Brazil-nut allergen in transgenic soybeans. N Engl J Med. 1996;334:688-92. doi:10.1056/NEJM199603143341103.
  7. Aris A, Leblanc S. Maternal and fetal exposure to pesticides associated to genetically modified foods in Eastern Townships of Quebec, Canada. Reprod Toxicol. 2011;31.
  8. Goldstein DA, Dubelman S, Grothaus D, G. Hammond BG. Comment: Aris and Leblanc “Maternal and fetal exposure to pesticides associated to genetically modified foods in Eastern Townships of Quebec, Canada.” Reprod Toxicol. 2012;33:120-121.
  9. Aris A. Response to comments from Monsanto scientists on our study showing detection of glyphosate and Cry1Ab in blood of women with and without pregnancy. Reprod Toxicol. 2012;33:122-123.