Researchers based out of Australia have found that pigs fed genetically engineered (GE) soy and GE corn are more likely to have severe stomach inflammation and higher uterine weight. Although the study, published in the peer-reviewed Journal of Organic Systems, has been criticized for its methodology, it underscores the need for more research on the long term impacts of GE consumption, especially considering the pig digestive system is physiologically similar to humans.


The study, “A long-term toxicology study on pigs fed  combined genetically modified (GM) soy and GM maize diet,” led by Judy Carman, PhD., associate professor in health and the environment at Flinders University, Australia, found that GE-fed pigs had much higher rates of stomach inflammation. Researchers fed 84 pigs GE soy and corn and 84 pigs non-GE feed for a period of 22.7 weeks, approximately the lifespan of a commercial pig from weaning to slaughter. While there were no differences in terms of other organ weight, feeding changes, mortality and blood biochemistry, 32 percent of GE-fed pigs contracted severe stomach inflammation in comparison to only 12 percent of pigs fed with non-GE feed. Interestingly, male pigs fed GE crops were much more likely to contract severe stomach inflammations: male GE-fed pigs were four times more likely to have stomach inflammation compared to non-GE fed pigs while GE-fed females were only 2.2 times more likely to have stomach inflammations than non-GE fed pigs. Researchers also found that GE-fed female pigs had on average a 25 percent heavier uterus than non-GM-fed females, which is a possible indicator of uterine diseases, including “endometrial hyperplasia or carcinoma, endometritis, endometriosis, adenomyosis, inflammation, a thickening of the myometrium, or the presence of polyps.”

The results have implications in the U.S., as GE soy now constitutes 94 percent of the soy planted, according to the U.S. Department of Agriculture (USDA). The proteins Cry3Bb1 and Cry1AB, which are inserted into crops to exhibit insecticidal properties, are called out by researchers as the likely culprit for the number of pigs with inflamed stomachs. The proteins effectively work by disintegrating gut tissues of grubs that attack corn. While many have argued that the proteins do not impact the intestinal tract of mammals, this study, as well as others, have shown otherwise.

Researchers conclude, “Given the widespread use of [GE] feed for livestock as well as humans this is a cause for concern…Humans have a similar gastrointestinal tract to pigs, and these [GE] crops are widely consumed by people, particularly in the USA, so it would be prudent to determine if the findings of this study are applicable to humans.”

The study’s methodology, however, has received harsh criticism from largely industry sources. Some have indicated the need to ensure that the two groups of pigs were fed completely equivalent diets except for their GE content, while others have pointed out that their statistical techniques to identify “severe” stomach inflammation did not account for the possibility of random chance occurrences. However, even critics of the study have conceded that the study was rigorously conducted, and that the results indicate the need for further research on the long-term health effects of GE crops.

In the meantime, using a precautionary approach to protect against the potential threats that GE crops may pose to human health is prudent.  The best way to avoid genetically engineered foods in the marketplace is to purchase foods that have the USDA certified organic seal. Under organic certification standards, genetically modified organisms and their byproducts are prohibited. For many other reasons, organic products are the right choice for consumers.