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Do long-term studies on GM foods show they're safe?

In a courageous article in The Guardian, John Vidal reported on Seralini's new study, which found increased tumours, premature death, and organ damage in rats fed GM NK603 maize, and similar effects from tiny amounts of Roundup.

Vidal writes:

"This was scientific dynamite. It was the first time that maize containing these specific genes had been tested on rats over two years – nearly their full lifespan – as opposed to the 90-day trials demanded by regulators."
http://www.guardian.co.uk/environment/2012/sep/28/study-gm-maize-cancer

Vidal adds, "Around a dozen long-term studies of different GM crops have failed to find similar effects."

A GMWatch subscriber has written in asking if this last statement is true. As usual with claims of safety of GMOs, there's more to this story than meets the eye.

The review Vidal links to is much cited by GM pushers to claim GM foods have been found safe. It is this paper:
Snell, C., B. Aude, et al. (2011). "Assessment of the health impact of GM plant diets in long-term and multigenerational animal feeding trials: A literature review." Food and Chemical Toxicology.

The review looked at 12 long-term feeding studies (over 90 days, up to 2 years in duration) and 12 multigenerational studies (from 2 to 5 generations) on GM crops and concluded, "Results from all the 24 studies do not suggest any health hazards". 

However, many of these studies did find statistically significant differences in the GM-fed animals compared with non-GM-fed animals. Nevertheless the authors of the Snell review concluded, without further empirical investigation, that these were of "no biological or toxicological significance".

There's more about this unscientific dodge here:
http://www.earthopensource.org/index.php/3-health-hazards-of-gm-foods/3-1-myth-gm-foods-are-safe-to-eat (sections 3.1.2, 3.1.3, 3.1.4)

We must remind readers that this is precisely the same trick that industry and regulators used to release the toxic GM maize NK603 onto the market. Statistically significant findings of toxicity did show up in Monsanto's own 90-day feeding trial on the maize, as revealed by Prof Seralini's team's re-analysis of Monsanto's data:
de Vendomois, J. S., F. Roullier, et al. (2009). "A comparison of the effects of three GM corn varieties on mammalian health." Int J Biol Sci 5(7): 706 726.

But Monsanto and regulators dismissed these signs of toxicity without further investigation, with the result that we have all been exposed to this toxic maize.

The correct thing to do on finding such signs of toxicity in 90-day feeding trials is not to dismiss them as not biologically significant (a claim based on no evidence), but to extend the test to a longer-term period, or to several generations, or to look for more or different effects. Such detailed investigations will reveal what happens to the initial signs of toxicity, whether they go away, or develop into something else, or cause other knock-on effects. We are told that this would be required in the field of pharmaceuticals testing.

Extending the test to find out how preliminary signs of toxicity developed over time is just what Seralini did – and he found that NK603 caused tumours, premature death, and organ damage.

The dangers of relying on industry data – and interpretations of that data – in GM crop authorisations are illustrated by two other reviews of the scientific literature on the health risks of GM foods. 

These reviews demonstrate that the studies that claim safety are more likely to be industry-linked and are therefore inherently biased:

*A review of 94 published studies on health risks and nutritional value of GM crops found that they were much more likely to reach favourable conclusions when the authors were affiliated with the GM industry than when the authors had no industry affiliation. In the studies where there was such a conflict of interest, 100% (41 out of 41) reached a favourable conclusion on GMO safety.
Diels J, Cunha M, Manaia C, Sabugosa-Madeira B, Silva M. Association of financial or professional conflict of interest to research outcomes on health risks or nutritional assessment studies of genetically modified products. Food Policy. 2011; 36: 197 203.

*A literature review of GM food safety studies found that most studies concluding that GM foods are as nutritious and safe as non-GM counterparts were performed by the developer companies or associates.
Domingo JL, Bordonaba JG. A literature review on the safety assessment of genetically modified plants. Environ Int. Feb 4 2011; 37: 734 742.

More information is in Earth Open Source's report GMO Myths and Truths: 
http://bit.ly/SlOTdG

In spite of the fact that industry-linked studies have been shown to be biased, approvals for GM crops are based solely on such industry studies.