30
Apr
Research Shows Adverse Impacts of Glyphosate on the Human Gut Microbiome
(Beyond Pesticides, April 30, 2021) A bioinformatics tool developed by researchers from the University of Turku in Finland indicates that “54% of species in the core human gut microbiome are sensitive to glyphosate.” This tool may help predict which microbes in the human gut could be negatively affected by exposure to the ubiquitous herbicide. Because damage to the gut biome is linked to a variety of diseases, this information could prove critical in recognition of the role(s) glyphosate may play in the development of human diseases. Published in the Journal of Hazardous Materials, the researchers’ paper states, “The widespread use of glyphosate may have a strong effect on gut microbiomes as well as on human health.” Beyond Pesticides has long reported on the relationship between glyphosate and human health, including potential effects on the human gut microbiome.
Used in multiple herbicide formulations, glyphosate has become widely known as the active ingredient in Bayer/Monsanto’s Roundup®, the most-used herbicide worldwide. The pervasiveness of glyphosate-based herbicide (GBH) use in agriculture, and of Roundup in particular, is due largely to their pairing with genetically engineered (GE) seeds for soy, canola, and corn crops. In many regions, these GE seeds — engineered to resist the glyphosate that is then applied to the crop — dominate.
Farmers have been persuaded by industry that their crop plants will be protected from applications of the herbicide, and that competing weeds will be taken down; for a couple of decades, this more-or-less worked. But more recently, and inevitably, as so much of the agricultural landscape has been drenched in GBHs, weeds are rapidly developing resistance to glyphosate. This has not dampened industry’s enthusiasm for these products; rather, companies are doubling down on chemical solutions.
Very recently, in covering a Tufts University scientific literature analysis, Beyond Pesticides wrote: “Almost five decades of extensive glyphosate use has put animal, human, and environmental health at risk. . . . The chemical’s ubiquity threatens 93% of all U.S. endangered species, with specific alterations [in] microbial gut composition.” In June 2020, we wrote: “Gut microbiota plays a crucial role in lifelong digesti[ve], immune, and central nervous system regulation, as well as other bodily functions. . . . With prolonged exposure to various environmental contaminants [such as glyphosate or other pesticides], critical . . . changes may occur in the gut microbes, influencing adverse health outcomes.”
Glyphosate’s mode of action — the subject of this research — is this: it targets and inactivates an important enzyme in what is called the “shikimate [metabolic] pathway” in plants. That enzyme is EPSPS (5-enolpyruvylshikimate-3-phosphate synthase), which synthesizes three amino acids, phenylalanine, tyrosine, and tryptophan, essential to building proteins. This pathway is not found in animal cells, and so, does not exist as a direct vulnerability to glyphosate in human cells — thus, claims that glyphosate has no health impacts on humans.
There is ample evidence that this industry claim is false, not least among which are:
- the International Agency for Research on Cancer’s (IARC’s) 2015 finding that glyphosate is a probable human carcinogen
- numerous lawsuits against GBH manufacturers for individuals whose exposures led to cancer diagnoses, particularly of non-Hodgkin’s Lymphoma, with some great successes to date
- research that implicates glyphosate in distorting DNA function and links exposures to several chronic diseases (e.g., diabetes, asthma, Alzheimer’s disease, amyotrophic lateral sclerosis (ALS), and Parkinson’s disease)
Impacts of glyphosate on the human gut microbiome represent another pesticide assault on human health. Because the biome harbors between 10 and 100 trillion symbiotic microbes, glyphosate ingestion (via residues on consumed food, primarily) may well have effects on some of those bacteria, according to the subject study. The human gastrointestinal tract and its digestive processes (aka, the “gut”) mediate the function of several systems. Dysfunction of the gut microbiome is associated with a host of diseases, including cardiovascular disease, some cancers, multiple sclerosis, diabetes, asthma, Crohn’s disease, Parkinson’s disease, and inflammatory bowel disease, as well as allergies, autism, depression, obesity, and other disorders or syndromes.
Figuring out what the effects of glyphosate may be is not easy; understanding which microbes in the gut may be vulnerable to glyphosate is a first step that these Finnish researchers have tackled. Their new tool may yield additional evidence that the notion that glyphosate is “safe for humans” is bunk.
The researchers write, “Glyphosate is proclaimed safe for humans and other nontarget organisms because the shikimate metabolic pathway, inactivated by glyphosate, is not present in vertebrates. However, until recently, the presence of the shikimate pathway and diversity of EPSPS in many microbes have largely been ignored. As microbes are ubiquitous, associated with virtually all higher organisms, and essential in maintaining fundamental organismal functions, predicting the consequences of glyphosate use via its potential effects on the microbiome is challenging. The first step toward a more comprehensive understanding of how glyphosate affects higher organisms and biotic interactions involving microbes is to survey microbe susceptibilities to glyphosate.”
The researchers’ bioinformatic method categorizes EPSPS enzymes into four classes, each of which has a different sensitivity to glyphosate, with one of the four classes being particularly vulnerable. The scientists believe that this classification of organisms (by type of EPSPS enzyme) will help evaluate which species are sensitive, or resistant, to glyphosate. The team has already assembled a data set of EPSPS enzymes from thousands of species, including 890 from bacterial species in the human gut microbiome; this is expected to be very helpful in future assessments.
Among the bacteria in the more “vulnerable” categories are: Bacteroides vulgatus, Bifidobacterium adolescentis, Enterococcus faecalis, Staphylococcus aureus, Lactobacillus buchneri, Escherichia [E.] coli, Salmonella typhimurium, Bacteroides fragilis, and Bifidobacterium longum. Researchers expected E. faecalis, L. buchneri, and S. aureus to be resistant to glyphosate’s MO (modus operandi), but found, instead, that they were quite sensitive to it. They theorize that factors other than the EPSPS sensitivity to glyphosate may be at work, potentially including a role for surfactants or other adjuvant or non-active ingredients in GBHs. Beyond Pesticides has written about the unsavory per se and synergistic impacts of so-called “inert” ingredients in glyphosate formulations.
In addition, the co-authors suggest that glyphosate may impact other metabolic pathways (beyond the Shikimate), positing that the mitochondria electron transport chain appears sensitive to the compound. They write, “Even in glyphosate-resistant species, the interference of the herbicide on mitochondrial metabolism may induce oxidative stress and lead to toxic effects.”
Beyond direct effects of glyphosate on the Shikimate pathway in some bacteria, the researchers hypothesize that chronic exposures to the herbicide could lead to the dominance of resistant strains in bacterial communities. They also suggest that some glyphosate-vulnerable bacterial strains could become resistant to glyphosate through “accumulation of mutations in the EPSPS domain or acquisition of a resistance gene via horizontal gene transfer.” Any of these, if found to be valid, could have huge implications for human gut health.
Glyphosate has been the subject of massive controversy, about its safety for humans, non-human organisms, and ecosystems — not to mention the hegemony of Bayer/Monsanto in its control of extraordinarily high percentages of the seed market for corn, soy, and cotton. (As of 2018, more than 90% of these crops in the U.S. were planted with the company’s GE seeds). All those seeds require use of Roundup, of course. Science and environmental advocates have noted the multiple risks the use of glyphosate represents, while industry and big agriculture sometimes minimize or deny those impacts, and even dismiss or distort the science. Those interested might check out Carey Gillam’s talk on Monsanto’s corruption on glyphosate/Roundup at Beyond Pesticides’ 36th National Pesticide Forum.
Beyond Pesticides has reported on EPA’s (U.S. Environmental Protection Agency’s) ongoing failures to protect people and the environment from GBH compounds. One obvious bit of evidence is that the presence of glyphosate in human bodies has risen dramatically during the past three decades. Research out of the University of California San Diego found that, between two data collection periods (1993–1996 and 2014–2016), the percentage of people testing positive for the presence of glyphosate (or its degradates) in their urine rose by 500%, and levels of the compound spiked by 1,208%. With increasing use of GBHs during the past decade, that penetration in human bodies has likely continued to rise. In its Gateway on Pesticide Hazards database, Beyond Pesticides lists glyphosate as having endocrine, reproductive, neurotoxic, hepatic, renal, developmental, and carcinogenic effects on human health.
Beyond Pesticides strongly advocates for a comprehensive policy approach that eliminates not only glyphosate, but all hazardous pesticides registered by EPA, with allowances for limited use of organic-compatible products as a last resort. We also urge communities to work with municipalities, counties, school districts, and other entities to ban the use of glyphosate-based herbicides and all toxic pesticides, and robustly promote the critical transition to organic agriculture and land/turf management. (See this recent win in New York City.)
Beyond Pesticides provides tools, information, and support to take local action: check out our factsheet on glyphosate/Roundup and our report, Monsanto’s Roundup (Glyphosate) Exposed. Contact us for help with local efforts, and stay abreast of developments through our Daily News Blog and our journal, Pesticides and You.
Source: https://www.sciencedirect.com/science/article/pii/S0304389420325462?via%3Dihub
All unattributed positions and opinions in this piece are those of Beyond Pesticides.
