TWN Info Service on Biosafety
8 June 2026
Third World Network
www.twn.my
Dear Friends and Colleagues
Herbicides Used on GM Crops Cause Leaky Gut in Rats
In response to the spread of glyphosate herbicide-resistant weeds in GM agriculture, the agbiotech industry has developed GM crops tolerant to glyphosate plus 2,4-D and glyphosate plus dicamba.
A new study (Item 1) examined the effects of glyphosate and a glyphosate, 2,4-D, dicamba mixture on gut structure and function in rats. The study was designed to reflect two real-world chemical exposure scenarios: (1) exposure beginning prenatally in the womb and (2) a mixture of herbicides to which people, at least in the US, are increasingly exposed.
The study found that the glyphosate at “no observed adverse effect level” and the herbicide mixture “acceptable daily limit” doses resulted in gut dysbiosis – an imbalance in the composition and biochemical function of the gut, including the microbiome, and compromised integrity in both the small and large intestines (‘leaky gut’) – with the mixture showing the most severe negative impact. The leaky gut was caused by inflammation, oxidative stress, and alterations in the gut bacterial populations involved in the healthy functioning of the immune system.
Besides the public health implications, this study also has regulatory implications (Item 2). First, it adds to the growing body of evidence showing that the effects of chemical pollutants on gut structure and function should be included in regulatory safety studies. Second, chemical pollutants need to be evaluated for toxicity as mixtures and not only as individual agents. Additionally, the impacts of the herbicides used in conjunction with GM herbicide-tolerant crops should be considered in the evaluation of such crops.
With best wishes,
Third World Network
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Item 1
IMPACT OF GLYPHOSATE AND ITS MIXTURE WITH 2,4-D AND DICAMBA ON GUT BIOCHEMICAL FUNCTION, INTESTINAL BARRIER INTEGRITY AND MICROBIOME COMPOSITION IN ADULT RATS WITH PRENATAL COMMENCEMENT OF EXPOSURE
Mesnage, R., Ferguson, S., Nechalioti, PM. et al.
Arch Toxicol
https://doi.org/10.1007/s00204-026-04409-9
https://link.springer.com/article/10.1007/s00204-026-04409-9
28 April 2026
Abstract
Intensive use of glyphosate-based herbicides in genetically modified (GM) and non-GM agriculture has resulted in widespread glyphosate-resistant weeds. In response, the agricultural biotechnology industry has launched GM crops tolerant to glyphosate plus 2,4-D and glyphosate plus dicamba. Consequently, people are increasingly exposed to mixtures of these herbicides, yet no studies have been conducted to assess health risks. Intestinal structure and integrity, as well as gut microbiome composition and function, are recognised contributors to disease. Therefore, we investigated the effects of glyphosate alone and in combination with 2,4-D and dicamba on gut structure and function. Pregnant Wistar rats were administered via drinking water from gestation day 6 with glyphosate at the European Union (EU) no observed adverse effect level (NOAEL: 50 mg/kg bw/day) and acceptable daily intake (ADI: 0.5 mg/kg bw/day), and with an ADI mixture of glyphosate (0.5 mg/kg bw/day), 2,4-D (0.02 mg/kg bw/day) and dicamba (0.3 mg/kg bw/day). Offspring continued this regimen for 13 weeks post-weaning. Large and small intestinal tissues and gut content were isolated and analysed for inflammation, gut epithelial integrity, oxidative stress, microbiota composition and histopathology. The glyphosate NOAEL and, to a greater degree, the glyphosate, dicamba, 2,4-D mixture resulted in increased gut inflammation and permeability, associated with oxidative stress and altered microbial composition. Histological analysis confirmed structural alterations and inflammation in large and small intestine. Effects were more pronounced in large intestine and females. Our results identify exposure to glyphosate alone and a mixture of glyphosate, 2,4-D and dicamba as risk factors for gut structure and function dysbiosis.
[….]
Conclusion
This investigation provides important insights into the potential hazards to health posed by glyphosate and its mixture with dicamba and 2,4-D on gut structure, microbiota composition and physiological function. The observed alterations in inflammatory markers, barrier integrity, oxidative stress, and microbiome composition suggest a multifaceted impact on gut structure and function, including induction of compromised intestinal barrier integrity. These outcomes were more pronounced in the large intestine and female animals suggesting differential gastrointestinal tract region and sex sensitivity. However, further research is needed to elucidate the mechanisms through which these pesticides exert their effects on the gut, as well as potential long-term health risks. Our results are especially relevant to the US, which is experiencing a continuing increase in application of 2,4-D and dicamba along with glyphosate and consequent increased human exposure (Daggy et al. 2024; Gillezeau et al. 2020) with currently unknown health implications. In summary, our observations demonstrate that continued research is warranted to better understand the long-term implications of exposure to pesticide mixtures to human and environmental health.
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Item 2
HERBICIDE COCKTAIL USED IN GMO AGRICULTURE CAUSES LEAKY GUT
GM Watch
https://www.gmwatch.org/en/106-news/latest-news/20662
30 April 2026
In response to the spread of glyphosate herbicide-resistant weeds in GM agriculture, the agbiotech industry has developed GM crops tolerant to glyphosate plus 2,4-D and glyphosate plus dicamba, two other herbicides that glyphosate was originally meant to replace. As a result, people are increasingly exposed to mixtures of these herbicides, yet no studies have been conducted to assess the health risks of such chemical cocktails.
Intestinal structure and integrity, as well as gut microbiome composition and function, are recognised contributors to disease. Therefore, an international team of scientists, led by Prof Michael Antoniou, investigated the effects of glyphosate alone and in combination with 2,4-D and dicamba on gut structure and function.
The study was designed to reflect two real-world chemical exposure scenarios:
1. Exposure beginning prenatally in the womb
2. A mixture of herbicides to which people, at least in the US, are increasingly exposed.
The scientists have published their findings in a new paper which represents the most comprehensive evaluation to date of the effects of glyphosate and uniquely a glyphosate, 2,4-D, dicamba mixture on gut structure and function in rats.
In the study, Wistar rats were fed from day 6 of pregnancy with glyphosate at the EU “no observed adverse effect level” (NOAEL: 50 mg/kg bw/day) and “acceptable daily intake” (ADI: 0.5 mg/kg bw/day), and with an ADI mixture of glyphosate (0.5 mg/kg bw/day), 2,4-D (0.02 mg/kg bw/day) and dicamba (0.3 mg/kg bw/day). Exposure was then continued until 13 weeks post-weaning. The NOAEL is the dose in industry-sponsored animal studies that regulators conclude has no observed adverse health outcome. The ADI, calculated on the basis of the NOAEL, is the dose regulators assert is safe to consume on a daily basis over a lifetime.
However, the study found that the glyphosate NOAEL and the herbicide mixture ADI doses resulted in gut dysbiosis – imbalance in the composition and biochemical function of the gut, including the microbiome, and compromised integrity in both the small and large intestine (‘leaky gut’) – with the mixture showing the greatest negative impact.
The findings show that the levels of these herbicides, when ingested as a mixture, have adverse effects and are not safe at all – and that regulatory assurances of safety are false.
The findings in detail
Glyphosate and, to a greater degree, the glyphosate, dicamba, and 2,4-D mixture, resulted in increased gut inflammation and permeability (‘leaky gut’), associated with oxidative stress (an imbalance that causes cell and DNA damage) and altered microbial composition. Histological analysis confirmed structural alterations and inflammation in large and small intestine. Effects were more pronounced in the large intestine and in females. The results show that exposure to glyphosate alone and a mixture of glyphosate, 2,4-D and dicamba can cause gut structure and function dysbiosis.
Mechanistically, the findings indicate that the compromised gut integrity (leaky gut) was caused by inflammation, oxidative stress, and alterations in the gut bacterial populations involved in the healthy functioning of the immune system. The herbicide mixture caused a decrease in certain bacteria which are known producers of short-chain fatty acids, substances associated with a more balanced and anti-inflammatory gut environment. Overall, the shift in the bacterial population profile suggested the establishment of a pro-inflammatory condition.
Glyphosate alone at the ADI showed only some histological abnormalities but no biochemical effects, whereas glyphosate at the ADI combined with 2,4-D and dicamba, also at their respective ADIs, showed the most severe gut structural disruption and functional dysbiosis.
Lead author of the study Prof Michael Antoniou commented on the findings: “Our study has regulatory implications. First, it adds to the growing body of evidence showing that the effects of chemical pollutants on gut structure and function should be included in regulatory safety studies. Second, chemical pollutants need to be evaluated for toxicity as mixtures and not only as individual agents, as is currently practised by regulators in all nations.
“Our findings are particularly worrying for citizens of the USA, where there has been a massive escalation in the use of 2,4-D and dicamba along with glyphosate in recent years due to vast field infestation of glyphosate-resistant weeds and the subsequent launch of glyphosate/2,4-D/dicamba-tolerant GMO crops. Indeed, human biomonitoring studies in the US have shown a dramatic increase in urinary 2,4-D and dicamba levels since the introduction of these herbicide-tolerant GMO crops. Thus our findings have serious public health implications.”