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Environ Int. 2014 Dec;73:423-33. doi: 10.1016/j.envint.2014.08.018. Epub 2014 Sep 20.

GM crops and the rat digestive tract: a critical review.

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Discipline of Anatomy and Pathology, School of Medical Sciences, University of Adelaide, SA 5005, Australia.
Health and the Environment, School of the Environment, Flinders University, Bedford Park, SA 5042, Australia.
Health and the Environment, School of the Environment, Flinders University, Bedford Park, SA 5042, Australia; Institute of Health and Environmental Research (IHER), P.O. Box 155, Kensington Park, SA 5068, Australia. Electronic address:


The aim of this review is to examine the relationship between genetically modified (GM) crops and health, based on histopathological investigations of the digestive tract in rats. We reviewed published long-term feeding studies of crops containing one or more of three specific traits: herbicide tolerance via the EPSPS gene and insect resistance via cry1Ab or cry3Bb1 genes. These genes are commonly found in commercialised GM crops. Our search found 21 studies for nine (19%) out of the 47 crops approved for human and/or animal consumption. We could find no studies on the other 38 (81%) approved crops. Fourteen out of the 21 studies (67%) were general health assessments of the GM crop on rat health. Most of these studies (76%) were performed after the crop had been approved for human and/or animal consumption, with half of these being published at least nine years after approval. Our review also discovered an inconsistency in methodology and a lack of defined criteria for outcomes that would be considered toxicologically or pathologically significant. In addition, there was a lack of transparency in the methods and results, which made comparisons between the studies difficult. The evidence reviewed here demonstrates an incomplete picture regarding the toxicity (and safety) of GM products consumed by humans and animals. Therefore, each GM product should be assessed on merit, with appropriate studies performed to indicate the level of safety associated with them. Detailed guidelines should be developed which will allow for the generation of comparable and reproducible studies. This will establish a foundation for evidence-based guidelines, to better determine if GM food is safe for human and animal consumption.


Gastrointestinal tract; Genetically modified crop; Histopathology; Long-term feeding studies; Rat feeding study

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