In terms of health there is a lot of different evidence, some of which is concerning. Unfortunately, Monsanto published a 90-day study in 2003 studying the effects of feeding GM (genetically modified) corn to chickens and didn't see any negative effects in the chicken breast muscle samples. Further, another 13 week study done in the U.S. on rats fed GM corn concluded that it did not see any significant differences between rats fed the GM maize versus the non-GM maize strain. However, upon closer inspection, of the results, it shows that red blood cell count and hematocrit (percent of red blood cells in the blood) SIGNIFICANTLY decreased for female rats fed the GM corn. Low red blood cell levels are associated with numerous adverse health outcomes leukemia, bone marrow cancer, kidney disease, and malnutrition, as well as many others. Therefore, this study did have a significant difference in the health of rats fed GM maize and it should have been noted. A systematic review concluded that most studies indicate that GM food may cause some common toxic effects such as hepatic, pancreatic, renal, or reproductive effects and may alter the hematological, biochemical, and immunologic parameters. Animal toxicity studies with certain GM foods have shown that they may toxically affect several organs and systems.
The most interesting study conducted however, was actually retracted from the Food and Chemical Toxicology journal. It’s raw data was re-published in the Environmental Sciences Europe Journal, so if you’re interested, check it out here. Dr. Seralini conducted a two-year feed study in rats, using the same rats that Monsanto used in their studies. He fed the rats genetically modified corn and the herbicide RoundUp that is typically sprayed on most foods and consumed by most individuals. On a side note, 88% of the corn grown in the U.S. is genetically modified, so chances are, if you’re consuming any corn products or anything that contains high fructose corn syrup, which most Americans are, you are inadvertently putting GMOs into your body on a regular basis. Anyways, back to Seralini’s study, all treatment groups (only GM-corn, GM-corn and Roundup, only Roundup) had significant chronic kidney deficiencies. In males, liver congestions and necrosis were 2.5 to 5.5 times higher than the control groups (which by the way, were fed the closest non-GM strain of this corn so that the varieties were not different). In females, all treatment groups showed a two- to threefold increase in mortality and deaths were earlier than the control group. Females developed large mammary tumors more frequently and before the controls.
There are even more specific results about the hormonal and physiological effect in the study, but the results I listed above are astounding. Obviously this is not a human model, but even so, it poses important questions about the use of GM-feed in animals, which humans are then consuming. Further, this study may correlate more closely to humans than we’d like to admit. A 2-year lifespan in a rat is about the midway point of a human life, around 35-45 and this is when we are seeing high rates of breast cancer spring up in women. Maybe the high rates of breast cancer (1 in 8 US women will develop invasive breast cancer in their lifetime) is linked to GMO use in our food supply in the last 25 years. Scary.
Overall, there is definitely more research that needs to be done, especially long-term studies in other animal models and in animal models that more closely model humans such as primates. As humans continue to consume GMOs and grow older, perhaps we may see if any negative health outcomes are associated with individuals who have high GMO consumption.