Update on Greenpeace Claim that Biotech Corn is a Mouse Contraceptive

Back in November I blogged about an Austrian government "study" that found that mice fed pest and herbicide-resistant biotech corn had fewer surviving babies. As I noted at the time:

(1) This is classic case of "science by press release." The "study" may be valid, but it has not been "published" nor has it been peer-reviewed; and (2) Greenpeace backed similar controversial claims by other researchers that genetically modified soybeans harmed the fertility of mice that were later debunked. (For more details see also here.)  

The July issue of Nature Biotechnology has a good news story about the how various European governments distort science in order to mollify the anti-biotech sentiments of environmentalist ideologues. The article updates where the Austrian mouse study stands:

…Jürgen Zentek and colleagues at the University of Veterinary Medicine in Vienna launched a feeding study in mice to assess health over generations. The aim of the study was to assess the health effects of a variety of GM corn carrying two transgenes-cry1Ab from Bt and the gene encoding 5-enolpyruvylshikimate-3-phosphate synthase from Agrobacterium sp. CP4 (CP4 EPSPS), which confers tolerance to glyphosate herbicides. Although the authors stated that "no negative effects of GM corn varieties have been reported in peer-reviewed publications," they wanted to assess health effects over several generations-something that has rarely been studied.

The researchers used three different experimental designs: a multigeneration study in which they bred laboratory mice over generations; a continuous breeding study in which they bred the same pair of mice and assessed the health of each subsequent litter; and a lifetime feeding study in which the health of mice fed the GM corn variety was compared to that of mice fed an isogenic (genetically identical) variety.

The only statistically significant finding came from the continuous breeding study. After the first litter, mice fed GM maize gave birth to fewer pups in each subsequent litter, and the average litter weights of pups in the GM group also decreased over time.

Although the results from the first arm of the multigeneration study (in which mice from each generation were bred with each other) were not statistically significant, the authors did report that the number of pups weaned, the average litter size and the weight at weaning tended to be lower in the GM group than in the group fed the isogenic maize variety. They also found that more pups died in the GM group. They reported that these differences were consistent over generations, but were not significant because the intragroup variability was very high.

The study, funded by the Austrian Ministry for Health, Family and Youth, wasn't published, nor was it peer reviewed. Rather, the results were announced at a press conference last fall. Greenpeace issued a press release touting the study: "Forget condoms-eat GM maize," read the headline. Other anti-GM groups also jumped on the news, and the internet was awash with stories touting the new study and its frightening findings. In its release, Greenpeace demanded a worldwide recall of all GM foods and crops, stating: "GM food appears to be acting as a birth control agent, potentially leading to infertility."

Monsanto, the producer of MON810 maize, almost immediately responded. Although they commended the study design, they criticized the data: "This report lacks sufficient experimental details to fully interpret the results and contains a number of errors that make it unsuitable for risk assessment and/or regulatory purposes," they announced in a press release.

Their criticism focused specifically on two major flaws. First, the authors did not use historical controls or reference groups throughout the study when comparing groups of mice. Without a proper control group of mice to assess natural variability in fertility, it's difficult to say how much of the fertility decline was caused by diet alone. In addition, the authors used inconsistent calculation methods, did not use standard units in some calculations and also miscalculated some data. And even when the calculations were corrected, the lack of a control group made the results impossible to interpret, Monsanto argued.

Monsanto's criticisms have been confirmed and elaborated upon by several scientists. At Monsanto's request, James Lamb, executive vice president of the Weinberg Group, a multinational regulatory consulting firm, wrote a review in which he concluded: "When properly analyzed, these data do not appear to support an effect on fertility or reproduction from consumption of GM corn". Lamb was the researcher who had originally developed the continuous breeding study design, at the Research Triangle Park, North Carolina-based U.S. National Toxicology Program during the 1980s.

But the authors aren't to blame, says Klaus Ammann, emeritus professor at the University of Bern in Switzerland. They are merely the latest victims of what has become the political gerrymandering of science to bolster and support anti-GM sentiment in Europe.

"The Austrian government had exhausted all legal avenues to ban cultivation of GM crops," Ammann says. "The Ministry of Health decided to avoid the peer-review process and announce study results at a conference, hide the data from scientists, and let the activists run amok with the help of uncritical media."

Indeed, in the ensuing months the Austrian government has backpedaled. The Ministry of Health responded to a request to interview Zentek or other authors with the following: "We asked the scientists to reevaluate their statistical analysis. Additionally the external evaluation will soon be started. I kindly ask you to wait with your proposal until the reevaluation is completed."

The mouse study is a prime example of governments' "misuse of science" to support political ends, says Jörg Romeis, an ecologist at the Agroscope Reckenholz-Tänikon Research Station in Zurich, Switzerland.

Of course, the mouse "study" is a success from the point of view of Austrian politicians since biotech corn is still banned in that country. I will let Reason readers know the results of the external evaluation when they are reported. 

I highly recommend reading the whole Nature Biotechnology article to get a better sense of to what lengths anti-biotech environmental activist groups will go to find and cherry-pick data to attack the overwhelming scientific consensus that current biotech crops are safe for people and the environment.