The case so far for Roundup as a contributor to testosterone decline

Jul 2023

Context

There’s a big unanswered question about why men’s testosterone levels are declining. It’s almost certainly multicausal, it just doesn’t correlate closely enough with any single thing we’ve thought to test. A well-established link to obesity is already proven and research into microplastics also suggests a link.

New research suggests another contributor can be found in glyphosate herbicide (Roundup). Awareness is just now beginning to spread, because some of the research suggesting a link was only published in the last year or two. It’s not like there’s a coverup going on here - glyphosate is used because it’s been shown to be safe for human cells at certain levels - but the proposed link takes place through processes in the gut microbiome, and our environmental approvals process mostly doesn’t look into the health of gut microbiota.

Assertions

  1. Men’s testosterone levels have been in decline for decades.
  2. No scientific consensus has been reached for the cause of the decline.
  3. Glyphosate herbicide usage has increased for decades.
  4. Glyphosate works by inhibiting the shikimic acid pathway.
  5. Gut microbes rely on the shikimic acid pathway.
  6. Gut microbes “recycle” testosterone before it’s excreted from the body.
  7. Glyphosate has been found in significant quantities in non-organic foods.
  8. Glyphosate has been shown to alter human gut biome composition.

Hypothesis

Glyphosate reduces free testosterone by inhibiting the ability of Clostridium scindens and similar microbes to use the shikimic acid pathway to produce EPSP synthase, reducing their populations and degrading their ability to process testosterone for reabsorption. So instead of recycling it for reuse in your body, you’re pooping out all your testosterone.

Support for assertions

  1. Men’s testosterone levels have been in decline for decades. You see scare headlines like this all the time, but remarkably, this one turns out to be true. T levels have fallen by something like 20-30% over 40 years. We’ve all been speculating about it for ages: it’s these effete limp-wristed post-industrial jobs! It’s cell phones! It’s tofu! Nah.
    1. Reuters (1997)
    2. Journal of Clinical Endocrinology & Metabolism (2007)
    3. European Urology (2020)
  2. No scientific consensus has been reached for the cause of the decline. Tons of research has gone into causes. Believe you me: if there’s one thing you can trust about capitalism, it’s that we would be marketing a testosterone-boosting remedy to every man in the country. Dudes would be mainlining that shit on the toilet between workouts. Women, now, it’s ok if they all continue taking birth control pills that totally incinerate their endocrine system and screw with their health. But if had definitive proof for what’s screwing with men’s testosterone, it’d be illegal inside of seventy-two hours.
  3. Glyphosate herbicide usage has increased throughout this period. Glyphosate is “Roundup”, a weed-killer produced by Monsanto. Monsanto is the chemicals company so burdened by lawsuits over previous cancer-causing herbicides that it was acquired a few years back by Bayer. Roundup is so popular that Monsanto actually introduced new genes into a lot of our big crops - corn, wheat, etc - and branded them “Roundup Ready”. You can just hose a field down with Roundup, and all the weeds will shrivel and die, but your crops will be resistant. Very handy for the busy modern megafarm harvesting hundreds of tons of food over a few weeks. Again, this isn’t controversial. Glyphosate is well-tested.
    1. Environmental Sciences Europe (2016)
  4. Glyphosate works by inhibiting the shikimic acid pathway. It’s a way to synthesize the main amino acids, the building blocks of cells, from ingredients found in the environment. Roundup is designed to kill a plant by suppressing the expression of the EPSPS gene that allows them to perform this trick. It’s a clever avenue of attack, since human cells don’t have the gene. Just plants … and microbiota.
  5. Gut microbes rely on the shikimic acid pathway. You don’t have millions of microbiota in your gut, or billions. You have trillions of these little microscopic machines! They’re not part of you; they’re not even human cells, they are their own organisms, they just happen to live inside you. You got them from your mom, a lot of them, and from the foods you eat, and all the times you put your fingers in your mouth when you were six. And a majority of them in the human gut have the EPSPS gene, and they use this seven-step pathway to sustain themselves - the pathway that glyphosate works by turning off.
    1. Life (2022)
  6. Gut microbes “recycle” testosterone before it’s excreted from the body. What do your gut microbes do with this magic pathway? They take nutrients from your food, including a lot of the stuff your intestines can’t really absorb, and making stuff out of it. What stuff? A million things, including androgens, like testosterone, that are reabsorbed by your gut and made available to your body.
    1. Journal of Lipid Research (2013)
    2. Molecular Metabolism (2018)
    3. Journal of Complementary and Alternative Medicine (2021)
    4. International Journal of Molecular Sciences (2022)
  7. Glyphosate has been found in significant quantities in non-organic foods. And yeah, this stuff is in your food. In the US we make everything out of industrial corn. which means every Coke, every Gatorate, everything sweetened with high fructose corn syrup has glyphosate in it. Every grain from farms that use Roundup, from a Big Mac bun to a “healthy” whole grain loaf of bread, has glyphosate in it. It’s in your linguine at Olive Garden, your black beans at Chili’s, your sweet potato at Outback, and yes, at Whole Foods too, in your bakery wheat bread and carrots.
    1. Rodale Institute via GMO Free USA (2019)
  8. Glyphosate has been shown to alter human gut biome composition. The defense of Roundup is that it doesn’t get into your body in sufficient quantities to be dangerous to your cells. And with certain exceptions (like the dangerous accumulation of the stuff in groundwater and rivers, from all the agricultural runoff) that’s true. But is it getting into your body in sufficient quantities to be dangerous to those microbiota? You know, the ones that allow you to recycle your testosterone and keep it in your system? Yes! We have research showing how its presence changes the types of gut microbiota that thrive and those that perish.
    1. Life (2022)
    2. Environmental Health Perspectives (2021)
    3. Frontiers in Nutrition (2022)

Conclusion

What does all this add up to? Well, nothing, yet. We haven’t proven anything. But it looks really bad, we’re talking lead pipes bad. I’m cutting all nonorganic foods out my diet, and I’m going to measure my testosterone levels and sample gut microbiota while I do it to see if I can observe any trends in a little supersize-me n=1 experimental trial.

But I’m not a scientist. If you’re interested in this alarming mystery, you should follow people who have made it their career! Stephen Skolnick (https://twitter.com/StephenSkolnick) is a scientist, and writes about a lot of the cutting-edge discoveries being made about the gut microbiome. Jeff Tang (https://twitter.com/tangjeff0) is not a scientist, either, but he’s starting a company dedicated to raising awareness about the testosterone decline and collecting data for research into the problem.