Professor Parrott
highlights GMO articles that earn a failing grade
because the peer review system is not perfect, and some articles that shouldn't still get through

For more resources, see the GMO (mis)Information Page and Academics Review
GMO corn gives rats cancer

Source: Séralini GE, E Clair, R Mesnagea, S Gress, N Defargea, M Malatesta, D Hennequinc, J Spiroux de Vendômois. 2012. Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modifed maize. Food and Chemical Toxicology 50:4221–4231.

This article describes the results of an experiment whereby rats were fed corn, GM corn or corn with herbicide residue for two years. At the end of the feeding period, the rats eating GM corn or exposed to herbicide had higher tumor and mortality rates.

The main reasons --out of many-- why this paper fails:
  • The type of rats used is famous for getting tumours as they age. The tumor rate reported in this paper is within the normal tumor rate for this rat.
  • The experiment was designed for a 90-day study, not a 2-year study. Extending the duration of the study adds complications that were not accounted for.
  • The data and experimental details were not made public.
  • Inappropriate use of statistics; unequal sample sizes between treated and untreated animals.
  • In toxicology, cause-and-effect is established when there are more symptoms with higher doses; i.e., the dose makes the poison. Such a relationship was absent in the results.
  • Animal use and care ethical standards that require animals to be euthanized before tumors got too big were ignored- thus ensuring sensational photos were available.
  • When the statistics are corrected for multiple comparisons, as is standard, the negative effects disappear.
Additional expert assessments:
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