July 20, 2017

Toxicology Study on Pigs Fed GMO Foods Finds Problems

A study published in the Journal of Organic Systems, conducted by U.S. and Australian researchers on pigs fed genetically modified foods (GMOs), found problems with the animals given the altered foods. The animals fed GMO corn and soy had a higher rate of stomach inflammation and developed heavier uteri. This study was conducted because many feeding studies on the safety of GM crops use non-mammals that are not physiologically comparable to human beings, or animals that are fed the crop in a form that humans don’t eat. Other studies only measure body weight, carcass weight, breast meat or milk production yields and don’t consider health outcomes.

Scientists followed 168 pigs from weaning age to slaughter over a 22.4 week time period. Half of the pigs ate a diet based on conventionally grown corn and soy; the other half ate GMO corn and soy. The diets, other than the genetic difference, were designed to be as similar as possible. The GMO products were purchased from retail distributors, which means the scientists had little control over the nutritional composition of the feed. The contracts GMO food growers must sign forbid them from conducting research on the seeds.

In the study, the authors state that the U.S. has a voluntary system of studies conducted on these modified crops. And many regulators don’t require any studies on crops that contain “stacked” genes if all the genes in the stack have been individually approved. More than 37% of the GM corn varieties planted in the U.S. are stacked with both Ht and Bt traits that make the plants resistant to herbicides.

Ninety percent of the GMO corn used in this study contained a triple stack NK602, MON863 and MON810 genes. That corn produced three new proteins. Two protect the plant against insects, while the third provides the plant with tolerance to the herbicide glyphosate, used in Roundup. Roundup Ready soy was also used. The piglets were standard commercial Yorkshire-cross piglets obtained from a commercial facility.

When the piglets were 26 weeks old, they were fasted and slaughtered on two consecutive days. The internal organs were removed for study. Organ weights were not statistically different between the pigs fed GMO feed and non-GMO feed except for uterine weights. The GMO fed pigs had 25% heavier uteri, which is statistically significant. The study’s authors say the difference in uterine weights “warrants further investigation in future studies because such a biologically significant difference in uterine weights may reflect endometrial hyperplasia or carcinoma, endometritis, endometriosis, adenomyosis, inflammation, a thickening of the myometrium, or the presence of polyps.”

The other difference was in stomach inflammation. In non-GMO-fed pigs, stomach inflammation was in the “mild and moderate” range, while GMO-fed pigs had much more severe inflammation.

Pigs fed the GMO diet had 2.6 times the rate of severe stomach inflammation compared to non-GMO-fed pigs. While the authors acknowledge that the pig industry uses finely-ground feed, which can increase inflammation of the stomach, the study controlled the grind size, therefore removing it as a “confounder”. The authors think that an explanation for inflammation could be two proteins that the GMO corn varieties produce, called Cry 3Bb1 and Cry 1Ab, which act as insecticides.

The study concludes with the authors recommending that GMO crops destined for human food should undergo long-term animal feeding studies before commercial planting. And those studies should concentrate on toxicological and reproductive effects, especially since humans have a similar GI tract to pigs.

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