Should You Worry About Glyphosate (Roundup) in Breast Milk?

For several years, rumors have been circulating online and through society concerning the presence of the weed killer, glyphosate (trade name Roundup) in breastmilk, but that’s all that they are —rumors. In actuality, the issue has been investigated with proper scientific technique and found to be a non-issue. Glyphosate is not present in dangerous, or even borderline dangerous, concentrations in the breast milk of women from a wide range of locations and situations. However, you wouldn’t necessarily know this from searching the topic innocently online, nor especially if you follow social media accounts of anti-GMO activists who have been focusing increasingly on glyphosate over the past few years, because the public has grown tired of hearing about “GMOs” —genetically modified organisms. Consumers are learning gradually that everything alive is genetically modified and that there is nothing inherently dangerous about more modern agricultural genetic technology, compared with older agricultural genetic technology, despite the latter not falling officially into the arbitrary category “GMO”.

As we have discussed hear on The Pulse, so-called GMO foods can be very good for supporting your pregnancy health. You should not fear them. You should embrace them. One particularly good example is AquaBounty salmon. This is the first genetically modified animal to get into the food market, following an approval process that took many, many years. It’s actually a very healthy choice, particularly if you are pregnant, because this salmon, being raised in very controlled environments, grows bigger and faster than any other salmon, so the mercury levels building up per portion of fish should be lower compared with non-GMO salmon. The protein and fats in fish, especially salmon, are extremely healthy for you and your fetus. Mercury contamination in any fish can accumulate in a pregnant woman, causing neurological problems, but also can be devastating to the development of the brain of the fetus — if the mercury exposure is above certain limit. While salmon, regardless of its source, tends to have less mercury contamination compared with certain other fish, such as shark, orange roughy, and swordfish to name a few (do not eat these three fish while pregnant), farmed salmon tends to have less mercury than wild salmon (though it depends on which wild salmon), but AquaBounty genetically engineered salmon should have still less mercury than any other salmon, because it grows so rapidly and to such a large size that there is less time for mercury to accumulate. This makes AquaBounty salmon —“GMO” salmon— a good pregnancy food.

The common misunderstandings about glyphosate and breast milk stem from a couple of bad, very unscientific “studies”.  The more recent such study was published in a scientific journal that is peer reviewed (articles are read by other researchers before they are published), but it is not a high ranking journal and the study was conducted and presented in a fairly anti-scientific way. The other bad study was not even published in a journal and was conducted in the early years of the current century by an activist group, called Moms Across America, who posted its “results” on an internet website. All of the rhetoric that still circulates regarding glyphosate in breastmilk comes from individuals and organizations that still cite these bad studies, while ignoring the actual scientific studies.

Let’s explore this issue, beginning with what glyphosate is and expanding to how it has been studied, good and bad. Developed by Monsanto (a company that later would be purchased by Bayer), glyphosate entered the market in the 1970s. In the 1980s, Monsanto began working on genetically engineering crops to tolerate glyphosate so that it could be used more effectively against weeds, while giving the crops an advantage. This led glyphosate-resistant (“Roundup-ready”) soy to enter the market in 1996 and glyphosate-resistant corn to enter the market in 1998. Many farmers have come to love these and other Roundup crops, such as canola and cotton, because it enables them to produce more food per acre, to engage in less tilling, and to burn less fossil fuel per quantity of food, compared with farmers who cater to the so-called “non-GMO” food industry. This makes the Roundup-ready crops friendlier to the environment compared with crops that are classified as “non-GMO” and “organic”. Specifically, these three factors lower the greenhouse gas contribution of Roundup-ready crops compared with organic and non-GMO crops, but generally farmers like Roundup ready crops and other genetically engineered crops for economic reasons. If a farmer plants Roundup ready corn, for instance, and uses glyphosate as a weed killer, the corn will grow faster and taller than the weeds, and as the corn gets taller, it will shadow out the weeds and inhibit their growth further  even without adding more glyphosate.

Although glyphosate has been classified as what public health experts call a class 2A carcinogen —an agent that probably can cause cancer in humans, the quantities of glyphosate that end up in food made from glyphosate-resistant crops are minuscule and not considered to represent a health risk. Meanwhile, the alternative, naturally-occurring herbicides that the organic farming industry is permitted to use in leu of synthetic herbicides like glyphosate, are themselves toxic. An example of such a naturally-occurring agent that organic farmers use as an herbicide is copper sulfate. This is the blue crystal power that your high school chemistry teacher told you to be very careful not to get on your skin, to wash from your skin if you do get it on there, and avoid getting it near your mouth, because it is very toxic. Yet, the quantities of such naturally-occurring, toxic herbicides that organic farmers can use are not regulated strictly as synthetic herbicides, such as glyphosate, are regulated. Consequently, there is no rationale for one to believe that Roundup-ready crops, and for that matter other genetically engineered crops, pose any health risk compared with organic crops. You can eat Kellogg’s Corn Flakes —whose packaging notes that it is produced with genetic engineering— all day and it’s not unhealthy.

Because they have been largely unsuccessful at convincing consumers that the use of genetic technology in itself makes food dangerous, anti-GMO activists have worked hard over the past several years to equate “GMOs” and biotech agriculture overall with glyphosate. So what is the story with glyphosate and breast milk?

During the early 2000s, Moms Across America purchased some test kits designed to detect glyphosate in water and in some other substances, such as urine. The tests works the same way as a take-home pregnancy test that you can buy in a drug store. It’s called an ELISA test and it works with antibodies. This particular ELISA test for detecting glyphosate was not certified for breast milk and there are many different proteins and other agents in breast milk that can interfere with test results. But Moms Across America is not a scientific organization. It’s an activist group. What it did, supposedly, was to test breast milk from various women with the take-home glyphosate ELISA test kits. The group reported on a website that it obtained positive test results and for almost two decades anti-GMO activists have cited this as a “scientific study” suggesting the presence of glyphosate in breast milk.

More recently, a group of academic-based researchers used the same kind of testing on breast milk and obtained positive results, amazingly obtaining about the same concentration of glyphosate in the breast milk of women from varying environments and social situations (urban, rural, high income, low income, etc). It wasn’t the proper test method and the results sound improbable. They were able to publish in a peer-review journal, but it was an obscure journal, not a high ranking journal. Just to give you an idea of how unscientific it was, in the abstract of the study (a summary appearing at the beginning of a scientific article), the authors wrote that the purpose of the study was to confirm the presence of glyphosate in breast milk.


This is not how science works. Stating that you have set out to confirm the presence of something is actually an anti-science statement. In science, we design the methodology of our studies to try to disprove the hypothesis that is at issue. We try to identify all kinds of situations and factors that can confuse results, causing a false positive, and we design what are called control conditions for this purpose. We do everything that we possibly can to show that the hypothesis is wrong. If we are unable to do that and our methodology is good, only at that point do we propose the results support the conclusion that the hypothesis may be correct. The authors of that breast milk study could not have had things more backwards.

Meanwhile, in recent years, a group of actual breast milk researchers ran a proper study on breast milk, using an appropriate chemical analytic method called Liquid chromatography–mass spectrometry (LC–MS) and guess what. They found no significant levels of glyphosate in breast milk. But given the fear factor —the idea of a carcinogenic substance in breast milk that infants consume— is just too temping for anti-GMO activists to give up. So they still circulate the myth about glyphosate and breast milk. Don’t fall for such pseudoscience. Consume GMO food to your heart’s content. It won’t harm you. It won’t harm your baby. And it is beneficial for the health of the environment on which we and our children depend.

David Warmflash
Dr. David Warmflash is a science communicator and physician with a research background in astrobiology and space medicine. He has completed research fellowships at NASA Johnson Space Center, the University of Pennsylvania, and Brandeis University. Since 2002, he has been collaborating with The Planetary Society on experiments helping us to understand the effects of deep space radiation on life forms, and since 2011 has worked nearly full time in medical writing and science journalism. His focus area includes the emergence of new biotechnologies and their impact on biomedicine, public health, and society.

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