Is Monsanto's Roundup Pesticide Glyphosate Safe

Image Credit: Mike Mozart / Flickr. This image has been modified.

Is Monsanto’s Roundup Pesticide Glyphosate Safe?

GMO soy has been found to be contaminated with pesticide residues (see Are GMOs Safe? The Case of Roundup Ready Soy), but are these levels anything to worry about? I explore this question in my video Is Monsanto’s Roundup Pesticide Glyphosate Safe?.

Researchers out of Norway described the amount of pesticide residues found in GMO soy as high compared to the maximum allowable residue levels. The legal limit for glyphosate in foods had been set at 0.1-0.2 mg/kg; so, these exceed the legal limits by an average of about 2000%, whereas organic and conventional non-GMO soy both had none.

So, what did Monsanto do? Did the industry ditch the whole GMO thing, go back to using fewer pesticides so that residue levels wouldn’t be so high? Or, they could just change the definition of high. What if they could get authorities to raise the maximum residue level from 0.1 or 0.2 up to 20? Then the residue levels won’t look so high anymore. And this is exactly what they did. The acceptance level of glyphosate in food and animal feed has been increased by authorities in countries that use Roundup-Ready GM crops. In Brazil, they went up to ten, and the U.S. and Europe now accept up to 20. In all of these cases, the maximum residue level values appear to have been adjusted, not based on new evidence indicating glyphosate toxicity was less than previously understood, but pragmatically in response to actual observed increases in the content of residues in GMO soybeans—otherwise it wouldn’t be legal to sell the stuff.

What evidence do we have, though, that these kinds of residues are harmful? For 12 years, we’ve heard that Roundup interferes with embryonic development, but that study was about sea urchin embryos. For 14 years, we heard that Roundup may disrupt hormones, but that’s in mouse testicles.

Blogs will dish about concerning new studies implicating Roundup in male fertility, but if we look at the study, it’s about rat testicles. Some blogs cite studies with disturbing titles like “prepubertal exposure alters testosterone levels and testicular shape,” but they’re talking about puberty in rats, though that doesn’t make as catchy a blog title.

Why not use human tissue? Women are having babies every day—why not just experiment on human placentas, which would otherwise just get thrown away? In 2005, researchers did just that. And despite all the negative effects in rodents, glyphosate, the active ingredient in Roundup didn’t seem to have much of a toxic effect on human cells even at high doses, or have much effect on a hormone regulating enzyme, leading Monsanto-funded reviewers to conclude that regardless of what hazards might be alleged based on animal studies, “glyphosate is not anticipated to produce adverse developmental and reproductive effects in humans.”

But pure glyphosate isn’t sprayed on crops, Roundup is, which contains a variety of adjuvants and surfactants meant to help the glyphosate penetrate into tissues. And indeed, when the study was repeated with what’s actually sprayed on GMO crops, there were toxic and hormonal effects even at doses smaller than the 1 or 2% concentration that’s used out on the fields.

Similar results were found for other major pesticides. It took until 2014, but eight out of nine pesticide formulations tested were up to one thousand times more toxic than their so-called active ingredients. So, when we just test the isolated chemicals, we may not get the whole story. Roundup was found to be 100 times more toxic than glyphosate itself. Moreover, Roundup turned out to be among the most toxic pesticides they tested. It’s commonly believed that Roundup is among the safest, though, an idea spread by Monsanto, the manufacturer. However, this inconsistency between scientific fact and industrial claim may be attributed to the huge economic interests involved.

What is glyphosate? Check out: Are GMOs Safe? The Case of BT Corn.

It’s the dose that makes the poison, though. Do we have evidence that the levels of Roundup chemicals not only found on crops, but also in our bodies after eating those crops actually have adverse effects? That’s the subject of the video: GMO Soy and Breast Cancer.

Commercial interests can have a corrupting effect on the science of nutrition and hold sway over institutions that are supposed to operate in the public interest. See for example:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live year-in-review presentations Uprooting the Leading Causes of DeathMore Than an Apple a DayFrom Table to Able, and Food as Medicine


Michael Greger M.D., FACLM

Michael Greger, M.D. FACLM, is a physician, New York Times bestselling author, and internationally recognized professional speaker on a number of important public health issues. Dr. Greger has lectured at the Conference on World Affairs, the National Institutes of Health, and the International Bird Flu Summit, testified before Congress, appeared on The Dr. Oz Show and The Colbert Report, and was invited as an expert witness in defense of Oprah Winfrey at the infamous "meat defamation" trial.

52 responses to “Is Monsanto’s Roundup Pesticide Glyphosate Safe?

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    1. “Roundup is not a pesticide…”

      This is incorrect. An herbicide is a species of which pesticide is the genus. Put another way, the class herbicides is a proper subset of the class pesticides. Similarly, the class insecticides is also a proper subset of the class pesticides.

      1. Art Coses: You taught me something today. I had thought that pesticide meant a substance that kills insects or other living things and that herbicide was a substance that kills plants–mutually exclusive.

        After seeing your post, I checked on Wikipedia (which often enough gets the big picture right) and saw that your explanation of the term pesticide as an umbrella term is accurate. For anyone interested:

        Thanks for the info.

    1. Thanks for your comment Renee.

      In my opinion, the last sentences make it clear “It’s commonly believed that Roundup is among the safest, though, an idea spread by Monsanto, the manufacturer. However, this inconsistency between scientific fact and industrial claim may be attributed to the huge economic interests involved.”

      1. I think you are projecting your own biases. It’s quite a leap to assume that our whole regulatory system has been subverted, without even asking the most simple questions. Like, are there tolerances in foods for presence of inerts used in pesticide formulations ? Please see: US EPA Pesticide Registration website ( . Excerpt from the web page: “Food and Nonfood Use – The only inert ingredients approved for use in pesticide products applied to food are those that have either tolerances or tolerance exemptions in the Code of Federal Regulations (CFR), 40 CFR part 180 (the majority are found in sections 180.910 – 960), or where no residues are found in food. The most up-to-date tolerances and tolerance exemptions are found in the electronic CFR (e-CFR), and InertFinder includes links to the appropriate e-CFR sections.” If you follow the links to the listings of specific inerts , used in pesticide formulations, which are exempted from tolerances, you will see many surfactants. ( So, the in vitro assay (microsomes and cell culture) results reported by this article have doubtful real world significance since the inerts are not detectable in the raw agricultural commodity (mature soybean seed). Perhaps the real exposure risk is to the mixers and applicators of the RoundUp, and especially to those that do not take the required protective measures (gloves, boots, goggles, etc.)

        1. John, your accusation of bias, suggests your own. Your bias is that the government policy is helpful and trustworthy. This means either:
          A. Your research ignores a great body of evidence of government and industry collusion legislative and administrative.
          B. Ignores a great many toxic allowances that have been approved administratively and legislatively only to be rejected as dangerous later on.

          Corporations are allowed to make donations to legislators under the 1st amendment to the U.S. constitution. Corporations are thought to routinely hire bloggers to come in and introduce false arguments to create a point of view in the blogosphere that supports their approach. Which are you-a one sided researcher or a paid blogger?

          1. There is a fine line between healthy scepticism and seeing conspiracies everywhere. Sure big corporations have way too much influence but it is very hard to hide scientific fraud for long.
            I have disagreed with John on GMOs before but your final sentence is absurd. He is no more one-sided than you are and he does his homework. I disagree with some of his conclusions but his arguments are evidence based. Why don’t you rely on evidence that contradicts that presented by John, instead of impugning his motives? That just implies that your case is so weak that you have to get personal.

  1. NO amount of toxic herbicide/pesticides are safe in the long run scheme of things; it is realized as a “foreign enemy” to the body, but once those “enemies” get to be so overwhelming, that’s when the body breaks down and health issues begin. Of course the human body is an amazing machine and can detoxify itself TO A POINT; but there is a cumulative effect of everything we ingest, breathe, apply topically, etc. to our body …. RoundUp/glyphosate is NOT safe in any amount IMO; and I will do everything I can do avoid it.

  2. Roundup/glyphosate kills by interrupting the shikimate pathway of a metabolic function in plants, inhibits creation of essential amino acids. Without the function, plants die. Monsanto insists glyphosate is harmless to human because we don’t have the shikimate pathway. However, bacteria do. The bacteria in our gut have the shikimate pathway.

  3. In 1964, the Stauffer Chemical Co. was awarded patent #3,160,632 for glyphosate – as an ANTIBIOTIC! Down the road, Montsano either took over Stauffer Chemical Co. and/or the patent for glyphosate. Subsequently, Montsano began marketing Roundup as an herbicide w/ glyphosate as the active ingredient. Does the intended purpose differ between an herbicide and an antibiotic? The ends are accomplished: kill biological life. The presence of Roundup in the environment is reflected in sales – in the billions – to homeowners and to commercial enterprises as well as to highway departments of governments. At harvest, wheat is doused with Roundup to dry out the crops in preparation for milling.

    Given that glyphosate has been patented as an antibiotic and dominant in the environment and in foods containing wheat, this chemical kills off a portion of the microbiome of the human gut severely reducing the ability of the gut to digest and absorb nutrients. The body is in a deficit state, compromised.

    1. It is very interesting to see such old data, I mean the patent, which in turn gets even further into the past, mainly with Standard Oil patents and the 2 at that time bio-weapons and weapons manufacturers: Monsanto and Dow’s patents.
      Since glyphosate=N-phosphonomethylGLYCINE has 2 very important functional groups in it structure: glycine (the human inhibiting neurotransmitter!) and phosphate-mimicking site, these 2 facts alone are simply mind-blowing. Glyphosate by mimicking Phosphoenolpyruvic acid, is capable to bind to all the EPSP enzymes and kill every plant out there, except for the GMO’s. This acid, is an important chemical compound in biochemistry, since “it has the highest-energy phosphate bond found in living organisms, and is involved
      in glycolysis and gluconeogenesis”, according to wiki. Thus Glyphosate takes ‘over’ a role of an extremely important natural substance, with the difference, it is ARTIFICIAL, made in labs of weapons manufacturers. In 1932 german scientists KNEW ALREADY how to induce certain cancers which would feed preferentially GLYCINE. Large amount of science was done on the topic ‘glycine and cancer development’ in these OLD DAYS! A science article in May 2012, V.336, p.1040, with the title “Metabolite Profiling Identifies a Key Role for Glycine in Rapid Cancer Cell Proliferation” by Jain et al., only confirms these old findings with newer detection methods. Couple of other articles confirmed the same fact, glycine plays a role in cancer development. Do we need to wonder why glyphosate, mimicking the neurotransmitter, playing role in cancer, came FIRST and GMO’s, resistant to glyphosate, first later?? Maybe one should ask the weapons manufacturers? Dr. Samsel and Seneff, did it, and detected a fraud beyond human imagination, JBPC 2015, v.15, no3, “Glyphosate, pathways to modern diseases IV: cancer and related pathologies”.

      1. Thank you Chris. I remembered a convincing article years ago about the glycine-cancer connection and regretted not saving it.
        There is no doubt about it: this Monsanto glyphosate poison is BAD news.

  4. All company directors of Monsanto should be in a jail for poisoning crops. This massively vile company is an insight into greed, corruption, lies and damned liars. These scum companies are the sick kind of morons producing neonicotinoids, known to destroy pollinating bees ability to carry out their life giving work.
    Monsanto equals the worst kind of scum on the planet.

    1. And TPP will allow multinationals to one up sovereign laws? Corporations now write many laws and will be able legally to overcome national interests.

  5. I thought pesticide was for bugs. Herbicides kill weeds. Actually, Roundup kills any plant that is not GM to be glyphosate resistant.

  6. Does grain fed meat accumulate this poison? Is there evidence people are getting sicker from these poisons? I think eating plants might be safer and healthier.

  7. Dr. Greger doesn’t seem to know how to read abstracts of scientific articles, unfortunately, The study he claims showed nothing to human cells SAYS CLEARLY: “Here we show that glyphosate is toxic to human placental JEG3 cells
    within 18 hr with concentrations lower than those found with
    agricultural use, and this effect increases with concentration and time
    or in the presence of Roundup adjuvants.” Plus this study is from 2005!!! Why doesn’t he cite Seralini’s 2013-2014 study, with rats full of cancers?? Btw. every single drug is tested on RATS first, since once that shows cancers, probability for human cancers is equally high. Glyphosate is an ARTIFICIAL AMINO ACID, acording to Dr. Samsel, which mimicks glycine, the human NEUROTRANSMITTER!! Glyphosate is an antibiotic, metal chelator, and more!! And that should be harmless to us??? What is wrong with MD’s, who can’t even read scientific abstracts?

    1. Clearly you do not know how to read an article since Greger did not write that the study “showed nothing to human cells” (whatever that means).

      And quoting Dr Samsel is simply a bad joke.

      The Seralini study was retracted and its results remain debatable. Citing it would not have been helpful.

      1. If you Google and see sites mentioning the “retraction” of this study by the journal FOOD AND CHEMICAL TOXICOLOGY (where Seralini’s study was originally published), look closely at who is now the Associate Editor of Biotechnology–Richard E. Goodman–a Monsanto scientist for 7 years! Anyone beginning to smell a rat?

        1. Was he the Associate Editor when the article was retracted? Was he the Associate Editor when the article was originally accepted for publication?
          Ascribing all contrary evidence and all inconvenient findings and actions to the machinations of some conspiracy is what the saturated fat crazies do. It is not something that those of us who are unconvinced that GMO foods have been shown to be safe, should do. We would just be dismissed as conspiracy nuts.
          Let’s just rely on the evidence and logic. There is no need to make

  8. Prof. Seralini’s study was republished and the details about it can be found at:

    Regarding Dr. Samsel, read all his and Dr.Seneffs’ articles about glyphosate, instead citing a newspaper written by clueless polarized reporters. Simply go to PubMed and type their names for finding links to their articles..

    Dr. G claims, quote:
    “And despite all the negative effects in rodents, glyphosate, the active ingredient in Roundup ‘didn’t seem to have much of a toxic effect on human cells’* even at high doses, or have much effect on a hormone regulating enzyme,..”
    whereby * relates to an article, cited by Dr. G, and abstract of which I quoted, and, which clearly does NOT compare to the expression ‘didn’t seem to have much of a toxic effects on human cells’..

    I’d suggest to Mr. Goff, if he can, to start reading more often scientific articles, instead of newspapers.

    1. I know what Dr G wrote which is why I objected to the way you wrongly described it.

      The fact is that you misrepresented what was in Dr G’s article either because you did not understand what was written or as a deliberate act to suit some purpose of your own. And you used that as a hook to attack the man for faults which reside solely in your imagination. You still appear to be trying this on. It was, and is, ironic that you criticise others for failings which characterise your posts.

      Seneff is an electrical engineer and Samsel is a consultant of some kind with seemingly little credibility in the wider professional scientific community although a number of his speculations are indeed referenced by PubMed. He certainly appears to be very popular with the crazier end of the blogosphere. Those linked comments on Samsel seem well-founded even if they come from a newspaper article.

      As for the Seralini study, yes I now it has been republished but in a publication which has less strict standards in such matters. And the study remains highly controversial and disputed. It is unsurprising that Dr G did not mention it.

      1. Mr., everyone has an opinion, based on facts and knowledge. And everyone can read, but not understand whats behind. If you want to know more, you need to dig deeper, and start thinking, based certainly not on newspapers, which is a simple JOKE!!!

        1. Limiting one’s research to speculative articles, and assuming that those speculations are established facts, is not helpful. It is always better to look at the evidence as well. Many beautiful theories have been killed by ugly facts.

        1. chris: I do not see anything wrong with Tom’s comments in relationship to your own. As I see it, you have a problem with the content of this NutritionFacts page. Tom Goff disputed your evidence with evidence of this own, directly responding to the credibility of your points. That’s how this forum works. *Civil* discourse is encouraged. If you have nothing new to add, this discussion is probably at a close. – Moderator.

          1. Again I am not understanding the conflict. Dr G is basically saying numbers are manipulated, research is on rat Etc, research is funded by Monsanto and Round Up is toxic. “Most toxic pesticide tested.” Sounds to me like it pollutes our planet.

          2. An article which supposedly exposes Roundup, while basically saying its ACTIVE ingredient, glyphosate is safe (since its was only tested on ‘some animals’) is a joke, equally to the censorship remarks of the moderator!

      2. tom, it seems Dr Seneff had an early interest in biophysics, and her
        suggested revision of prevalent cholesterol theory is both interesting
        and improbable, since it requires joint deficiencies of both
        cholesterol and sulfur. !

        1. Yes, she and Samsel have come up with some interesting and provocative ideas. However, there seem to be people around who think that their hypotheses are absolute truths..

  9. Dr. Greger mentioned a salt water wash based on research in China that removes toxins with a salt water soaking for 20 minutes. Does anyone think it works on roundup? I always wondered how the study showed over 90% reduction in toxic substances in just 20 minutes or so.

  10. If anyone wants to see the effects of the only long-term study (2 years) on GMOs, search French researcher Seralini. Caveat: it’s not for the weak of heart. Massive cancerous tumors formed within 4 months for males and 7 months for females. Monsanto stopped its own “study” at 90 days. Seralini says at that juncture the animals began showing effects on the liver and kidney, but tumors had not yet formed.

  11. Here’s a good one … Check out the YouTube video of a Monsanto lobbyist saying that Roundup was so harmless you could drink it like a glass of water … When offered a glass to prove that, he says “I’m not an idiot.” Priceless.

  12. After roadworks,our local council planted some trees. A couple of weeks later,seeing them being sprayed around the roots and being concerned, I rang and asked what was being sprayed. Ten days later, a gent rang me back saying that Roundup was in the spray. I pointed out that it was considered dangerous. I was told that if used to directions it was perfectly safe and that “there was a lot of misinformation out there about the product” I live on a small sand island ( pop: 20,000 ) connected by a bridge to the Queensland mainland..Australia and just south of the Great Barrier Reef. I see the whole area as being very vulnerable to what is spread or sprayed, but our Council apparently can’t afford to employ a person to hand weed !! Councils here, spray roundup along roadsides and gutters. to stop weeds growing, seemingly without a thought of where the residue ends up.

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