Even at “Acceptable” Levels, Glyphosate Disrupts the Bacterial Microbiome (rodent study)

My regular readers know that I have been closely following the growing body of research into the effects of glyphosates on human health.  There has been huge controversy over this for years now.  While humans do not have the shikimate pathway that glyphosate (the active ingredient in the herbicide, Roundup) disrupts, bacteria, fungi and plants do do.  There is growing belief in the scientific community that even low exposures to the chemical disrupts the bacterial microbiome, leading to health issues in the host.

For obvious reasons, today’s study was performed on rats, not humans, and was published in a very eminent journal, Scientific Reports.[i]  The scientists administered Roundup and pure glyphosate in amounts equivalent to what is considered safe for humans (1.75 mg/kg/day)) to dams and their pups.  They then measured urine metabolites.  They found that there was a big difference in metabolites between the moms and their babies, and interestingly, between male and female pups.

Some interesting facts from the paper:

1. “Since glyphosate was first produced in 1974 approximately 9.4 million tons of GBHs [glyphosate-based herbicides] have been sprayed globally, nearly half a pound of glyphosate on every cultivated acre of land.”
2. Prior animal studies have shown that glyphosate alters the microbiome. I’ve covered this topic before:  look here and here. However, very few studies have been done looking at the metabolic effects of glyphosate exposure, especially urinary metabolites, in early life…which is a critical period of both microbiome and brain development.  In fact, “…the animals in this study have been previously investigated for microbiome changes by glyphosate or Roundup exposures, providing initial evidence that exposures to commonly used GBHs, at doses considered safe, are capable of modifying the gut microbiota in early development, particularly before the onset of puberty.”
3. GBH residue has been found in food, drinking-water, crops, animal feed, groundwater, rain and even in air.
4. “Although the effects of GBHs on human health are under intense public debate, evidence is emerging that they impact many health outcomes, including developmental and reproductive toxicity, endocrine disruption, host immunity, obesity and diabetes, gastrointestinal disorders, cardiovascular disorders, and central nervous system dysfunction such as learning and memory impairment, anxiety, depression and autism. These chronic healthy outcomes may occur even at doses lower than established risk safety guidelines, in particular during critical development windows…”

The most startling finding was that in the male pups, there was significantly increased the amino acid homocysteine, which is a huge risk factor for cardiovascular disease and which has been also found at elevated levels in autism.  Actually, homocysteine level is also considered a marker for longevity and inflammatory status in the body.  Further analysis found an inverse correlation between Prevotella and homocysteine:  the lower the Prevotella, the higher the homocysteine level…and vice versa.

The authors point out that “…studies found that children with autism spectrum disorder (ASD) lack microbial diversity and have a decreased abundance in probiotics including Prevotella, potentially leading to reduce folate production by microbiota in individuals with ASD.  As ASD as well as brain damage, cognitive and memory decline have been linked with higher levels of homocysteine, we hypothesize that induced homocysteine by environmental exposure to GBHs during early life may contribute to the development of ASD or other neurodevelopmental disorders.”

The conclusion:  exposure to glyphosate at even currently acceptable levels leads to alterations in the urine metabolome in both rat pups and adults, with male pups being particularly susceptible.

This is really scary stuff.

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[i] Hu J, Lesseur C, Miao Y, Manservisi F, Panzacchi S, Mandrioli D, Belpoggi F, Chen J, Petrick L. Low-dose exposure of glyphosate-based herbicides disrupt the urine metabolome and its interaction with gut microbiota. Sci Rep. 2021 Feb 5;11(1):3265. doi: 10.1038/s41598-021-82552-2. PMID: 33547360; PMCID: PMC7864973.