Glyphosate and cancer

September 2013

Crop spraying. Photo Oliver Dixon [CC-BY-SA-2.0
(], via Wikimedia Commons
French professor, Gilles-Eric Séralini, has trodden firmly on regulatory and biotech toes on more than one occasion.

In 2007, he mentioned the taboo words 'endocrine disruption' in his re-analysis of the safety data submitted by Monsanto on its MON683 GM maize to the European Commission.

This was followed by a number of publications critical of the superficial nature of existing risk assessments for GM crops, and adding further evidence on endocrine effects.

In 2012, Séralini published experimental results suggesting that GM herbicide-tolerant maize, NK603, and the 'Roundup' herbicide used with it are linked to increased mammary tumours in susceptible animals (see GM MAIZE IS NOT SAFE TO EAT - October 2012).

With the incidence of newly-diagnosed breast cancers running at nearly 50,000 per year in the UK, Séralini's findings have to be taken seriously.

Much concern has already been voiced that a significant factor in our cancer epidemic is the modern exposure to endocrine-disrupting chemicals in our food and environment. The suggestion that GM food could exacerbate the problem was not welcome.

More science is clearly needed to establish cause-and-effect. However, a paper published in 2013 added another piece to the GM-risk jigsaw.

A team of scientists in Thailand found that glyphosate, the active ingredient of Roundup herbicide, stimulated the growth of certain types of human breast cancer cells. The mechanism was identified as being the same as that of genistein, a key phyto-oestrogen found in soya. Importantly, the effect of the two together was additive.

Human breast cancers which are hormone-dependent comprise about 70% of the total. They may not be caused by phyto-oestrogens, but exposure to endocrine-disruptors could well be a factor in the disease becoming catastrophic.

The study was based on model human cancer cells in culture. A real-life situation would be more complex, with more interacting factors pushing the disease out of control. For example, the extra stimulus to cell growth induced by several endocrine disruptors can be additive, as was found in the case of glyphosate and genistein, but the effects could also be synergistic, meaning that very low levels of substances measured as 'safe' when they present individually, could cause havoc when presenting together.

Several supporting studies are cited by the authors. These include synergistic effects between glyphosate and two forms of oestrogen, and the repeated finding that formulated herbicides (such as Roundup) which contain glyphosate, are more toxic than glyphosate on its own as used in their experiment.

Interestingly, the phyto-oestrogen profile of organic soya has been found to be very different from both conventional and GM soya. In particular, genistein seems to be a less significant constituent of organic soya beans. GM soya with its glyphosate load plus its higher levels of genistein could significantly increase the risk of cancer in susceptible individuals.


Courtesy of glyphosate-tolerant GM crops and the increased spraying needed to combat the surge of herbicide-tolerant super-weeds, global exposure to glyphosate in increasing year on year.

Ask our regulators to get their heads out of the sand and consider very seriously the endocrine-disrupting effects of glyphosate. The incidence of breast cancer (in males as well as females) could get much worse.

  • Siriporn Thongprakaisang et al., 2013, Glyphosate induces human breast cancer cells growth via estrogen receptors, Food and Chemical Toxicology, June
  • L. S. Santos, 2006, Chemotaxonomic markers of organic, natural, and genetically modified soybeans detected by direct infusion electrospray ionization mass spectrometry, Journal of Radioanalytical and Nuclear Chemistry, 269:2
  • Gilles-Eric Séralini et al., 2012, Long term toxicity of a Roundup herbicide and a Roundup-tolerant genetically modified maize, Food and Chemical Toxicology, on-line August 2012
  • Gilles-Eric Séralini 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
  • Cancer statistics for 2010
  • Estrogen receptors,

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