Scientists are calling for a reduction or replacement of agrochemicals as the European Union renews the approval of glyphosate, a herbicide, for another decade. Pesticides have long been associated with Parkinson’s disease (PD) based on evidence from animal models and epidemiological studies. A review article in the Journal of Parkinson’s Disease examines the existing evidence and presents alternative solutions and recommendations.
Professor Daniela Berg, MD, head of the Department of Neurology at Kiel University and University Medical Center Schleswig-Holstein in Germany, emphasizes the need to prioritize human health over other interests, aligning with the third Sustainable Development Goal of the United Nations: Good health and well-being for all.
Experimental evidence suggests that pesticides can directly affect the nervous system, impacting both the central nervous system (resulting in parkinsonism) and the peripheral/enteric nervous system (causing gastrointestinal dysfunction and α-synuclein accumulation).
Furthermore, pesticides may alter the composition and function of the gut microbiota. Dysfunction in the microbiome-gut-brain axis is considered a significant contributor to PD pathogenesis. Many of these changes in animal models resemble gut microbiome alterations observed in PD patients.
The review summarizes the harmful effects of pesticides and highlights an additional health hazard: the detrimental impact of pesticides on the human microbiome.
Diane B. Ré, Ph.D., from the Department of Environmental Health Sciences at the Mailman School of Public Health, Columbia University Medical Center in New York, praises the review, stating that it provides relevant evidence concerning the ongoing debate on pesticide regulations. Ré mentions disturbances in the gut barrier function and the microbiome’s role in propagating pathogenic events from the enteric nervous system to the central nervous system.
Glyphosate, the most widely used herbicide, affects the shikimate pathway found in plants. Although humans lack this pathway, it is crucial for many bacteria. Glyphosate limits the survival of certain bacteria, disrupting the composition of the microbiome and depriving humans of essential products from the shikimate pathway. Kristina Kulcsárová, MD, Ph.D., lead author of the review, explains this phenomenon.
With a projected doubling of PD cases by 2040 and the global surge in neurodegenerative diseases, the undeniable consequences of using glyphosate and other pesticides necessitate further research to understand the mechanisms of toxicity and harmful cascades contributing to the rise of PD. However, there is still reluctance to avoid harmful pesticides.
Feeding the growing global population poses a significant challenge. Prof. Berg acknowledges this but highlights the concern surrounding the rapid increase in neurodegenerative diseases linked to lifestyle and environmental changes, including the use of toxic substances. The association between pesticides and the rising incidence of PD should stimulate research focused on understanding toxicity mechanisms and ultimately eliminating their use.
The goal is to raise awareness among scientists, policymakers, and the general public. While humanity has achieved remarkable advancements, there must be a solution to feed the population without poisoning it.
Moving forward, safety guidelines should incorporate the potential effects of pesticides on gut integrity and the microbiome. Global coordinated efforts are required to establish standardized biomarkers that can identify key changes in the gut and its microbiome associated with PD pathogenesis and progression. This sentiment comes from Hardy J. Rideout, PhD, from the Neurodegenerative Diseases Lab at the Biomedical Research Foundation of the Academy of Athens in Greece, who co-authored the accompanying editorial.
Regulating pesticide use is a complex issue, as the goal of minimizing public health risks must align with concerns about global food supply and insecurity.