Some scientists question GMO rat study

NPR - Some of their complaints about the study are aimed at the study's methods. Critics point out that the type of experimental rats used in this study are particularly prone to tumors. So if you divide up 200 of them into twenty groups, as this study did, you are likely to get very high tumor rates in some of the groups. And the fact that such clusters of tumors didn't show up in the two small control groups could easily be due to random chance.

One particularly irreverent critic, Michael Grayer, a medical statistician, pointed out that the study included 18 groups of rats that were exposed to GMOs or Roundup (nine each for male and female rats), compared to only two control groups. "The potential for cherry-picking the nice positive results here from a sea of boring null ones is immense," he wrote on his blog. "Not saying they did it, of course, but it's certainly a concern."Also, if this experiment truly showed a link between genetically engineered food and tumors, one might expect the rats that ate more of the GM corn to develop more tumors. In fact, the opposite happened. The rats eating a diet of 33 percent GMO corn stayed healthier than animals eating food with a GMO concentration of just 11 percent.