Source: Ewen SW, A Pusztai. 1999. Effect of diets containing genetically modified potatoes expressing Galanthus nivalis lectin on rat small intestine. Lancet 354(9187):1353–1354.
This is the original GMO junk science paper on the food safety side. In this experiment, the authors used potatoes engineered to produce lectin, a known toxin (but which is *not* used in commercialized GMOs), and fed them to rats. A control group was fed conventional potatoes.The study was designed so that the investigators could separate out the effects of the lectin from other effects. After doing so, they were left with additional intestinal changes in the GM-fed rats. At this point, rather than looking for other causes, the investigators decided that something unknown and unintended about the process itself of creating a GMO was causing the differences.
Yet, glycoalkaloids, known to be toxic to monogastric animals were not measured in the potatoes used for feed. For that matter, the Royal Society (1999) noted that other components of the diet were not measured either, the sample size was too small, there were possible dietary deficiencies in the group fed the GE potato, the results were not consistent across treatments, and the statistical treatment used was inappropriate.
The main reasons why this paper fails:
- It is well established that even small dietary changes can have large effects. Thus, feeding studies are very difficult to conduct, as every little detail must be kept the same, except for the presence or absence of the engineered gene. In this particular study, the nutrient value of GM and non-GM diets were assumed to be the same, but never measured. Furthermore, potatoes produce glycoalkaloids, chemicals which are known to irritate the digestive system, even at low doses. It is therefore impossible to attribute intestinal disorders to the genetic modification process.
- Even if the investigators were correct in that there was some unintended effect from the engineering process, the fact remains that the potatoes used in this experiment had not been through the safety evaluations that GM crops undergo prior to commercialization. These safety tests include extenstive compositional analyses which are conducted to ensure nothing unexpected is produced.
- When the statistics are corrected for multiple comparisons, as is standard, the negative effects disappear.
Additional expert assessments:
- The Royal Society – Review of data on possible toxicity of GM potatoes
- Academics Review – Pusztai’s flawed claims