The Truth About Roundup and Glyphosate – That Every Gardener Should Know

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Robert Pavlis

Several years ago I was going to write a post about Roundup and glyphosate, its active ingredient, but decided against it because several very good science-based reports were produced by others. Unfortunately, those reviews were not directed towards gardeners and based on frequent discussions on social media, the message is still not getting through to the gardening community.

My goal in this post is not to do my usual deep dive into Roundup, but instead I want to give readers a summary overview of the facts along with references containing more details. I hope that putting all of the information in one spot will make it a useful tool for discussions in gardening social media groups.

The Truth About Roundup and Glyphosate That Every Gardener Should Know. photo by Mike Mozart
The Truth About Roundup and Glyphosate That Every Gardener Should Know. photo by Mike Mozart

Roundup vs Glyphosate

Roundup was originally produced by Monsanto and it contained glyphosate as its active ingredient. Most people recognize and use the name Roundup. Unfortunately, Monsanto (now Bayer) has decided that since this brand name is so well known, they could use it to promote other products, some of which don’t even contain glyphosate.

One Roundup product marketed in Europe is vinegar with no glyphosate, and some products contain both glyphosate and another herbicide.

Compost Science for Gardeners by Robert Pavlis

We really should be talking about glyphosate and not Roundup.

Roundup and Monsanto

Conversations that go something like this, “Roundup is toxic because I hate Monsanto” are illogical.

If you hate Monsanto – that is fine. But your love or hate of the company does not change the chemical properties of glyphosate. One has nothing to do with the other.

Does Glyphosate (Roundup) Cause Cancer?

The general public is more convinced than ever that glyphosate (Roundup) causes cancer because of the recent court cases. I’ve discussed this in detail in Roundup (Glyphosate), Cancer and the Courts.

The result of a court case is the sum opinion of the jury, and it does not represent the scientific facts. There is no doubt that the majority of general public hate Monsanto and Roundup, and they truly believe Roundup causes cancer. But that belief does not make it true.

One of the largest agricultural human heath studies has been following workers using glyphosate, for 20 years, and reported, “Overall rates of cancer in the study remain lower than in the general population, especially cancers of the oral cavity, pancreas and lung.”

The science is quite clear on this, there is no evidence that glyphosate causes cancer and most global health and safety organisations agree. The following infographic was prepared by the Genetic Literacy Project, a group promoting truth in science.

The EU Joins the Group

Update: July 26, 2021. I just saw a report from the EU (European Community) that reviewed the science on glyphosate. This 11,000 page report, looking at over 20,000 studies, concluded that glyphosate is safe and does not cause cancer. The only danger they found was that glyphosate “causes serious eye damage”.

Why is this significant? The EU has banned glyphosate in many applications, on a purely political basis, but the average person used this as “evidence” that glyphosate was harmful and caused cancer. It is good to see that the EU scientific community has finally done a proper review. Hopefully, governments will now catch up with the science.

Glyphosate (Roundup) and GMO

A common argument agaisnt GMO plants is that it encourages the use of Roundup. These two issues are unrelated to one another.

Yes, there are some Roundup-ready GMO crops. But the majority of GMO plants have nothing to do with Roundup and they are not Roundup-ready. See GMO Myths – Understand the Truth About GMO Plants for more details.

You can be against Roundup and be for GMO.

Glyphosate (Roundup) Found in Drinking Water and Babies Milk

Studies have found glyphosate in drinking water and in mothers breast milk. The headlines claimed that this was a huge problem, but when you look at the details you realize that it’s a non-issue.

It’s all about the dose.

Our scientific instruments are so good these days that we can find just about any chemical in water and milk. I reviewed the report that found glyphosate in Spain’s drinking water and calculated that you would need to drink the equivalent of 1,000,000,000 bottles of beer, on a daily basis, in order to reach an unsafe level.

The levels found in the environment and in mothers milk are extremely low and of no health concern.

Glyphosate (Roundup) and Chronic Diseases

Some claim that glyphosate causes all kinds of diseases including, diabetes, neuropathies, obesity, asthma, infections, osteoporosis, infertility, birth defects and non-celiac gluten sensitivity. Many of these claims have been made by Samsel and Seneff.

Anyone who has followed the Roundup debate will recognize the name of Dr. Stephanie Seneff. She has made numerous claims about glyphosate which are quickly discounted by the scientific community “as outrageous use of science”. Dr. Seneff is a computer programmer with no experience in chemistry, plant science or health science. Her most recent claim is that glyphosate is a contributing factor of COVID-19.

Unfortunately, the general public eats up her publicity stunts.

A recent review of the claim that glyphosate causes chronic diseases found no support for the claim and went on to say “Our critical analysis of the commentaries published by Samsel and Seneff reveals that their conclusions are not substantiated by experimental evidence but are based on a type of failed logic known as syllogism fallacies. As Nobel Prize-winning theoretical physicist Richard Feynman famously said, “It doesn’t matter how beautiful your theory is, it doesn’t matter how smart you are. If it doesn’t agree with experiment, it’s wrong.””

Glyphosate (Roundup) and Soil Microbes

It is commonly believed that glyphosate harms soil microbes. When glyphosate was added to soil it was found that “it was rapidly degraded by microbes, even at high application rates, without adversely affecting microbial activity.”

Glyphosate (Roundup) and Gut Bacteria

Numerous recent reports in the media and online claim that science has demonstrated glyphosate affects our gut bacteria, and if true could have serious health implications.

One of the reasons glyphosate is so safe is that it only affects a well understood biochemical pathway called shikimate, which is found in plants but not animals. This is the reason it is not toxic to animals. The shikimate pathway is found in some bacteria that live in our gut.

A recent study claims to have shown that glyphosate can affect these bacteria.

Marc Brazeau is the editor of Food and Farm Discussion Lab  and is the Genetic Literacy project’s senior contributing writer. He has done a thorough review of the report claiming a link between glyphosate and gut bacteria and found that the data did not support the conclusions.

The study itself does say, “more studies will be needed to ascertain if there are health implications arising from glyphosate inhibition of the shikimate pathway in the gut microbiome”. The study did not reach any conclusions about glyphosates effect on our health, even though the news reported it with sensational headlines.

Another study found that even levels 50 times larger than the Accepted Daily Intake (ADI) set by European food safety agencies had very limited effect on gut bacteria.

Glyphosate (Roundup) and Bees

A study sprayed honeybees with a normal concentration of glyphosate and found no harm to the bees.

Some studies have looked at bee behavior after exposure to glyphosate, and have reported some learning disabilities in bees.  The number of bees studied was very low, and 1/4 of those were lost during the study. Other studies have looked at exposure to very high levels of glyphosate.

Bees certainly have environmental and pest problems, but glyphosate has not been shown to be one of them.

Facts About Glyphosate

Here are some important facts about glyphosate.

  • our skins absorb very little
  • it undergoes very little metabolism in the body and is mostly excreted
  • it has a very low toxicity; the oral LD50 in rats is 4320 mg/kg, significantly less than vinegar
  • it quickly adsorbs to soil and becomes inactive
  • it has a soil half-life of 50 days, which is short for a pesticide
  • plant uptake from soil is minimal

Not Enough Testing!

The anti-Roundup movement is quick to claim that there has not been enough testing, and that the existing testing was done by labs hired by Monsanto. That is nonsense. Over the last 45 years there have been thousands of studies by labs all around the world.

At some point you have to accept the results.

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Robert Pavlis

I have been gardening my whole life and have a science background. Besides writing and speaking about gardening, I own and operate a 6 acre private garden called Aspen Grove Gardens which now has over 3,000 perennials, grasses, shrubs and trees. Yes--I am a plantaholic!

133 thoughts on “The Truth About Roundup and Glyphosate – That Every Gardener Should Know”

    • 1) I had a look at the article. It tries to say a lot but says almost nothing. A lot of “he said” and “there were plans”. Then they do the usually indirect arguments to convince the casual reader they are right. They did not present any evidence to support their claim. The best they have is “Bayer paid the Genetic Literacy Project $100,000 from July 2020 to June 2021 for its work “to prevent legislative overreach in genetic engineering,” according to the group’s IRS form 990.” That does not mean GLP is a front for the chemical industry. It just means they are a subject expert and got paid for their knowledge. It also means they understand the value of genetic engineering and think the government should stay out of its development. I agree, and I am not a front for the chemical industry. It proves nothing.

      2) Who is USRTK? I had a quick look at their GMO piece. That is a very one sided opinion against GMOs – they clearly don’t want to present the facts. And they go on to link in Roundup – which has nothing to do with the safety of GMOs but it is a common tactic used by groups that have very little science to use to support their opinion.

      Clearly USRTK is a vey biased group – so I put no value in their report.


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