GM Free Cymru

Health Risks of Genetically Modified Foods

Health Risks of Genetically Modified Foods
Critical Reviews in Food Science and Nutrition, 49:164–175 (2009)2

As genetically modified (GM) foods are starting to intrude in our diet concerns have been expressed regarding GM food safety. These concerns as well as the limitations of the procedures followed in the evaluation of their safety are presented. Animal toxicity studies with certain GM foods have shown that they may toxically affect several organs and systems. The review of these studies should not be conducted separately for each GM food, but according to the effects exerted on certain organs it may help us create a better picture of the possible health effects on human beings. The results of most studies with GM foods indicate that they may cause some common toxic effects such as hepatic, pancreatic, renal, or reproductive effects and may alter the hematological, biochemical, and immunologic parameters. However, many years of research with animals and clinical trials are required for this assessment. The use of recombinant GH or its expression in animals should be re-examined since it has been shown that it increases IGF-1 which may promote cancer.


The lasting sceptical and/or ambivalent attitude of Europeans towards agro-food biotechnology and the continued controversies about the commercialization of transgenic agro-food products are illustrative of an ongoing legitimacy crisis. One could even interpret the stigma on agro-food biotechnology and its products as testifying to a “robust” societal disapproval: it signals a lack of trust in scientific institutions and expert systems, and voices a social response against the reduction of the complexity of the GMO issue to a solely scientific risk-based problem. Hence, amove from a merely scientific evaluation towards a socially more robust one—that addresses precaution and socioethical issues in a more “sensible”way, whilst making “sense” of the different stances taken in the GMO debate—is still sought after. It will be interesting to see whether new controversies show (triggered, for example, by GMO contaminations or traces of unapproved transgenic events in nontransgenic produces), how these will be communicated and developed in the societal climate, and how they will be interpreted and tackled by, and/or lead to new adjustments in the now running legal system (Devos et al., 2007). The comparison of values relevant to GE crops and foods among EU, Japan, Canada, and the USA is given in Table 2.

From the review of the toxicity studies concerning GMfoods one might see that although toxicity can be assessed, the duration of exposure is too short in order to fully evaluate any potential disruptions in biochemical parameters and to evidence possible signs of pathology within the limited subchronic exposure of animals. Moreover, a larger number of animals should be used in the toxicity tests. The toxicity tests should comply with the guidelines for toxicity testing of drugs. It should be emphasized that since these GM foods are going to be consumed by every human being they should be tested even more thoroughly than drugs and more experiments are required in order to study the possible toxicity and make any conclusions. Tests to determine how a GM food affects mutagenesis and carcinogenesis should be conducted as well. Finally, postmarketing surveillance should be part of the overall safety strategy for allergies, especially of high-risk groups such as infants and individuals in “atopic” families. Evaluation of protein allergenicity in man should also include studies in individuals not only with a history of allergy but with immunodeficiency as well. The use of recombinant GH in animals, such as cows or the expression of GH in animals such as salmon should be re-examined since it may promote cancer. The results of most of the rather few studies conducted with GM foods indicate that they may cause hepatic, pancreatic, renal, and reproductive effects and may alter hematological, biochemical, and immunologic parameters the significance of which remains unknown. The above results indicate that many GM food have some common toxic effects. Therefore, further studies should be conducted in order to elucidate the mechanism dominating this action. Small amounts of ingested DNA may not be broken down under digestive processes and there is a possibility that this DNA may either enter the bloodstream or be excreted, especially in individuals with abnormal digestion as a result of chronic gastrointestinal disease or with immunodeficiency. Although intensive scientific effort is currently in progress to thoroughly understand and forecast possible consequences on humans, animals, and the environment, it is anticipated that many years of careful, independent research with animals and clinical trials will be needed in order to accomplish this assessment.


Note that this is a review paper, not a primary research paper. Nevertheless, we are including it here as one of our "Crucial Papers" because it deserves to be widely read. This is a carefully researched and well-referenced paper which looks at all of the known health risks associated with GM foods. As with most academic publications, the language is cautious, but the authors note a common theme arising from many independent studies of health effects -- the apparently toxic effects of GMOs on internal organs and on the reproductive system. They pick up on the shortcomings of the normal "safety testing" protocols, including the short exposure times experienced by tested animals -- often far too short for GM-related effects to become apparent. They call for testing protocols which are more stringent than drug testing protocols -- on the basis that GM foods are likely (if approved) to be consumed by everybody -- and not just by groups in the population who may be deemed to require "healing." Unusually in a paper of this type, the authors also consider ethical issues, arguing that there is broad societal disapproval of GM crops and foods, based on a lack of trust in scientific institutions and expert systems. The authors argue that in a democracy socio-economic factors should be given much more weight in the regulatory process, since the public will not accept the reduction of the complexity of the GMO issue to a solely scientific risk-based problem.