Glyphosate attack by stealth

February 2020

As pointed out before, there's a huge scope for current GM foods to impact on the microbes inside our gut and, along with that, our health [1].

Besides the novel nature of the foods themselves, there's the glyphosate-based herbicides sprayed on and accumulated by most commercial GM crops. Glyphosate blocks a vital biochemical pathway in green plants, but the pathway is also present in many bacteria. This suggests a very real possibility that the herbicide in GM foods could be devastating our health by stealth.

What is the science telling us about this?

Considering how many years we've been exposed to increasing glyphosate-based herbicides in our diet, it's taken a long time for the science to tell us anything.

A major difficulty has always been that many of the microbes in our gut won't grow independently in the laboratory and so can't be studied directly or quantified. However, now that we can screen samples using 'metagenomic analysis' (the identification of all the genes, and therefore potentially all the organisms present) and 'metabolomic analysis' (the identification of all the enzymes present which are driving biochemical pathways), we can start to work out what microbes are (or are not) present and what they are (or are not) doing.

A short, small-scale study has been published which used a rat model to demonstrate the sort of things likely to unfold in the mammalian gut and in the liver when there are glyphosate-based herbicides in the diet.

*Note.  Since most consumed glyphosate is excreted in the faeces, it's the contents of the gastro-intestinal tract which will be exposed to the highest concentrations of this herbicide.

The liver is the main organ of detoxification and the most likely part of the body to demonstrate an immediate reaction to something adverse in the diet.

These two organs are not independent: gut microbes and the liver are known to regulate each other by a reciprocal communication involving bile, anti-microbial substances, and dietary derivatives.

The rats were fed three concentrations of pure glyphosate or a common EU glyphosate formulation (MON 52276), the lowest being close to the EU allowable daily intake (ADI), and the highest being the US 'no-observed effects level (NOEL).

*Note.  US regulatory definitions of 'safe' levels of exposure to glyphosate are much higher than in the EU.

As predicted, the study found an accumulation of the biochemical intermediates of the pathway blocked by glyphosate. One of these substances has been implicated in gastro-intestinal tract cancer in animals and has been shown to stimulate proliferation in cultured human breast-cancer cells.

Also as predicted, the study identified increases in some bacterial types, one of which is found in the human gut and which includes species known to be pathogenic and to interfere with some drugs used for heart conditions.

Ominously, the study noted evidence of liver damage, including fatty-liver disease and dead tissue, and (although mostly not statistically significant) there was evidence of kidney dysfunction in the treated groups. What makes these indications disturbing is that, at the same time, the rats' blood biochemistry (our routine method of assessing liver or kidney disease) was little changed.

In light of the life-long (two-year) rat feeding study which also observed fatty liver disease in animals fed glyphosate but at a dose 120,000 times lower than in this short experiment, it can only be concluded that our current 'safety' tests are too brief, and our current analytical methods too crude to detect signs of harm from pesticides. Plus, our current 'allowable' 'safe' levels of exposure are way too high (and may even be zero).

As noted repeatedly in previous experiments, the formulation (which contains additives to increase glyphosate's toxicity in weeds) was more toxic to bugs than glyphosate alone.

A further major concern is that the microbes in the guts of the glyphosate-exposed groups were showing signs of stress and releasing 'protective' substances which have been linked to cell and DNA damage (both indicators for diseases such as cancer).

Metagenomics and metabolomics are in their infancy: such analyses haven't yet been standardised, and the implications of the alterations measured haven't yet been established. Considerably more research is needed into the mechanisms involved in the observed changes. However, as these results show, there's a wealth of important safety information within our grasp and waiting to be exploited.

Although rat gut microbes are substantially different from human ones, the authors anticipate that their findings will have relevance to human physiology.


This study is decades overdue: it involved just one agrichemical and just one out of hundreds of formulations in use. In the bigger picture, the damage to our health from modern agriculture is inescapable.

In Kenya, 6,000 youngsters are being trained in new agro-ecological farming techniques: they're discovering they can make a decent living (and protect their environment for future generations) without heading for the big city to look for employment.

It looks like the 'developed' world with all its resources and fancy technology could be left behind!

Check out




  • Robin Mesnage, et al., December 2019, Shotgun metagenomics and metabolomics reveal glyphosate alters the gut microbiome of Sprague-Dawley rats by inhibiting the shikimate pathway, bioRxiv preprint
  • Glyphosate and Roundup proven to disrupt gut microbiome by inhibiting shikimate pathway, GM Watch, 11.12.19
  • Glyphosate: Unsafe on any plate, Report by Food Democracy Now and The Detox Project, 2016
  • A farm with ZERO WASTE, Small World, Issue 69, Winter 2020
CC Photo Walter Baxter / Crop spraying at Rulesmains Farm, Duns

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