Genetically modified food and health – a cause for concern?

Foods containing genetically modified (GM) ingredients are on sale in Irish shops. In a survey of soya based foods undertaken by the Food Safety Authority of Ireland in 2002, over a half of the products tested contained genetically modified ingredients. Such products included baby foods and soya desserts. This soya bean contains a foreign gene from a common soil bacterium linked to cauliflower mosaic virus and petunia flower control elements. Foods containing GM ingredients may not be immediately apparent to the consumer, because if the GM ingredients constitute less than 1% of the product, there is no requirement for such labelling. It is of particular concern that five samples tested which contained GM ingredients were labelled as being free of such ingredients.

The availability of these products is a cause of serious concern, as there are good scientific grounds for the opinion that genetic engineering of plants designed to be eaten, may be harmful to health. GM is the process whereby genes that are associated with specific qualities are transferred to unrelated species by methods not seen in nature.

Genes are segments of DNA that specify the structure of proteins. The concept of GM emerged at a time when it was still believed that genes were simple carriers of single traits. However, modern research has established that no gene works in isolation and that the effect of a gene is dependent on its interaction with other genes and on its surroundings. Nevertheless, the insertion of the foreign genetic material is a random process, and occurs in the absence of normal promoter sequences and associated regulatory elements, which regulate the quantity, timing, and duration that each gene is expressed and subsequent protein interactions. The foreign genes are generally introduced into plant tissue or into tissue cultures in the laboratory by either being coated on tiny pellets of gold or tungsten and fired with a special gun, or else brought in via a microorganism. Indeed, it can be argued that gene transfer via current GM techniques resembles the process of viral infection far more closely than it resembles traditional breeding 1. However, the gene insertion process is very inefficient and requires that an antibiotic resistance marker gene be coupled to the desired foreign gene. This allows plants cells that have taken up the foreign gene to be selected by growth in the presence of the appropriate antibiotic. Once selected, GM transformed cells are stimulated to develop into fully mature plants. There are potentially serious health concerns arising from the use of the GM process. Overall the GM transformation process (foreign gene insertion plus tissue culture propagation of plant material) is known to be highly mutagenic and can cause hundreds or even thousands of disruptions to the ordinary command code sequence in the DNA and may disturb the functioning of the cell in unpredictable and potentially hazardous ways 2. These new genes will of course cause the creation of new proteins, which will generally be alien to the plant, and may, in the worst case, be toxic, allergenic or otherwise detrimental to heath. The characteristics of a protein with known allergenicity that would distinguish it from a protein unlikely to be allergenic are not known 4 and further difficulties in the elucidation of allergenicity, including the availability of allergen-specific antisera have also been outlined 5.

Approximately 40% of all GM foods on sale contain DNA from a soil bacterium, which produces an insecticide (Bt toxin), causing the plant to produce this chemical. As a result, such plants are classified as insecticides in the US 3. Although animal testing has given rise for serious concern, only a single peer-reviewed publication of clinical studies on the human health effects of GM food has been conducted 6. This study highlighted the possibility that GM material can potentially pass from the food to bacteria in the gut. These results raise concerns that antibiotic resistance marker genes present in the GM food could pass to potential pathogenic bacteria making them refractory to challenge with certain classes of antibiotics 7.

In the EU, extensive safety testing of GM foods is not required if the new plant is deemed to be ‘substantially equivalent’ to the parental plant. This term has no clear definition and no scientific meaning. The concept itself does not make sense, for if a GM plant is the same as its original counterpart, there would be no need to develop it in the first place. The lack of safety testing is disturbing. The regulation of GM food is currently based on a series of ‘extremely insufficient’ guidelines 8. In the US, there are no compulsory requirements for a biotechnology company to submit their GM food products to the Food and Drug Administration (FDA) for assessment. Little research has been conducted on unintended compositional changes from genetic engineering 9. More research is urgently needed. Issues of chronic toxicity, carcinogenesis and teratogenesis of genetically engineered foods need are seriously under-investigated 3. The results of research to date with animals are disturbing. Immune system damage and proliferation of the gastric mucosa have been found in rats fed GM potato 10, reductions in cellular metabolism and changes in the liver and pancreas in rats fed GM soya 11, allergic reactions and subsequent lung damage in mice fed GM peas 12 and a preliminary report indicating low-birth weight and fatalities in rats fed GM soya 13. A Monsanto-sponsored study involving rats being fed GM maize showed highly significant alterations in blood cell numbers (higher basophil/lymphocyte/white cell counts; lower reticulocyte counts) increased blood sugar and decreased kidney weight. The possibility has been raised 14 that an outbreak of respiratory and gastro-intestinal illnesses in the Philippines may have been caused by contact with GM maize. The myalgia illness and mortalities associated with the consumption of L-tryptophan produced from GM bacteria are well documented 15 as well as the fears generated when Starlink GM maize intended for animals was found in the human food chain, with consequent reports of allergic reactions in consumers. Children will have the longest exposure to GM food, and their vulnerability has been highlighted 16.

Acknowledging concerns that much research into possible adverse health effects from GM foods is needed, the State Government in Western Australia announced in 2005 that it would fund laboratory testing on rats to determine the safety of GM food crops. Researchers in the National Institute of Health, (Bethseda, USA) have stated that “there is growing concern among the general public and the scientific community, regarding the potential toxicity of genetically engineered organisms” 4.

To accurately assess any adverse health impacts, it is necessary to have baseline health data collected prior to the introduction of the food under surveillance 17. However, little or no such information is available globally, leading to the situation whereby it is virtually impossible to link adverse health impacts with the ingestion of GM food. In addition, the introduction of herbicide tolerant plants in the US has been associated with increased use of pesticides 18, and Ireland does not have a register of pesticide-associated illness. The accuracy of testing of existing foodstuffs for the presence of GM products has also been questioned. Errors may enter the standard monitoring and the verification procedures, resulting in the situation that it is not possible to determine the extent of the uncertainty that a consignment of food or seed is free of GM products 19. Other limits of post market assessment in relation to the detection of possible adverse health effects of GM food, have been outlined 5 and include such issues as treatment being usually symptomatic and undocumented, and in addition, the potential allergen being seldom identified.

The close links between the GMO industry and the European Food Safety Authority (EFSA) have been outlined, and this authority appears to take a less precautionary approach than many of its national members 20. Recommendations have been made that the EFSA publish the criteria it would use to assess whether GM food had side effects, as at present it is unclear 20.

It is not acceptable that statutory agencies use guidelines that do not reflect current health concerns. In addition, health surveillance systems at present in Ireland are not adequate to detect adverse health effects should they arise. Aside from the possible adverse health effects of consuming GM food, containment of GM seed is not possible. Seeds will spread by wind, and by people and animals.

If planting of genetically engineered crops is allowed in Ireland, we will leave an irreversible legacy to future generations and will be guilty of a deliberate betrayal of their interests. Doctors have an ethical and moral duty to highlight concerns in relation to these issues, and in the interest of health of present and future generations, permission to grow or consume genetically engineered foods in Ireland should be denied.

I would like to thank Dr. Michael Antoniou for reading a previous version of this article.

E Cullen*

Thomastown, Kilcullen, Co. Kildare
*Irish Doctor’s Environmental Assoc.


  1. Brown P. The Promise of plant biotechnology, the threat of genetically modified organisms Professor College of Agriculture & Environmental Science University of California Davis, Accessed 29-12-06
  2. Latham JR, Wilson AK and Steinbrecher RA, The Mutational Consequences of Plant Transformation. J Biomed Biotechnol. 2006(2):25376
  3. Ewen S Proceedings of the Green Ireland Conference • Kilkenny Castle, 16-18 June 2006
  4. Metcalf D. What Are the Issues in Addressing the Allergenic Potential of Genetically Modified Foods? ‘Environ Health Perspect.2003 Vol 111 1110-3
  5. Bernstein JA, Bernstein L, Bucchini L, et al.; Clinical and Laboratory Investigation of Allergy to Genetically Modified Foods Environ Health Perspect. 2003 Vol 111:1114-1121.
  6. Netherwood T, Martín-Orúe SM, O’Donnell AG, et al.;. Assessing the survival of transgenic plant DNA in the human gastrointestinal tract. Nat Biotechnol 2004 22, 204 – 209,
  7. Heritage J. The fate of transgenes in the human gut. Nat Biotechnol 2004 22:170 – 172,
  8. Pyrme R and Lembcke R In vivo studies on possible health consequences of genetically modified food and feed – with particular regard to ingredients of genetically modified plant materials Nutrition and Health 2003 Vol I pp 1-817
  9. Pelletier DL Science, law, and politics in FDA’s genetically engineered foods policy: scientific concerns and uncertainties Nutr Rev 2005 Jun;63( Pt1):210-23
  10. Ewen SW, Pusztai A, Effect of diets containing genetically modified potatoes expressing Galanthus nivalis lectin on rat small intestine Lancet. 1999 Oct 16;354(9187):1353-4.
  11. Malatesta M, Caporaloni C, Gavaudan S, et al. Ultrastructural morphometrical and immunocytochemical analyses of hepatocyte nuclei from mice fed on genetically modified soybean. Cell Structure and Function 2002 27, 173-180.
  12. Prescott VE, Campbell PM, Moore A, et al Transgenic Expression of Bean -Amylase Inhibitor in Peas Results in Altered Structure and Immunogenicity Agric. Food Chem., 2005 53 (23), 9023 -9030
  13. Ermakova I.V. Influence of genetically modified soya on the birth weight and survival of rat pups: Preliminary study Presented 10 Oct 2005 National Association for Genetic Security On file
  14. Traavik T Filipino islanders blame GM crop for mystery sickness The Guardian Wednesday March 3, 2004
  15. Mayeno AN and Gleich GJ. Eosinophilia-myalgia syndrome and tryptophan production: a cautionary tale Trends Biotechnol. 1994 12: 346-352.
  16. Perr HA Children and genetically engineered food: potentials and problems J Pediatr Gastroenterol Nutr 2002 Oct;35(4): 475-86
  17. Germolec DR, Kimber I, Goldman L, et al, Key Issues for the Assessment of the Allergenic Potential of Genetically Modified Foods: Breakout Group Reports Environ Health Perspect 2003 111:1131-1139
  18. Benbrook CM Impacts of Genetically Engineered Crops on Pesticide Use in the United States: The First Eight Years BioTech InfoNet 2003 Technical Paper No 6
  19. Heinemann JA, Sparrow AD, Traavik T, Is confidence in the monitoring of GE foods justified? Trends Biotechnol 2004 ;22(7):331-6
  20. FOE 2004 Friends of the Earth Throwing Caution to the Wind Accessed 4 January 2007