This week saw another controversy in the media over the safety of genetically modified (GM) food. A group of researchers led by Gilles-Eric Séralini at the University of Caen in France published a paper in Food and Chemical Toxicology, claiming long-term health effects from Monsanto’s Roundup herbicide and from a type of GM Roundup-resistant maize. However, many scientists have criticised the authors for their experimental approach, overstating their conclusions and not providing sufficient statistical backing.
The authors reported that in lifetime feeding studies, rats fed on a diet containing NK603 Roundup-tolerant GM maize, or given water containing Roundup, died earlier than rats fed on a standard diet – suffering mammary tumours and severe liver and kidney damage.
It seems however, that the results are not as clear-cut as the authors asserted. Male rats that were fed on the highest doses of GM maize actually had lower death rates than rats that were fed a non-GM diet.
Among other criticisms of the study was the small number of rats used in each sample. Comparisons were made between different treatment groups which each comprised only 10 rats of a particular sex, making it difficult to draw conclusions.
“I do not think that the evidence presented in this study is sufficient to end [the GM] debate,” said Professor Rob Chilcott FSB, Head of Toxicology at the University of Hertfordshire and Chair of the UK Register of Toxicologists. “The limited number (10) of animals in each group fell well short of that required to provide a statistically robust analysis (generally considered to be 50 animals per treatment group). Furthermore, the incidence of tumours reported in the study for control and each treatment group were within the normal expected range for the strain of rat used.”
Alan Boobis, Professor of Biochemical Pharmacology at Imperial College London, added:
“Some of the effects are presented in a way that makes it difficult to evaluate their significance. For example, there does not appear to be a statistical analysis of the mammary tumours. These occur quite often in untreated animals.”
Dr Mark Downs, Chief Executive of the Society of Biology cautioned that the conclusions drawn from the report need to be considered in context.
“Studies to assess the safety of food for human and animal consumption are extremely important,” he commented. “However, it is difficult to draw any conclusions from the data in this study and the results need to be considered alongside the accumulated evidence on the safety of herbicides and GM plants.”
Professor Mark Tester, from the Australian Centre for Plant Functional Genomics at the University of Adelaide, added:
“The first thing that leaps to my mind is why has nothing emerged from epidemiological studies in the countries where so much GM has been in the food chain for so long? If the effects are as big as purported, and if the work really is relevant to humans, why aren’t the North Americans dropping like flies? GM has been in the food chain for over a decade over there – and longevity continues to increase inexorably!”
Monsanto responded to the publication by saying:
“This study does not meet minimum acceptable standards for this type of scientific research, the findings are not supported by the data presented, and the conclusions are not relevant for the purpose of safety assessment.
“Toxicologists and public health experts find fundamental problems with the study design. Critical information about how the research was conducted is absent, and the data presented do not support the author’s interpretations.”
Additional coverage of this story can be found at the following links:
Séralini et al. Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modiﬁed maize. Food and Chemical Toxicology 2012