Does Glyphosate cause breast cancer?

December 2019

Does glyphosate herbicide, sprayed on most GM crops and widely present in our bodies, cause cancer?

The answer is YES, but it's not that simple.

Cancer incidence continues to rise globally, with breast cancer being top of the list.

It's a difficult subject to study because cancer is rarely caused by one single factor. The picture emerging is that several cancer-promoting 'hits' co-operate to cause the disease. There's never going to be a simple substance-cancer link nor a dose-cancer relationship to any single material as used to identify a toxin.

Although the science is very much in its infancy, it's becoming clear that besides the genome (the easily engineered total compliment of DNA sequences), cells have an 'epigenome'. The epigenome is a whole layer of substances linked to the DNA. These substances attach in response to environmental and lifestyle factors, such as stressors, and alter DNA expression; they're vital to protect the balanced functioning of the genome, and their disruption leads to disease. Epigenetic changes are heritable along with the DNA structure, but are reversible.

Importantly, epigenetic attachments suppress the expression of genes which can cause a cell to become cancerous.

Assumptions promoted by the biotech industry that glyphosate must be safe for animals and humans because it targets biochemical processes only found in plants, have been translated by regulators into allowable levels of exposure.

While many scientists, medics and those affected by cancer have voiced concerns that glyphosate is a carcinogen, industry and government have been able to side-step the issue.

However, a study has now been published which not only induced model human breast cancers in 50 percent of mice tested, but identified the molecular mechanism.

The study used a state-of-the-art cell culture model which replicates different phases of cancer development. Human breast cells were modified to express a genetic control which is one of the 'hits' leading to cancer. These cells were exposed to glyphosate (the second 'hit'), and inserted into mice. Half of the mice went on to develop cancer.

It seems that glyphosate stimulates cells to produce a protein which strips off the protective epigenome. This won't, on its own, create a cancerous cell, but if a second pollutant is present to modulate regulatory factors in the unprotected genome, cancer genes will be activated.

The study raised a number of other serious concerns. For example, the experimental cells were model human breast cells which are known not to have any tendency to form tumours. Secondly, the level of glyphosate the cells were exposed to was very low, well below those detected in milk, blood, and urine in the general population, and thus completely relevant to common exposure levels. Also, the cells developed into a particularly aggressive form of cancer seen in younger women. Because the effect of glyphosate on the epigenome is global, long-term exposure will induce cumulative vulnerability of the genes with increasing risk of cancer.

Preliminary supporting studies have found a correlation between glyphosate exposure (as measured by urine levels) and loss of epigenetic attachments in breast tissue. The epigenetic mechanism identified may help explain the unexpected increase in mammary tumours found in a life-long study of rats fed glyphosate [1].

Suggested remedies for the glyphosate problem include a drug to inhibit the protein which strips the epigenome, vitamin supplements to maintain the epigenome, and limiting vitamin C intake to reduce epigenome degradation. The obvious way to reduce our cancer risk, by avoiding exposure to glyphosate in the first place, is not suggested by the authors.


This study is a game-changer: it has identified a clear mechanism for glyphosate to pre-dispose breast cells (and probably other tissues) to cancer. As the International Agency for Research on Cancer (IARC) concluded, glyphosate will probably give you cancer, especially if you are exposed to other carcinogenic 'hits', and who isn't? It begs the question, what are the chances that glyphosate is enabling the carcinogenic potential of a whole range of other pollutants with low allowable exposures?

Since the epigenome is heritable, glyphosate could be having continuing negative effects on future generations.

Note the authors' careful avoidance of offence to industry by suggesting drugs and artificial supplements (both profitable to big Pharma) as a solution. The idea of eliminating glyphosate, which would knock out most GM crops and biotech industry cash-cows, is not contemplated.

Industry will be desperate to sweep this study under the carpet. Draw both the study and the possibility of perverse reactions from Big Biotech to your regulator's attention.



  • Manon Duforestel, et al., September 2019, Glyphosate Primes Mammary Cells for Tumorigenesis by Reprogramming the Epigenome in a TET3-Dependent Manner, Frontiers in Genetics 10
  • Glyphosate can trigger aggressive breast cancer when combined with another risk factor, GM Watch 1.10.19
  • Can herbicides cause breast cancer? Purdue and INSERM scientists discover a piece to the puzzle,, 30.09.19

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