Glyphosate and Human Health: Is the Bacterial Microbiome the Connection?

In various posts, I’ve explored different potential mechanisms that may play a part in the epidemic of biome alterations we have experienced in the industrialized world, including diet, formula feeding, chronic stress, and so forth.  Another potential mechanism, environmental toxins, is another area of interest and something I have been keeping an eye on.

Over the weekend, I got an article[i] that looks at glyphosate (gly) as one possible culprit. This is, of course, a hugely controversial subject but as always, I work hard to maintain scientific objectivity.  It’s all too easy to get caught up in the hype.  But you know me – I want the facts.

I think it would be best to report on this article from conclusion and go backwards from there.  So the conclusion first:  we have no definitive proof at this time that glyphosate is harmful to human health.  There is a paucity of studies, and those that have been done have been useless, in some ways: for example, the amounts used on animals have been far beyond what humans might regularly be exposed to, invalidating their usefulness in truly determining gly’s toxicity to the ordinary person:  “…relating to most studies, the main limitation is the use of high doses of gly…which is difficult to obtain in mammalian tissues, calling into question clinical relevance.”  What we have at this time seems to be a growing body of evidence that there are indirect adverse effects via the chemical’s ability to alter the human bacterial microbiome:  “…the lack of information, contradictory data and independency of studies have generated controversy concerning the safety of Gly for humans….We have assessed the mechanism by which a Gly induced intestinal microbiome disturbance could be involved in emotional disorders and neurological diseases such as ASD [autism spectrum disorders].  However, more research is certainly required to expound the role of Gly on the gut’s bacterial community…”

It is important for you to understand that gly works on plants by disrupting a particular enzyme of the intestine that blocks the formation of certain amino acids.  However, this enzyme is absent in humans and we obtain these amino acids from our diet.  That said, many of the yeast and bacteria, such as exist in the human microbiome, do express this enzyme and thus, are affected directly by gly.

Here are a few of the points they made that really struck me as interesting:

  1. Glyphosate is used in the commercial product Roundup, and studies have shown that it can permeate the water supply and cause changes in animal’s (including mammalian) behavior.
  2. It is found in our food supply: “Traces of the herbicide have recently been found in formula milk, honey, cereal grains or soy…”  It’s also been found in beer and wine.
  3. Toxicity has been demonstrated in other mammals. For example, gly led to infertility and birth deformities in pigs.
  4. There is some correlative data associating the increased use of gly with human diseases including cancer, ADHD, autism, depression, anxiety, Alzheimer’s and Parkinson’s diseases.
  5. Gly is known to damage DNA in rodents as well as in vitro human cell lines.
  6. In mice, chronic ingestion of gly leads to a decrease in the overall number of intestinal bacteria; maternal exposure leads to biome alteration in the pups.
  7. I didn’t have time to get this article to find out who these crazy people are LOL: “…A striking case of voluntary ingestion of gly was reported and indicated a predisposition to the development of Clostridium tertium bacteraemia in humans together with an effect on intestinal mucosa.” People ingested this stuff voluntarily?!
  8. “Few studies have been performed on gly…on microbiota in mammals, but so far, all findings indicate an overgrowth of gly resistant microorganism such as Clostridum spp [species] and possibly several Salmonella Strains…”
  9. “…Gly severely depletes manganese (Mn) levels in plants. Glyphosate’s disruption of the Mn homeostasis selectively affects Lactobacillus and can lead to several disorders such as PD.”
  10. “Evidence of correlations between neurodevelopmental disorders and Gly perinatal exposure were reported in pregnant rodents treated with Gly….” Interestingly, these scientists saw an increase in the release of the neurotransmitter, glutamate, which is similar to what is seen in those with autism.

So to summarize:

  1. Animal studies such as I mention above, and others (including, for example, one which showed that oral exposure to Gly, “…reduces the abundance of Firmicutes, Corynebacerium, Baceroidetes and Lactobacillus…” while also altering mouse behavior) suggest that gly can be detrimental to humans via altering the composition of the bacterial microbiome.
  2. Considering the number of diseases now known to be associated with the depleted biome, and considering how ubiquitous in our diets are sources of exposure (including baby formula which is obviously used very early in life when the biome is developing), this is potentially a huge issue that needs to be actively and diligently researched.
  3. Gly, in the form of Roundup, is “…the most utilized herbicide in agriculture.”
  4. Gly adversely affects probiotic species of bacteria but pathogenic ones, like certain species of Clostridium and Salmonella, are resistant, potentially leading to dysbiosis.
  5. Many more studies must be conducted before conclusions can be drawn.

I’ll continue to monitor this research, of course!


[i] Rueda-Ruzafa, L, Cruz, F, Roman, P, Cardona, D. Gut microbiota and neurological effects of glyphosate. Neurotoxicity. 2019;75:1-8.   doi: 10.1016/j.neuro.2019.08.006

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