Could the herbicide glyphosate be affecting our mental health?

Glyphosate is the most commonly used herbicide in agriculture (e.g., found in Roundup®). Its widespread use is generating significant controversy particularly due to its reported carcinogenic effect. Glyphosate-based herbicides have also been shown to induce neurobehavioural impairments [1]. In an animal study, sub-chronic and chronic exposure to glyphosate increased anxiety and depressive-like behaviours [2].

It is believed that glyphosate may affect health due to its detrimental, lowering effects on beneficial gut bacteria. However, bacteria such as Clostridium spp. and Salmonella strains are resistant to glyphosate [3]. This may result in an overgrowth of these bacteria which at high levels may be neurotoxic. For example, clostridia generate high levels of noxious metabolites which may damage the brain. High levels of clostridia may increase levels of the neurotransmitter dopamine which, at excess levels, can increase free radical activity (oxidative stress) and contribute to mitochondrial dysfunction [4]. Mitochondria are the powerhouses of cells important for energy (ATP) production. In a systematic review, it was reported the Clostridium bacteria are high in children with autism and glyphosate exposure could be a contributory factor [5].

Human exposure to glyphosate is possible through the ingestion of several glyphosate -contaminated foods of agricultural origin. Alarmingly, traces have also been found in formula milk, honey, cereal grains, and soy [6]. In a recent investigation, the presence of glyphosate was found in most beverages for human consumption, derived from agricultural crops, such as beer and wine [7].

While further research is required to clarify the effects of glyphosate (and other environmental pollutants) on human health, it makes sense to do all we can to minimise exposure. This includes eating ‘real’ foods (preferably organic) and increasing the health of our gut by consuming a high plant-based diet. Probiotics may also be helpful for many people.

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References

1. Van Bruggen, A.H.C., et al. 2018. Environmental and health effects of the herbicide glyphosate. Sci. Total Environ. 616–617, 255–268. link to article
2. Aitbali, Y., et al. Glyphosate based- herbicide exposure affects gut microbiota, anxiety and depression-like behaviors in mice. Neurotoxicol Teratol. 2018 May – Jun;67:44-49. link to article
3. Rueda-Ruzafa, L., et al. Gut microbiota and neurological effects of glyphosate. Neurotoxicology. 2019 Aug 20. pii: S0161-813X(19)30081-6. doi: 10.1016/j.neuro.2019.08.006. link to article
4. Shaw, W., 2018. Inhibition of dopamine conversion to norepinephrine by clostridia metabolites appears to be a (the) major cause of autism, schizophrenia, and other neuropsychiatric disorders. link to article
5. Argou-Cardozo, I and Zeidán-Chuliá, F. Clostridium Bacteria and Autism Spectrum Conditions: A Systematic Review and Hypothetical Contribution of Environmental Glyphosate Levels. Med Sci (Basel). 2018 Apr 4;6(2). pii: E29. link to article
6. Rubio, F., Guo, E., Kamp, L., 2014. Survey of Glyphosate Residues in Honey, Corn and Soy Products. J. Environ. Anal. Toxicol. 05, 2161–0525. link to article
7. Cook, K., 2019. Glyphosate in Beer and Wine. link to article