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Glyphosate, a broad-spectrum herbicide and the active ingredient in many popular weed killers, has gained notoriety for its potential hazards to human and animal health. Ever since its introduction in the mid-1970s, the controversy surrounding glyphosate has expanded from the science labs to the courtrooms.1 Our goal is to delve into these dangers, focusing particularly on how glyphosate contributes to “leaky gut,” thus leading to further gastrointestinal issues.

The Leaky Gut Connection

Gut health is foundational to overall health. A well-functioning digestive system acts as a barrier, allowing nutrients to enter the body while keeping harmful substances out. However, this barrier can be compromised leading to a condition known as intestinal permeability, or more commonly, ‘leaky gut.’

Gut barrier disruptors – of which glyphosate is suspected of being – are manmade compounds with the capability of damaging the intestinal epithelial barrier.2 The theory is that not only will this lead to a leaky gut, but also increase the uptake of allergens and other foreign substances into the bloodstream, resulting in an inflammatory response by the immune system. Ongoing exposure to glyphosate and/or other chemical herbicides and pesticides could result in food allergies and systemic inflammation, which can create a bevy of gastrointestinal and other health problems.

In addition to compromising the intestinal barrier, glyphosate has been shown to negatively affect the microbial composition of the gut microbiome (i.e., dysbiosis, or imbalance). Initial research with chickens showed that highly pathogenic bacteria, such as Salmonella Entritidis, Salmonella Gallinarum, Salmonella Typhimurium, Clostridium perfringens, and Clostridium botulinum, were highly resistant to glyphosate. Conversely, most of beneficial bacteria, such as Enterococcus faecalis, Enterococcus faecium, Bacillus badius, Bifidobacterium adolescentis, and Lactobacillus spp. were either moderately or highly susceptible to glyphosate.3 Glyphosate ingestion disturbed the normal bacterial composition in the gut via a reduction of beneficial bacteria.

More recently in 2022, an analysis found similar results by studying the human gut microbiome. Fifty-four percent of the most common bacteria living in the human gut are sensitive to glyphosate exposure.4 Some of the same species of bacteria analyzed have previously been shown to play a role in irritable bowel syndrome (IBS). Experts speculate that the increased prevalence of dysbiosis and gastrointestinal issues coincide with glyphosate exposure which has become synonymous with the Standard American Diet, and Western diets generally.

Broader Implications of Glyphosate Exposure

Beyond gut health, glyphosate exposure has broader implications for both human and animal health. It has been associated with an increased risk of various cancers, particularly non-Hodgkin lymphoma.5 In the agricultural context, glyphosate residues have been detected in pet food, and this can, in turn, negatively impact the health of our companion animals. One study found that pet food could expose animals to glyphosate amounts 4-12 times higher than that of humans.6

The potential ecological impacts of glyphosate use are also concerning. Glyphosate can harm non-target species, including beneficial insects, soil microbes, and amphibians7. These ecological effects have ripple effects on the health and stability of entire ecosystems. Many of these pathways lead directly back to humans.

Currently, much of the research involves animal models because it would be unethical to intentionally subject humans to glyphosate (outside of normal dietary exposure). Mouse studies have shown that glyphosate altered the normal gut microbial composition by reducing both abundance and diversity.8 Specifically, it led to a decrease in Firmicutes, Bacteroidetes, and Lactobacillus, which was then correlated with an increase in anxiety and depression-like behavior. Although by no means a cause and effect, it should be noted that there has been a significant uptick in anxiety, depression, and other mood disorders in humans.

Rats chronically exposed to low doses of Roundup® experienced signs of non-alcoholic fatty liver disease (NAFLD).9 The Standard American Diet is laden with glyphosate residues, which might be akin to the ‘chronic low-dose exposure’ utilized in rodent studies. Again, it should be noted that NAFLD is on the rise, with estimates of 25% of Americans having the disease, as estimated by the American Liver Foundation. A 2022 analysis suggested that the overall prevalence of NAFLD worldwide is 32.4%.10 NAFLD can, of course, progress to liver failure in the most serious circumstances.

The Role of Regulation and Risk Assessment

The use of glyphosate has surged over the past several decades due to its effectiveness in controlling weeds, particularly in genetically modified (GM) crops which have been engineered to be glyphosate-resistant. As glyphosate usage increases, so does human and animal exposure. The role of regulation and risk assessment in controlling this exposure is crucial. Yet, the standards and policies that govern glyphosate usage differ widely across the globe.11

Current regulations are primarily based on industry studies and tend to focus on acute, rather than chronic, toxicity. The chronic effects of glyphosate exposure, such as cancer and leaky gut, often take years or even decades to manifest. Thus, the long-term effects of glyphosate exposure are often overlooked in regulatory risk assessments.12 Ethical research practices remain a concern, of course.

Conclusion

As the world’s most widely used herbicide, glyphosate’s potential impacts on human and animal health should not be overlooked. It’s not just about weeds; it’s about our health, our pet’s health, and the health of our planet. A shift towards a more cautious approach, a focus on alternative methods of weed control, and rigorous, independent testing of the long-term effects of glyphosate are essential steps in preserving our health and the environment.

These are complex issues, and they will not be resolved overnight. But with increased awareness and action, we can make a difference. For now, the story of glyphosate continues to unfold, and it’s a story we need to keep telling. You can do your part by not using glyphosate (Roundup®) and other herbicides in your garden and landscaping, as well as supporting efforts to ban glyphosate worldwide.

References

  1. Myers, J.P., Antoniou, M.N., Blumberg, B., Carroll, L., Colborn, T., Everett, L.G., Hansen, M., Landrigan, P.J., Lanphear, B.P., Mesnage, R., Vandenberg, L.N., Vom Saal, F.S., Welshons, W.V., & Benbrook, C M. (2016). Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environmental health: a global access science source, 15, 19.
  2. Drønen, E.K., Namork, E., Dirven, H., & Nygaard, U.C. (2022). Suspected gut barrier disruptors and development of food allergy: Adjuvant effects and early immune responses. Frontiers in allergy, 3, 1029125.
  3. Shehata, A.A., Schrödl, W., Aldin, A.A., Hafez, H.M., & Krüger, M. (2013). The effect of glyphosate on potential pathogens and beneficial members of poultry microbiota in vitro. Current microbiology, 66(4), 350–358.
  4. Puigbò, P., Leino, L.I., Rainio, M.J., Saikkonen, K., Saloniemi, I., & Helander, M. (2022). Does Glyphosate Affect the Human Microbiota? Life (Basel, Switzerland), 12(5), 707.
  5. Zhang, L., Rana, I., Shaffer, R.M., Taioli, E., & Sheppard, L. (2019). Exposure to glyphosate-based herbicides and risk for non-Hodgkin lymphoma: a meta-analysis and supporting evidence. Mutation Research/Reviews in Mutation Research, 781, 186-206.
  6. Zhao, J., Pacenka, S., Wu, J., Richards, B.K., Steenhuis, T., Simpson, K., & Hay, A.G. (2018). Detection of glyphosate residues in companion animal feeds. Environmental pollution (Barking, Essex: 1987), 243(Pt B), 1113–1118.
  7. Székács, A., & Darvas, B. (2012). Forty years with glyphosate. Herbicides-properties, synthesis and control of weeds, 247-284.
  8. Aitbali, Y., Ba-M’hamed, S., Elhidar, N., Nafis, A., Soraa, N., & Bennis, M. (2018). Glyphosate based- herbicide exposure affects gut microbiota, anxiety and depression-like behaviors in mice. Neurotoxicology and teratology, 67, 44–49.
  9. Mesnage, R., Renney, G., Séralini, G.E., Ward, M., & Antoniou, M.N. (2017). Multiomics reveal non-alcoholic fatty liver disease in rats following chronic exposure to an ultra-low dose of Roundup herbicide. Scientific reports, 7, 39328.
  10. Riazi, K., Azhari, H., Charette, J.H., Underwood, F.E., King, J.A., Afshar, E.E., Swain, M.G., Congly, S.E., Kaplan, G.G., & Shaheen, A.A. (2022). The prevalence and incidence of NAFLD worldwide: a systematic review and meta-analysis. The lancet. Gastroenterology & hepatology, 7(9), 851–861.
  11. Benbrook C. M. (2016). Trends in glyphosate herbicide use in the United States and globally. Environmental sciences Europe, 28(1), 3.
  12. Myers, J.P., Antoniou, M.N., Blumberg, B., Carroll, L., Colborn, T., Everett, L.G., Hansen, M., Landrigan, P.J., Lanphear, B.P., Mesnage, R., Vandenberg, L.N., Vom Saal, F.S., Welshons, W.V., & Benbrook, C.M. (2016). Concerns over use of glyphosate-based herbicides and risks associated with exposures: a consensus statement. Environmental health: a global access science source, 15, 19.