A new study reveals a hitherto unknown mechanism behind how the world’s most popular GMO herbicide harms the brain.
Remarkably, despite Roundup® herbicide’s widespread approval around the world, the most basic mechanisms through which it exerts toxicity towards non-target animal species (including humans) have yet to be adequately characterized.
Concerned about Brazil’s status as the largest global consumer of pesticides since 2008, researchers sought to elucidate toxicologic effects of these agrochemicals in humans.
Their new study, published in the journal Toxicology, provides a proposed mechanism for the adverse neurological effects of Roundup® (a glyphosate-based herbicide). It is has been observed that agrochemical exposure can lead to, or accelerate, neurodegenerative disorders, such as Parkinson’s and Alzheimer’s disease. However, lacking a mechanism of action, such a link can more easily be written off as coincidental; which is largely the position of the medical establishment, agricultural industry, and its would-be regulators. The authors point out that, “neurodegenerative conditions are frequently associated with glutamatergic excitotoxicity and oxidative stress,” which is why they decided to investigate the subject further.
Titled, “Mechanisms underlying the neurotoxicity induced by glyphosate-based herbicide in immature rat hippocampus: Involvement of glutamate excitotoxicity,”[i] the paper tested the neurotoxicity of Roundup® in the hippocampus of immature rats following acute exposure (30 minutes) and chronic (pregnancy and lactation) exposure.
The results found that acute exposure to Roundup® induces calcium influx into neurons (primarily, by activating NMDA receptors and voltage-dependent Ca2+ channels), leading to oxidative stress and neural cell death. They also found that the herbicide affected the enzymes ERK and CaMKII, the later of which is an enzyme whose dysregulation has been linked to Alzheimer’s disease.[ii] Additionally, acute exposure was observed to have the following three effects:
- Increase the amino acid glutamate into the junctions through which neurons communicate (synaptic cleft), which, when released in excess levels, can exert excitotoxic/neurotixc effects in neurons.
- Decrease the neuroprotective antioxidant glutathione.
- Increase ‘brain rancidity,’ i.e. lipoperoxidation, characterized by excitotoxicity (over-stimulation of the neurons) and oxidative damage.
The summation of their results, looking at the effects of both acute and chronic exposure, were reported as follows:
Taken together, these results demonstrated that Roundup® might lead to excessive extracellular glutamate levels and consequently to glutamate excitotoxicity and oxidative stress in rat hippocampus.
Roundup-induced glutamate excitotoxicity appears to share similar effects to monosodium glutamate (MSG) and aspartame-linked excitotoxicity, and indicating that anyone either prone to, or suffering from, a brain or neurological condition involving increased oxidative stress and/or neuronal excitotoxicity (pathological or excessive nerve cell stimulation) should be even more wary to reduce exposure to this unfortunately ubiquitous environmental and food contaminant.
The authors also pointed out that their study found maternal exposure to Roundup® resulted in the offspring being exposed to the herbicide because it crosses the placental barrier during gestation and/or it is passed to them through the breast milk. They caution:
Exposure to environmental toxicants during pregnancy and suckling periods has the potential to affect embryo and fetal development.
For additional information on the adverse effects of Roundup herbicide and related glyphosate formulations, visit our database sections on the topic, which references peer-reviewed and published research from the National Library of Medicine on the chemical.
[i] Daiane Cattani, Vera Lúcia de Liz Oliveira Cavalli, Carla Elise Heinz Rieg, Juliana Tonietto Domingues, Tharine Dal-Cim, Carla Inês Tasca, Fátima Regina Mena Barreto Silva, Ariane Zamoner. MECHANISMS UNDERLYING THE NEUROTOXICITY INDUCED BY GLYPHOSATE-BASED HERBICIDE IN IMMATURE RAT HIPPOCAMPUS: INVOLVEMENT OF GLUTAMATE EXCITOTOXICITY.Toxicology. 2014 Mar 14. Epub 2014 Mar 14. PMID: 24636977
[ii] Yamauchi, Takashi (August 2005). “Neuronal Ca2+/calmodulin-dependent protein kinase II—discovery, progress in a quarter of a century, and perspective: implication for learning and memory”.Biological & Pharmaceutical Bulletin 28 (8): 1342–54. doi:10.1248/bpb.28.1342. PMID 16079472.
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