Study increases urgency for organic transition
The study featured in the article below is co-authored by Drs Robin Mesnage and Michael Antoniou.
Environmental pesticide exposure alters gut microbes, increasing urgency for organic transition
Beyond Pesticides, 12 May 2022
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A report published in Environmental Health finds that exposure to environmentally relevant concentrations of pesticides can alter gut microbial communities, as demonstrated through fecal samples. Over 300 environmental contaminants and their byproducts, including pesticides, are chemicals commonly present in human blood and urine samples. Ample evidence demonstrates that environmental contaminants, including pesticides, negatively affect the human mouth and gut microbes. However, fecal samples provide an accurate representation of the microbial community existing in the gut. These toxicants can alter hormone metabolism, which adversely affects health outcomes. Adverse health effects of environmental contaminants include reproductive and developmental defects, diabetes, cardiovascular disease, liver disease, obesity, thyroid disorders, and improper immune operation.
Although studies show how chemical exposures affect human health, more research is now questioning how these toxic chemicals influence gut health. Therefore, studies like these highlight the importance of evaluating how chemical contaminants deregulate normal bodily function through microbiome changes. The report notes, “Our results highlight the need for future dietary intervention studies to understand effects of pesticide exposure on the gut microbiome and possible health consequences.”
Researchers examined dietary exposure to 186 common pesticide residues in the fecal excrement to determine impacts on the microbiome among 65 twins in the United Kingdom. Gut microbiota composition has associations with dietary habits, different life stages, geographical location, exercise, antibiotics, and disease states. However, researchers investigated if these associations can also impact concentrations of pesticide residues in excrement to indicate gut health alterations. Using metagenomics and metabolomics, researchers measured the metabolic activity of microbes in fecal matter and pesticides in urine excretion to note any bodily changes.
The report finds all urine samples contain pyrethroid or organophosphate insecticide residues, with 53 percent of urine samples containing glyphosate. Individuals who consume more fruits and vegetables grown with chemical-intensive practices have higher concentrations of organophosphate residues. Although urinary metabolite (pesticide breakdown product) excretion lacks a correlation with gut microbial changes, there are 34 associations between the concentration of pesticide residues and metabolite residues in fecal matter and gut health. Glyphosate excretion in the fecal matter correlates with an increase in bacterial species richness, fatty acid metabolites, and phosphate concentrations in the gut. For pyrethroids, deltamethrin metabolite, Br2CA, has a positive association with phytoestrogens enterodiol (dietary estrogen) and negative associations with specific amino acids in the gut.
The gut microbiome is a group of microorganisms, including bacteria, archaea, viruses, and fungi, that plays a crucial role in digestion, bodily function, detoxification, and immune and central nervous system regulation. Through the gut biome, pesticide exposure can enhance or exacerbate the adverse effects of additional environmental toxicants on the body. Since the gut microbiome shapes metabolism, it can mediate some toxic effects of environmental chemicals. However, with prolonged exposure to various environmental contaminants, critical chemical-induced changes may occur in the gut microbes, influencing adverse health outcomes. Like gut microbes, soil microbes are essential for the functionality of the soil ecosystem. Toxic chemicals damage the soil microbiota by decreasing and altering microbial biomass and soil microbiome composition (diversity). Pesticide use contaminates soil and results in a bacteria-dominant ecosystem causing “vacant ecological niches, so organisms that were rare become abundant and vice versa.” The bacteria outcompete beneficial fungi, which improves soil productivity and increases carbon sequestration capacity. The resulting soil ecosystem is unhealthy and imbalanced, with a reduction in the natural cycling of nutrients and resilience. Thus, plants grown in such conditions are more vulnerable to parasites and pathogens. Moreover, the effects of climate change only exacerbate threats to soil health as studies show a link between global climate change and a high loss of microbial organisms in the soil ecosystem.
The findings add to the growing quantity of environmental studies linking pesticide exposure to metabolic distress and the respective health consequences. Although previous studies suggest pesticide exposure in the environment disrupts the gut microbiome, this report is the first to find an association between pesticide excretion and exposure to environmentally relevant concentrations of pesticides. Although most pesticide exposure decreases microbial species richness, some chemicals, like glyphosate, increase bacterial species richness. However, an increase in species richness is not always positive as it cannot measure the function of how these bacteria work together. Studies find functional diversity declines faster with agricultural intensification than species richness. Functional diversity involves the interaction of species based on similarity in behavioural, morphological, physiological, or resource use as it relates more strongly to ecosystem function.
Moreover, an increase in species richness in the gut microbiome can allow more resilient bacteria to flourish and outcompete other beneficial bacteria regardless of pathogenic potential. For instance, glyphosate kills bacterial species beneficial to humans and incorporated in probiotics yet allows harmful bacteria to persist, leading to resistance. Similarly, glyphosate-exposed soils contain a greater abundance of genes associated with antibiotic resistance and a higher number of inter-species transferable genetic material. Antibiotic resistance can trigger longer-lasting infections, higher medical expenses, the need for more expensive or hazardous medications, and the inability to treat life-threatening illnesses. Nevertheless, studies show an organic diet lowers individual exposure to pesticides, demonstrating a significant reduction in bodily pesticide concentration. Therefore, organic can also protect human gut microbe health by reducing the number of toxic chemicals within the body.
The report concludes, “We found that individuals who are regularly consuming organic products had higher healthy eating index values, but that other lifestyle choices are, in all likelihood, also contributing factors. We provide the first evidence of an association between pesticide excretion and changes in gut microbiome metabolism at environmental levels of exposure in the UK population. Our findings highlight the need for future dietary interventional studies to understand the impact of pesticide exposure on gut microbiome composition and function and its health implications.”
To improve and sustain microbial communities, and thus human, animal, and environmental health, toxic pesticide use must stop. Beyond Pesticides challenges the registration of toxic chemicals due to their impacts on soil, air, water, and our health. While legal battles press on, the agricultural system should eliminate the use of toxic synthetic herbicides to avoid the myriad of problems they cause. Instead, Beyond Pesticides holds that safer alternatives are available, and organic practices can protect public health and the environment. In addition to positive impacts on the human microbiome, organically grown food (i.e., milk, meat, strawberries, tomatoes, and a range of other foods) contain a much more diverse bacterial community than their conventional counterparts.
Moreover, purchasing organic food when possible can help curb exposure and resulting adverse health effects. Emphasis on converting to regenerative-organic systems and using least-toxic pest control to mitigate harmful exposure to pesticides should be the main focus. Learn more about soil and gut microbiota and its importance via Beyond Pesticide’s journal Pesticides and You. Additionally, learn more about how pesticides affect human health by visiting Beyond Pesticides’ Pesticide-Induced Diseases Database, which supports the clear need for strategic action to shift from pesticide dependency.
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
Source: Environmental Health