Can genetically modified maize cause cancer in rats?


Brief assessment from GenØk-Centre for Biosafety, 15 October 2012.

A recently published feeding study with genetically modified (GM) maize ( has shown increased occurrence of cancer and other illnesses in rats. This has caused a heated debate in many European countries.

Earlier feeding studies has only been performed within shorter time periods, with studies lasting from a few weeks and up to 90 days. This study was designed as a life-cycle study, which meant 2 years for some individuals. Particularly interesting in this study was that some effects seen in rats fed with GM maize were only apparent after 90 days.

The published study is unique as it is the first published life-cycle study with GM maize. It is important to assess the study’s scientific quality and methods. One weakness might be that in some groups the population was too small to compile a robust statistic. Some have criticized the choice of rats, claiming that this particular breed frequently develop cancer. One should therefore aim to repeat the study as soon as possible to confirm the results.

In risk assessments and approval of GM plants for use in food and feed, it is today required to publish data from 90-day studies. The observations made in the published study are therefore alarming and indicates that similar studies might have been too short. The conclusions relating to health risk in other studies might therefore have been made on insufficient grounds.

In order to improve food safety one should in the future include life-cycle studies in risk assessments and tests performed before the GM products end up in the supermarkets.