A scientific review identifies glyphosate as a possible cause of the global rise in wheat intolerance. This condition is increasingly reported by people who don’t have a diagnosis of celiac disease (a condition where your immune system attacks your own tissues when you eat the protein gluten), GMWatch reported.

The review authors, Jacqueline A. Barnett and Deanna L. Gibson from the University of British Columbia, note that wheat intolerance has grown in parallel with the spread of the Western diet, which includes high levels of refined carbohydrates. Yet clinical trials have shown that gluten from wheat is not responsible for causing symptoms in healthy individuals, suggesting that something else is inducing symptoms. The authors hypothesise that the “something else” might be glyphosate.

While no GM glyphosate-tolerant wheat is commercially planted in North America, glyphosate-based herbicides are often sprayed on non-GM wheat pre-harvest to desiccate it (“dry it down”).

Glyphosate works as a weedkiller by inhibiting the shikimate pathway, a pathway exclusive to plants and bacteria but not found in mammals, including humans. For this reason, glyphosate was historically claimed to be non-toxic to mammals. But our guts are full of friendly bacteria that help us digest food and function as part of a healthy immune system. Therefore, Barnett and Gibson state, glyphosate could impact gut bacteria, causing “dysbiosis”, an unhealthy imbalance in gut bacterial populations.

Indeed, as they point out, some studies in rats have shown that exposure to Roundup and glyphosate causes dysbiosis, even at relatively low levels that regulators assume are safe to ingest. The dysbiosis effects found include reducing populations of a type of gut bacterium called Rothia. Some Rothia species have been identified as playing a critical role in the degradation of gluten and may play a role in the prevention of celiac disease. The authors state, “These findings suggest that exposure to glyphosate, either alone or in a commercial preparation, at doses previously deemed safe for human health, may have profound effects on microbiome development and may be an environmental trigger in the development of celiac disease.”

After Barnett and Gibson published their review, a 2021 study in rats by Mesnage et al confirmed that the mechanism by which both Roundup and its declared “active” ingredient glyphosate cause dysbiosis is indeed by inhibiting the shikimate pathway in gut bacteria. The gut microbiome was disrupted at all dose levels tested, including those assumed by regulators not to have any adverse effect.

“Friendly” bacteria impacted by glyphosate

In their review, Barnett and Gibson cite research showing that opportunistic pathogens are more resistant to glyphosate compared with the “friendly” bacteria in our gut. Studies reveal that glyphosate and glyphosate-based formulations such as Roundup differ in their effects on gut bacteria. There are also differences in the effects of the different formulations, leading Barnett and Gibson to conclude that herbicide adjuvants (added ingredients beside the declared “active” ingredient) may cause alterations to the gut microbiome and could have synergistic effects when combined with glyphosate.

The authors point out that some of the changes in gut bacterial species found from exposure to glyphosate or glyphosate-based herbicides are linked in other research with certain diseases of the gut, like irritable bowel syndrome, celiac disease, and even colon cancer. Obesity is also known to be triggered by dysbiosis, as are mental health issues. The authors note that exposure to Roundup has been associated with increased anxiety and depression-like behaviours in mice, which correlated with decreases in certain gut bacteria.

The authors state that “Glyphosate may be a critical environmental trigger in the etiology of several disease states, including celiac disease, inflammatory bowel disease and irritable bowel syndrome. Glyphosate exposure may also have consequences for mental health, including anxiety and depression, through alterations in the gut microbiome.”

However, they add that much of the research on glyphosate’s effects on the microbiome suffers from methodological weaknesses such as unrealistically high doses, insufficient duration of exposure, and an over-reliance on animal models, which may not translate well to humans. They conclude that “Future long-term studies examining physiologically relevant doses in both healthy and genetically susceptible populations are warranted to determine the real risk posed to human health.”

The research that anyone can carry out

GMWatch would add that given the ethical impossibility of deliberately dosing humans with herbicides in controlled experiments and the practical impossibility of locking experimental human subjects away and feeding them a glyphosate-free diet over a long-term period, the question of the real risk posed by glyphosate-based herbicides to human health is unlikely to be solved any time soon by scientists working in laboratories.

However – and this may be the true value of this review – anyone suffering from the diseases mentioned by the authors, including the rather generalised but nonetheless real condition of wheat intolerance, doesn’t need to wait for science that may never be done. They can do their own research by minimising their intake of glyphosate-contaminated foods and seeing if they notice improvements. This would entail avoiding GMO ingredients like corn and soy and grains that are habitually desiccated with glyphosate, such as wheat and oats, and favouring organically grown foods.

I’m reminded of a friend who, when I first met him many years ago, confidently informed me that he was “allergic to fruits and veg”. I had come across people who were genuinely allergic to specific foods, but the general nature of his claim alerted me to the possibility that it wasn’t the fruits and veg that produced the reaction – an unnerving rash around his mouth, a burning mouth and throat, and digestive issues – but the pesticides they were grown with. A series of experiments followed in which he ate all the foods he thought he was allergic to, this time grown organically. The result: No unpleasant reactions and the beginning of a healthier diet.