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2013 articles

A scientist responds to criticism of the Séralini study

on .

People need to stop falling for the constructed myth that Seralini's study was a flawed carcinogenicity study, says a scientist.

Some commentators on the Seralini study retraction, including Seralini himself, have called for retraction or re-evaluation of Monsanto's 90-day rat feeding studies on its own GMOs from the journal Food and Chemical Toxicology.

Critics of the Seralini study have replied with arguments that can be summarised as follows:

"There are several flaws in the experimental design of Seralini's experiment and reasons why the conclusions are not valid. It is misleading to compare the 90-day Monsanto studies with Seralini's. The Sprague Dawley strain of rat is appropriate for a 3-month toxicity study but not for Séralini's long-term two-year one because they tend to develop spontaneous tumours at over 18 months of age. This natural tendency creates experimental noise. The only way to annul this experimental noise is to make the sample sizes much larger, so that robust statistical tools can be applied. This is a fundamental flaw in Seralini's paper."

We've had a lot of requests to obtain a specific scientific response to such criticisms. Here it is, from an experienced research scientist:

"The arguments that Seralini used too few SD rats for a two-year study and that the Sprague-Dawley (SD) strain is inappropriate for a two-year carcinogenicity study are irrelevant.

"The mistake these critics make is that they think Seralini set up this investigation as a carcinogenicity study, which he did not. If they read the paper properly they will see stated in the introduction that this was a toxicity study, which quite unexpectedly happened to see an increase in tumour incidence in treatment groups. The principle aim and findings of the study have to do with multiple, and especially liver and kidney, organ pathologies, which peaked during the second year (at 15 months) of life. For this type of investigation there were sufficient animals in accord with OECD industry guidelines. And the SD rat is routinely used for chronic toxicity AND long-term carcinogenicity studies both by industry and academia.

"There were perhaps too few animals for a carcinogenicity study (which, however, this was not). Therefore the higher tumour incidence seen in some test groups may be due to random variation and within the background levels of fluctuation, due to high spontaneous tumour incidence rates. So to be sure about the tumour findings, a full-scale carcinogenicity study needs to be performed with larger numbers of animals.

"However, the differences between control and test groups in Seralini's experiment were so large that even the relatively low numbers used here are informative as to harm: e.g. only ONE male control animal developed a tumour late in life compared to 3-4 in test groups, and only three control females showed tumours, with up to three times this number in some test groups.

"People need to stop falling for the deliberately created myth that this was a flawed carcinogenicity study and see it for what it really is: a toxicity study giving highly statistically significant differences in organ pathologies. The focus on the tumours in the media is misleading in this regard, but Seralini's actual paper does not mislead or overstate the conclusions."

For more detailed rebuttals of criticisms of the study, see gmoseralini.org.