Glyphosate and Human Guts

Peter Ewart

Every year, much of North America and the world is drenched in the weedkiller glyphosate (the key ingredient in Roundup).  Is this safe?  Or are we living in a giant test tube? 

Since 1974, in the U.S., 1.8 million tons have been sprayed on crops, forests, road sides, waterways, golf courses, lawns and school grounds. Worldwide, 9.4 millions tons have been applied (1).  In British Columbia, hundreds of thousands of hectares of forests have been sprayed, with research showing that the residue can linger in some forest plants for up to 12 years (2).

Since the 1990s , when glyphosate was paired with crops that have been genetically modified to be resistant to it, such as GMO corn and soybeans, its use has increased 15-fold.  As a result, glyphosate residue has been detected in 85% of the 10,000 foods tested in the U.S., including corn, honey, breakfast cereal, baby food, crackers, cookies, mushrooms, grapes and green beans (3).

The chemical was first developed as a mineral chelator to clean boilers and pipes, but in 1974 the Monsanto corporation began to promote it as a broad-spectrum herbicide that effectively killed vegetation designated as weeds, yet was supposedly harmless to other forms of life including humans and animals (4).

Glyphosate works by blocking the action of an important enzyme at the cellular level in what is called the ‘shikimate’ pathway which is only present in plants (5)(6). This enzyme is responsible for synthesizing three amino acids which are essential to building proteins.  Without this enzyme, the plant starves to death.  However, vertebrates like humans do not have the shikimate pathway and, as a result, the argument is made by Monsanto that, according to “independent” research, glyphosate does not have a negative impact on human or animal health (Note: some of this supposed research has recently proven to have been “ghost written“ by Monsanto itself) (7).

In any case, Monsanto’s conclusion is disputed by a number of other researchers in the scientific, medical and environmental communities. One of the important reasons they give is that Monsanto is leaving out a crucial component.  And that is the estimated 100 trillion microbes in the human and animal microbiome, which includes the gut and other parts of the body.  Unlike humans and animals, most of these microbes do have a shikimate pathway and thus, as recent research has shown, may be vulnerable to glyphosate (8).

These microbes – bacteria, fungi, viruses and archaea – play a key role in the digestion of food in human and animal guts, as well as regulation of the immune system, and other vital functions.  Without these trillions of microbes inside us, many of which have a symbiotic relationship with our bodies, we would sicken and die. Our knowledge is still limited about the complex interaction between microbes and our bodies.  But we do know that dysfunction of the gut microbiome is associated with a wide range of diseases, including some cancers, cardio-vascular disease, diabetes, Crohn’s disease, allergies, inflammatory bowel disease and other disorders (9).

At the present time, over 96,000 legal cases are pending in the U.S. launched by people who were exposed to glyphosate and have contracted cancers like non-Hodgkins lymphoma and multiple myeloma, as well as other illnesses (10).

Recent research has also shown that glyphosate can have a “perturbing effect” on microbes that live inside insect guts, including bees (11), mosquitoes (12) and beetles (13), as well as on the microbes and fungi that are crucial to the health of the soil itself.  The impact on honey bees is particularly troubling in that glyphosate can significantly reduce “the abundance of beneficial bacterial species that contribute to immune regulation and pathogen resistance” (14).  For their part, bees provide an economically critical role in pollinating crops, as well as supplying honey and other products.

Herb Martin of Stop the Spray BC (15), which is based in the Central Interior of British Columbia, believes that glyphosate spraying could also be affecting the digestive systems of moose with anecdotal reports of moose starving to death yet their bellies remaining full of undigested twigs.  So far, there has not been scientific studies on this topic.  For Martin that is a big part of the problem in that glyphosate is being extensively sprayed on our lands and waters, yet, despite valiant efforts by a few scientists, much has not been researched on its human, animal and environmental effects.  He points out that Monsanto claimed for decades that glyphosate would not persist in the environment beyond 30 days after application.  That claim has since been proven to be absolutely wrong, yet glyphosate continues to be widely used with humans, animals and insects reduced to virtual test subjects.

The glyphosate problem underlines the problem of out-of-control productive forces in North America and the world.  Developments in science and technology can be and are a great boon and benefit to humanity.  But if they are skewed by narrow interests and private profit at the expense of the public interest, difficulties and even disasters arise.  For example, a chemical like glyphosate is not necessarily a bad thing in itself.  In that regard, it is like any powerful or toxic chemical that is discovered.  Such chemicals have to be assessed as to whether they can play a positive or negative role in terms of human health and the environment, rather than as a calculation on the balance sheet of multinational corporations like Monsanto that utilize suspect research to promote their products.   

Currently, the herbicide is out of control in many parts of the world. It needs to be brought under control and that includes banning it completely (such as immediately eliminating all spraying on forest lands) or phasing out its applications on crops and other venues, and adopting safer methods of eliminating weeds.  It also means that more thorough, independent and authoritative research is needed before such chemicals are unleashed on nature and the public.

Peter Ewart is a writer based in Prince George, British Columbia.  He can be reached at:  For some previous articles by the author on this topic go to: and


  1. “Glyphosate fact sheet: Cancer and other health concerns.” USRTK. October 1, 2020.
  2. Botten, L.J. Wood, and J.R. Werner. “Glyphosate remains in forest plant tissues for a decade or more.” Forest Ecology and Management. April 26, 2021.
  3. “Glyphosate fact sheet…” USRTK.
  4. Don Huber. “Disrupting the integrity of Nature – Pesticides and genetic engineering.” Pesticides and you. Volume 37, Number 2, Summer 2017.
  5. University of Turku. “Glyphosate may affect human gut microbiota.” Science Daily. November 20, 2020.
  6. Pesticide Action Network Europe. “Alternative methods in weed management to the use of glyphosate and other herbicides.” 2017.
  7. Carey Gillam. “Whitewash: The story of a weed killer, cancer, and the corruption of science.” Island Press. Washington. 2017
  8. University of Turku. “Glyphosate may affect …”
  9. “Daily News Blog.” Beyond Pesticides. April 30, 2021.
  10. “Glyphosate fact sheet … USRTK.
  11. Erick V.S. Motta and Nancy Morana. “Impact of glyphosate on the honey bee gut microbiota.” NIH. National Library of Medicine. 2020.
  12. “Ingredient in common weed killer impairs insect immune systems, study suggest.” John Hopkins University Bloomberg School of Public Health. May 13, 2021.
  13. Philip Kieffer. “The main ingredient in RoundUp doesn’t just kill plants. It harms beetles, too”.  Popular Science. May 13, 2021.
  14. Erick V.S. Motta and Nancy Morana. “Impact of glyphosate…"

Stop the Spray BC.