Herbicides stimulate antibiotic resistance

February 2018

Multi-antibiotic resistance in pathogenic microbes is a serious, and increasingly common, occurrence. It complicates the treatment of infectious diseases, makes health care more expensive, and can be a death-sentence for the patient.

We know that, once a pathogen evolves a mutant gene for antibiotic resistance, this can be passed to other microbes by horizontal gene transfer. Long ago, concerns were raised that the artificial antibiotic resistance genes often added to GM crop plants as markers during their development could fuel the emergence of antibiotic resistant pathogens. No one seems to be tracking whether this is a reality, but bugs can make themselves resistant to toxic medicines by other means, and counter-intuitively these 'other means' can be fuelled by herbicide-tolerant GM crops.

When bacteria are exposed to a toxin, their first line of defence is to switch on their own pumps to rid themselves of it. If this physiological mechanism can kick in fast enough (before the toxin kills it), the bug can make itself resistant to an antibiotic for as long as necessary.

The link to GM crops is that herbicidal chemicals and their spray co-formulants are also toxic to bacteria. Tests on the glyphosate-based herbicide used on most current GM crops, and on dicamba and 2,4-D which are up-and-coming replacements for glyphosate, plus the 'surfactants' added to all three to aid penetration into the weeds, showed they all trigger the toxin-pump mechanism in three commonly pathogenic bacteria. 'Surfactants' are detergents, classed as 'inerts' by US Environmental Protection Agency (EPA), and are ignored in safety assessments. However, the bacteria clearly don't find them 'inert'.

This creates a clinical problem because the bacterial toxin pumps aren't specific to the toxin that triggers them, be it a herbicide or a surfactant. If you're taking an antibiotic, the bugs it should be killing are already primed to pump the medicine back out, and you're not going to get any better.

While herbicide residue levels in commodity foods are set at 'safe' levels by regulators such as the CODEX Alimentarius Commission, other sources of exposure in both rural and urban settings aren't monitored. Our exposure to their accompanying surfactants is a complete unknown.

Then it gets worse.

If you eat lots of processed foods, that is the high-fat, high-sugar, food-like-substances which account for a substantial amount of GM 'food' in the US, you'll be eating significant quantities of emulsifiers added to 'improve' texture and extend shelf-life.

Emulsifiers are another form of detergent.

They've featured increasingly in our food chain since the mid-20th Century. On the same time scale, the incidence of Irritable Bowel Syndrome, obesity, type II diabetes, various chronic inflammatory diseases, atherosclerosis (a leading cause of heart disease and strokes) and colon cancer, have spiralled upwards. 

Science is linking dietary emulsifiers to unhealthy changes in our gut: in particular, altered microbe composition and diversity, toxin-production, thinning of the gut lining's protective mucus barrier, and penetration of gut microbes across the gut membrane. These changes are linked to gut inflammation, which has now been linked to cancer.

If you think that the artificial substances now so prevalent in the modern diet must have been thoroughly checked out, the reality isn't quite so black and white.

You can probably rest assured that neither those emulsifiers legally added to your food, nor those ignored pesticide surfactants which just happen to end up in your food and environment, won't cause you to drop dead.

However, it isn't reassuring to read that many additives (including emulsifiers) were given 'GRAS' (generally regarded as safe) status: this means little or no testing has ever even been considered. Nor is it reassuring to read in one published paper that permitted food emulsifiers are "probably largely broken down during the digestive process", when another describes two common food emulsifiers as "indigestible and mainly excreted in the faeces". Thus, in one version emulsifiers are portrayed as disappearing during their passage through the gut with unspecified break-down products, while in the other they remain intact so that the whole gut and gut microbial contents are exposed to them. A proportion of one emulsifier (possibly the only one ever tested) was found to make its way into the urine for excretion, suggesting the blood and kidneys are routinely exposed to it; the same emulsifier (possibly the only one ever tested) was shown to integrate into cell membranes.

Despite emulsifiers being detergents used because of their fat-dissolving properties, and despite the known fatty nature of the cell membranes, "there has been relatively little investigation of their possible effects on intestinal permeability".

'Polysorbates', a group of powerful emulsifiers which can be used effectively at very small concentrations in desserts and baked goods have been in our diet since the 1940s. At least one has been tested for carcinogenic potential and gave no cause for concern. A closer investigation reveals, however, that this testing goes back to regulatory approval in 1992. This was long before the links between gut flora changes, chronic inflammation and cancer were recognised. Modern testing might reveal some very different clinical properties in this additive.

The detergents in our food and environment may not be causing disease, but the data strongly suggest they create a 'favourable niche' for cancer of the colon, and contribute significantly to obesity and antibiotic resistance.

As put politely by one scientist, current testing "may be inadequate" (Chassaing).


Where there's been any testing at all, this has been on single detergents at realistic (very low) concentrations. It's clear the total interacting detergent load on our gut microflora and lining could be the major risk factor in modern chronic disease and be actively limiting our ability to treat infections. 

GM crops are designed to feed raw materials heavily sprayed with herbicides into the emulsifier-dependent processed food industry. Current testing is very much less than adequate, and far removed from the real-life situation. 

  • Brigitta Kurenbach, et al., 2017, Herbicide ingredients change Salmonella enterica SV. Typhimurium and Escherichia coli antibiotic responses, Microbiology Society
  • Emilie Viennois, et al., 7 November 2016, Dietary Emulsifier-Induced Low-Grade Inflammation Promotes Colon Carcinogenesis, Cancer Research
  • Benot Chassaing, et al., 5 March 2015, Dietary emulsifiers impact the mouse gut microbiota promoting colities and metabolic syndrome, Nature Letters 519
  • Carol L. Roberts, et al., 2010, Translocation of Crohn's disease Escherichia coli across M-cells: contrasting effects of soluble plant fibres and emulsifiers, Gut 59
  • Common Food Additive Promotes Colon Cancer in mice, Georgia State University, 2.11.16
  • Carol Torgan, Food additives promote inflammation, colon cancer in mice, NIH Research Matters, 22.11.16

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