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Doubts on Séralini study linking GM crops and cancer

After the article published on Food and Chemical Toxicology, there was a lot of reactions by researchers and scientists. Efsa will next week deliver its preliminary review

A new study about linking GM crops and cancers was published 19 September on Food and Chemical Toxicology.
Researchers led by Gilles-Eric Séralini at the University of Caen in France announced evidence for a raft of health problems in rats fed maize that has been modified to be resistant to the herbicide Roundup. They also found similar health problems in rats fed the herbicide itself.

The health effects of a Roundup-tolerant genetically modified maize (from 11% in the diet), cultivated with or without Roundup, and Roundup alone (from 0.1 ppb in water), were studied 2 years in rats. In females, all treated groups died 2–3 times more than controls, and more rapidly. This difference was visible in 3 male groups fed GMOs. All results were hormone and sex dependent, and the pathological profiles were comparable. Females developed large mammary tumors almost always more often than and before controls, the pituitary was the second most disabled organ; the sex hormonal balance was modified by GMO and Roundup treatments. In treated males, liver congestions and necrosis were 2.5–5.5 times higher. This pathology was confirmed by optic and transmission electron microscopy. Marked and severe kidney nephropathies were also generally 1.3–2.3 greater. Males presented 4 times more large palpable tumors than controls which occurred up to 600 days earlier. Biochemistry data confirmed very significant kidney chronic deficiencies; for all treatments and both sexes, 76% of the altered parameters were kidney related. These results can be explained by the non linear endocrine-disrupting effects of Roundup, but also by the overexpression of the transgene in the GMO and its metabolic consequences.

This study was immediatly questioned by a lot of other scientists.

“All the comparisons are made with the ‘untreated’ control group -said David Spiegelhalter, Winton Professor of the Public Understanding Of Risk, University of Cambridge - which only comprised 10 rats of each sex, the majority of which also developed tumours. Superficially they appear to have performed better than most of the treated groups (although the highest dose GMO and Roundup male groups also fared well), but there is no proper statistical analysis, and the numbers are so low they do not amount to substantial evidence. I would be unwilling to accept these results unless they were replicated properly."

"Most toxicology studies are terminated at normal lifespan i.e. 2 years - said Prof Tom Sanders, Head of the Nutritional Sciences Research Division, King’s College London - Immortality is not an alternative. No food intake data is provided or growth data. This strain of rat is very prone to mammary tumours particularly when food intake is not restricted. There is a lack of information on the composition of the diet. One concern is whether there were mycotoxins in the maize meal because of improper storage. Zearalanone is a well know phytoestrogen produced by filamentous fungi that grow on maize. The statistical methods are unconventional, there is no clearly defined data analysis plan and probabilities are not adjusted for multiple comparisons."

The European Food Safety Authority (EFSA) will next week deliver its preliminary review of this new study. A multi-disciplinary task force set up by the Authority will analyse the paper by Séralini et al and publish an initial scientific review as the first step in a two-stage process.
If information gaps are identified, EFSA will then contact the authors with a request for further details of the methodology used in the two-year study.
The group of EFSA scientists from the GMO, pesticide and scientific assessment units are reviewing the study and may call upon additional external expertise if needed.
EFSA has been asked to consider the significance of the study’s findings as part of its ongoing remit to monitor scientific developments relating to its work.

by Alberto Grimelli
01 october 2012, Technical Area > Science News

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