Evil Corn

For me, reading political blogs is akin to smoking – it’s a filthy habit. These days, I read largely for amusement because the amount and quality of actual information I glean from them is generally pretty small. And it soaks up more of my time than is really good for me. While it doesn’t justify the time I expend, I do run across a nugget from time to time. For example, here’s a tidbit about GM (genetically modified) foods breathlessly posted by Christy Hardin Smith over at Firedoglake. She’s alarmed because there may be some recent and preliminary evidence that corn modified to produce Bacillus thuringensis (Bt) toxin may produce infertility in mice, and therefore we’re all going to become sterile. Per standard operating procedure with ideologues who slice the world into good guy/bad guy narratives (GMOs = Monsanto = BAD), the post was thin on details, but there was a trail of breadcrumbs pointing to some richer sources of information which looked interesting enough to break my blogging fast. As I peeled this onion, I found that this issue has more complexities which, if you want to do more than foam at the mouth about how evil Monsanto is, need to be explored and incorporated into the policy discussion. For now, I’m going to pass on commenting on her subsequent handwringing about linkages of Bt corn and infertility with reproductive health risks associated with endocrine disrupting chemicals. The liberal blognoscenti can get educated about cumulative risk assessment some other time.

Gourmet magazine online has more of the story on Bt corn here. The Center for Food Safety press release has a link to the study. The study itself is published by the Austrian Federal Ministry for Health, Family and Youth, which is responsible for regulation of genetically-modified organisms under European Union directives. There, that wasn’t so hard was it? I’m not going to demand that folks wade through the entire 105 page report, but they could at least struggle through the page and a half executive summary.

The researchers fed mice a diet of 33% genetically modified corn which produces Bt toxin along with control groups fed 33% non-genetically modified corn. Two different kinds of reproductive studies were performed, a multi-generation study where the mice were fed GM (or non-GM) corn and bred over four successive generations, and a “reproductive assessment by continuous breeding” where the same generation of mice were fed GM (or non-GM) corn but delivered four successive litters. These studies were designed to identify reproductive hazards, and don’t directly reflect the risks associated with the patterns or levels of consumption of GM corn by humans (this kind of work is combined with other research to address those questions).

The multi-generation study is probably inconclusive; the differences in numbers of offspring between the GM and non-GM groups were not considered to be statistically significant. The experimental design involved 24 breeding pairs of mice per study group. Would larger study groups produce more statistical power? The “reproductive assessment by continuous breeding” (RACB) study showed significantly reduced numbers of offspring in the mice fed GM corn. The investigators state that the multi-generation study design is less physiologically demanding on the animals compared with the RACB design – suggesting that the RACB study might have been more sensitive.

The Austrian investigators did some admittedly cool genomic testing, which reportedly identified some differences in metabolic pathways between the GM and non-GM mice. This kind of genomic testing is in its infancy, so there isn’t a lot of experience in how to use the data. But many feel there’s a lot of potential value in genomic techniques.

Monsanto questions these results, noting the overall higher offspring mortality in both the GM and control (i.e. non-GM) groups in the RACB study, and pointing to flaws and limitations in the presentation of the results. Its position is that when the results are correctly interpreted, they don’t indicate a reproductive effect. Monsanto also questions the data quality of the genomic testing as well as the interpretation of the results.

This is as it should be. Think what you will of Monsanto, but I found its comments a useful counterpoint in my understanding of the Austrian study. Monsanto might have a fair criticism in blasting the Austrian government by doing science by press release. When you do that, someone with a megaphone, who might not worry over the details, is bound to broadcast the wrong message. The question people should be concerned about is not “is GM corn in my food going to make me sterile”, but rather why we are examining long-term reproductive effects of genetically modified foods, consumed by hundreds of millions of people, years after they’ve been introduced into the foodchain.

However, solving that puzzle requires revisiting the history of the safety assessment of GMOs, and is just going to have to wait for another day (that blogging versus day job tension again).

Footnote: there’s a nice primer on genetically modified Bt corn over at the Science Creative Quarterly, published by the University of British Columbia.