Long Term Effects of GM Maize and Roundup on Rats

Genetic modifications to crops raise many concerns about possible health threats to humans and other animals. Extensive testing is required to show that a particular modification does not produce a substance or alter a biological process that may lead to health concerns for consumers. While studies of this nature have become commonplace, results are hardly consistent across the board, and truly long-term procedures are rare. Séralini et al. (2012) conducted an experiment to measure the effects of both Roundup-tolerant maize feed and the herbicide Roundup itself on rats over a two year time span, using many different concentrations and variations of these variables. The researchers find that rats exposed to GM maize feed and/or Roundup herbicide demonstrate higher levels of tumor development as well as earlier death as compared to control groups. However, most of their results are of limited impact due to statistical insignificance.—Chad Redman
                  Séralini, G. E., Clair, E., Mesnage, R., Gress, S., Defarge, N., Malatesta, M., Hennequin, D., Vendomois, J. S., 2012. Long Term Toxicity of a Roundup Herbicide and a Roundup-Tolerant Genetically Modified Maize. Food and Chemical Toxicology 50, 4221–4231.

                  Séralini et al. raised 200 rats over the span of two years, 100 males and 100 females. For feed, the researchers grew three distinct plots of maize, one being an isogenic, non-GM strain, one being Roundup-tolerant but not sprayed with Roundup, and the other being Roundup-tolerant and sprayed regularly with Roundup. In order to test for adverse effects of both the genetically modified Roundup-tolerant maize and the herbicide Roundup itself, both the males and females were randomly separated into ten distinct treatment groups. Six of these groups were fed the GM maize, three the Roundup treated stock and three the untreated stock. For each stock, three different diets were fed, one group a diet of 11% maize, another group a diet of 22% maize, and the third a diet of 33% maize. In addition, these rats were given access to plain water. The next three groups of rats were fed non-GM maize diets, but given water containing differing concentrations of Roundup; the three percentages of Roundup in the drinking water, by weight, were 1.1 x 10–8%, 0.09%, and 0.5% Roundup. Finally, each sex also had a control group of ten rats that were fed isogenic maize and plain water. These rats were kept in tightly controlled conditions at a comfortable temperature and humidity, a twelve hour light-dark cycle, and absolutely consistent feeding patterns.
                  The findings of Séralini et al. are interesting and somewhat alarming. Average lifespans of the rats were determined to be 624±21 days for males, while the females lived an average of 701±20 days. The mortality rate of rats that were outside of the control group was generally higher, and the first rats that died over the course of the procedure were males in the groups fed GM maize. Unfortunately, it is unclear if the differences observed in time of death for control rats versus any of the test group rats were statistically significant. Nonetheless, the trend is easily observable that rats in the control groups lived the longest. As for specific tissue testing and tumor development, the rats had blood, urine, and after death, organ samples taken and tested for nutrient content and cell structure similarity. Here again, the researchers failed to establish statistical significance with their data. Trends show that test groups, especially females, developed oddities in cell structure as well as demonstrating high propensity for tumor development. In short, although these researchers presented interesting data and conducted a thorough, long term experiment on the health risks of GM maize, they fall short on making a groundbreaking discovery because the observed trends were not statistically significant.

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