The study - published Wednesday in Food and Chemical Toxicology - found that rats who were exposed to Roundup, a weed killing herbicide, and rats who were fed Roundup-resistant corn developed mammary tumors, kidney and liver damage and died earlier than those in the control group.
According to the authors, this is the first study to examine the long-term effects of genetically modified Roundup Ready corn, or NK603, which is produced by biotech corporation Monsanto and has been approved for use in both the European Union and the United States.
Previous studies have examined the effects of NK603 on animals over the course of 90 days, while this study looked at a two-year period.
"There were no adverse effects in a 90-day feeding study on rats with NK603 maize grain..." says the EFSA GMO Panel in its scientific opinion on the corn. "The EFSA GMO Panel is of the opinion that maize NK603 is as safe as conventional maize. Maize NK603 and derived products are unlikely to have any adverse effect on human and animal health in the context of the intended uses."
The French study, however, found a series of adverse health effects in rats fed with the corn.
In this study, conducted on 100 female and 100 male rats, the animals were given either Roundup-resistant corn, the Roundup herbicide or both. Animals in all three of these test groups experienced adverse health effects and died earlier than rats in the control group, who were given regular corn and plain water.
"The results were really alarming," said Professor Gilles-Eric Seralini, co-director of the Risk Quality and Sustainable Environment Unit at the University of Caen, France and the study's lead researcher. Mammary tumors began to appear in females after 4 months, he said, and "after one year there was a high increase of a number of (kinds of) tumors. Almost every female rat had two or three tumors," said Seralini in a Wednesday press conference.
Up to 50 percent of males and 70 percent of females fed with GM corn died before their deaths could be attributed to normal aging, compared with 30 percent of males and 20 of females in the control group who died prematurely.
Tumors grew more frequently and rapidly among most test groups than among the control group. After 23 months, 50 to 80 percent of the treated female rats (percent depending on group) had developed tumors, while 30 percent of female control rats had tumors. The group treated with Roundup showed the greatest incidence of tumors. Of the females in this group, 80 percent developed at least one and up to three tumors.
Treated males developed tumors largely in their kidneys and skin, and were two times more likely to have a tumor during the 23rd month than control males. Treated males also suffered liver damage at greater rates.
"The results of the study presented here clearly demonstrate that lower levels of complete agricultural glyphosate herbicide formulations (such as Roundup), at concentrations well below officially set safety limits, induce severe hormone-dependent mammary, hepatic (liver) and kidney disturbances," write the authors.
Test rats were given varying doses of Roundup in their water and NK603 corn in their feed. The lowest doses administered in the study were lower than levels allowed in both the EU and U.S., according to the study.
The lowest treatment level of Roundup alone was at the "usual contaminating level of tap water," explained Seralini.
Test animals experienced severe adverse health effects even at these lowest levels.The authors say this result suggests that both products cause a hormonal imbalance.
"Our data show that, as is often the case for hormonal diseases, most observed effects in this study were not proportional to the dose of the treatment."
"This implies that both the NK603 maize and R(oundup) may cause hormonal disturbances in the same biochemical and physiological pathway," concludes the study.
The fact that groups treated with GM corn alone reacted similarly to those treated with the only the herbicide was surprising, says Seralini.
"We were really interested by the results of the GMO alone that was not treated with Roundup," said Seralini. "The groups with the GMO surprisingly also had hormonal disruptions and there were also mammary tumors."
After a detailed analysis of the chemical composition of the animals' diets, researchers found that two compounds in plants that protect animals against mammary tumors and toxicity of the kidney and liver were reduced to 51 percent with the consumption of the GM corn. They concluded that an enzyme that is over-expressed in 80 percent of GMOs was causing this effect, explains Seralini.
An estimated 70 percent of corn grown in the U.S. is Roundup Ready.
According to Monsanto's safety assessment, NK603 is corn into which DNA is inserted to make the plant resistant to the harmful effects of Roundup. Prior studies have shown that the CP4 EPSPS proteins expressed in Roundup Ready corn do not produce toxicity in mice, nor are they similar to known allergens or toxins, and they are rapidly digested in vitro.
Tom Sanders, head of the nutritional sciences research division at King's College London, expressed concern over the methods used in the French study.
"This strain of rat is very prone to mammary tumors particularly when food intake is not restricted," said Tom Sanders, head of the nutritional sciences research division at King's College London according to Reuters wire service. "The statistical methods are unconventional ... and it would appear the authors have gone on a statistical fishing trip."
Call to Action
The authors of the study, along with the Sustainable Food Trust - a nonprofit global group that promotes sustainable agriculture - say these results highlight a need to further supervise the approval and sale of genetically modified foods worldwide. The NGO stated the following in a press release Wednesday:
In light of these findings the Sustainable Food Trust sees the call to action as:
- A pre-cautionary review of the regulatory framework for testing Pesticides and GM foods
- The requirement for foods containing GM ingredients or their derivatives, or from animals fed on a GM diet, to be clearly labeled
- Further independent research exploring the potential human health effects of consuming these products.
The fact that GMO foods are not labeled in the U.S. is "in my opinion a very severe problem," said Seralini during the Wednesday press conference. Consumers should have the freedom to know what is in their foods, he says.
"In Europe we have this labeling and it enables us to avoid these compounds if necessary," he said.
This study comes just before California is set to vote on whether or not to mandate labels for GMOs, which will be on the ballot as Proposition 37 this fall.
"The results of this study are worrying," said Proposition 37 California Right to Know Campaign Manager Gary Ruskin in a statement Wednesday. "They underscore the importance of giving California families the right to know whether our food is genetically engineered, and to decide for ourselves whether we want to gamble with our health by eating GMO foods that have not been adequately studied and have not been proven safe."
Seralini says the results of his research also point to the need to test the effects of GMOs for two years - the average lifespan of a rat - rather than for 90 days, since the tumors found in this study appeared after four months had passed.
He also recommends that the U.S. government rely less on company tests when making regulatory decisions about the company's products.
The study was supported by the independent research organization, CRIIGEN and was published in the Food and Chemical Toxicology. It is available on the Sustainable Food Trust's website.
