Controversial study linking genetically modified corn to cancer under attack by scientists

A recent study published in the peer-reviewed journal Food and Chemical Toxicology is indicating that rats fed on GM maize have a significantly heightened risk of developing tumors. In turn, the French government has asked a health watchdog to conduct an investigation, possibly leading to an EU-wide suspension of the Monsanto product. But the study has also instigated a firestorm of criticism, with many scientists complaining that the results are completely unreliable.

First, the study. European researchers conducted a two-year experiment in which 200 male and female rats were split into 10 groups (including a control). Three groups were given conventional rat food with increasing doses of the herbicide, Roundup (reflecting its presence in the food chain). The other groups were fed rat food which contained Monsanto's NK603 corn, and in amounts of 11, 22, and 33% (with controlled and variable levels of Roundup).

What they discovered was that the GM maize and the herbicide both caused similar damage to the rats' health (when consumed together or alone). Females were particularly susceptible, leading to sickness and premature deaths. When the experiment reached the 14-month stage, females developed cancer at a rate of 10 to 30%. At the same time, none of the mice in the control groups showed any signs of cancer. And by the end of the experiment, 50-80% of female rats had developed tumors in all treated groups (with up to three tumors per animal), whereas 30% of controls were affected. Of the males who got sick, they experienced liver damage, kidney and skin tumors, and digestive problems.

So, that's the study. And as noted, it did pass through peer-review. But that hasn't stopped the onslaught of criticism — something the French researchers are well accustomed to by know; their seemingly anti-GM studies have been criticized in the past.

After speaking to several scientists, Emily Sohn of Discovery News reports:

One immediate problem, [Martina] Newell-McGloughlin said, is that the line of rodents used in the study, known as Sprague-Dawley rats, are frequently used in cancer research because a large majority of them naturally develop tumors at a high rate, regardless of what they eat or how they're raised.

What's more, the rats were allowed to eat an unlimited amount of food, which increases their chances of developing tumors. And two is a very old age for these rats, which could account for the large rate of cancer seen across all groups, including the controls.

The small size of the control group also raised red flags. Even experienced scientists in the field had trouble interpreting data in the study, as seen in comments collected by the UK's Science Media Center, but it appears that the study included just 10 or 20 control animals.

That means there were at least nine times more test animals than control animals. If anything, studies of this kind usually include two or three times more controls than experimental animals.

The results don't make a lot of sense, either. No matter how much of either herbicide-laden or genetically modified maize the rats ate in proportion to their other food, rates of cancer and premature death remained the same. However, to be meaningful, toxicology studies like this should show a dose-dependent response, which means that if something is toxic, more of it should be more toxic.

Sohn also notes microbiologist David Tribe's complaint that the researchers did not account for random effects, and that rats are ill-suited for such short-length investigations.

Over at Forbes, Tim Worstall has put together a comprehensive list of criticisms from various scientific circles, many of which complain about the methodology used, the deliberate use of unsightly pictures of tumor-ridden rats, and the potential (hidden) political agenda of the researchers (one of whom is a homeopath).

It certainly appears that the study has its problems, and that the proliferation of the researchers' findings in the press will cause a lot of problems for Monsanto, while potentially giving the public a false sense of the dangers of GM corn.

More to the point, however, this episode also shows that peer-review ain't always what it's cracked up to be. Oftentimes, where there's a will to get something published, there's a way.

As a last note, what needs to happen now is for an independent research group to corroborate or disprove the study. Words are just words; what's needed is due dilligence and the presentation of more meaningful data to settle this once and for all. Given the stark implications of the study's findings, this is only common sense.

Other source: France24. Image: Madlen/Shutterstock.com