Very few long-term studies into the potential health impacts of GM crops have been carried out. The rat feeding studies conducted by the GMO industry to support regulatory authorization rarely extend beyond 90 days,[1] [2] a subchronic period[3] that is not able to detect long-term (chronic) health effects. Indeed, the European Food Safety Authority (EFSA) has argued against the need for trials longer than 90 days.[4]

Ninety days in a rat is equivalent to only around 7 years in human terms, based on the 3-year average natural lifespan of a laboratory rat.[5] Two years, the length of Séralini’s study, is two-thirds of the natural lifespan of a rat, mirroring the long-term exposure of people to GM food crops.

A search conducted by the French food safety agency ANSES for long-term studies comparable to the Séralini study and focusing on commercialized glyphosate-tolerant GM crops identified a grand total of two studies. Neither was performed by the GMO developer company prior to commercialization of the GMO.[6] One found toxic effects from feeding GM soy to mice[7] and the other is only available in Japanese and cannot be evaluated by the international scientific community.[8]

Even industry’s short 90-day studies have generated evidence of statistically significant early impacts of GM crops on multiple organ systems,[9] [10] indicating the need for longer studies.

GMO proponents often cite a review examining the results of 24 long-term studies to show GMOs are safe to eat over the long term.[11] However, this claim is misleading. The 24 studies do not provide evidence for the long-term safety of commercialized GMOs for human consumption, since they include:

1.    Studies that found toxic effects and signs of toxicity in the animals fed a GM diet, which are dismissed by the review authors as being of “no biological or toxicological significance”

2.    Studies in which the animals eat the GM diet for only a small proportion of their natural lifetime and which are therefore not long-term at all

3.    Animal production studies on livestock, which do not examine health effects in detail but focus on effects of the GM diet on issues of interest to farmers, such as weight gain and milk yield

4.    Studies on animals with a different digestive system and metabolism from humans, such as cows and fish

5.    Studies carried out by GMO industry-sponsored authors, which can be biased.

Moreover, the authors of the review use unscientific double standards to dismiss studies that find toxic effects and signs of toxicity from GM feed, while accepting at face value only those studies that conclude the GM feed is safe.

The review’s conclusion that “GM plants are nutritionally equivalent to their non-GM counterparts and can be safely used in food and feed” is not justified by the evidence provided. In fact, some of the studies present evidence that GM plants are not safe to eat.

Given the lack of long-term safety research on GMOs, Séralini’s study offers rare and valuable data on this important public health issue. A limited sampling of study results is reported in Séralini et al (2012), with further results from this large trial expected in forthcoming papers.


[1] Séralini GE et al (2010). Possible negative health impacts due to holes in assessment: Overview of the safety studies of GMOs performed on mammals. Implications of GM-Crop Cultivation at Large Spatial Scales. B. Breckling and R. Verhoeven. Frankfurt, Peter Lang.

[2] Séralini GE et al (2009). How subchronic and chronic health effects can be neglected for GMOs, pesticides or chemicals. Int J Biol Sci 5(5): 438-443.

[3] Organisation for Economic Cooperation and Development (OECD) (1998). OECD guideline no. 408 for the testing of chemicals: Repeated dose 90-day oral toxicity study in rodents: Adopted 21 September 1998.

[4] European Food Safety Authority (EFSA) GMO Panel Working Group on Animal Feeding Trials (2008). Safety and nutritional assessment of GM plants and derived food and feed: The role of animal feeding trials. Food Chem Toxicol 46 (Suppl 1): S2-70.

[5] SAGE Research Labs (2014). Sprague-Dawley outbred rat.

[6] ANSES (2012). Opinion concerning an analysis of the study by Séralini et al. (2012) “Long term toxicity of a ROUNDUP herbicide and a ROUNDUP-tolerant genetically modified maize”. 19 Oct.

[7] Malatesta, M., et al (2008). A long-term study on female mice fed on a genetically modified soybean: effects on liver ageing. Histochem Cell Biol 130: 967–977.

[8] Sakamoto, Y., et al. (2008). [A 104-week feeding study of genetically modified soybeans in F344 rats]. Shokuhin Eiseigaku Zasshi [Journal of the Food Hygienic Society of Japan] 49(4): 272-282.

[9] Séralini GE et al (2011). Genetically modified crops safety assessments: Present limits and possible improvements. Environmental Sciences Europe 23(10).

[10] Séralini GE et al (2007). New analysis of a rat feeding study with a genetically modified maize reveals signs of hepatorenal toxicity. Archives of Environmental Contamination and Toxicology 52(4): 596–602.

[11] Snell, C., et al. (2012). Assessment of the health impact of GM plant diets in long-term and multigenerational animal feeding trials: A literature review. Food and Chemical Toxicology 50(3–4): 1134-1148.

[11] Snell, C., et al. (2012). Assessment of the health impact of GM plant diets in long-term and multigenerational animal feeding trials: A literature review. Food and Chemical Toxicology 50(3–4): 1134-1148.

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