WebMD Health News

Roundup Chemical in Your Cereal: What to Know

cinnamon vanilla toasted oats
From the WebMD Archives

Aug. 15, 2018 -- Lab tests of cereals and snack bars made with oats found that many are tainted with the weedkiller glyphosate. Glyphosate is the active ingredient in the widely used herbicide Roundup, which has been linked to cancer.

The tests were commissioned by the nonprofit Environmental Working Group after internal FDA emails surfaced last year showing chemists at the agency were testing wheat, corn, and oat foods for glyphosate and had found “a fair amount in all of them,” but had not yet released those results to the public. The emails were obtained by investigative journalists working for the nonprofit U.S. Right to Know.

Out of 61 food samples tested, 48 had some glyphosate in them. The most heavily contaminated were made with conventionally grown -- as opposed to organically grown -- oats.

The highest level detected, 1,300 parts per billion, was in a sample of Quaker Old Fashioned Oats. The lowest level, 10 parts per billion, came from a sample of Whole Foods conventional rolled oats scooped from a bulk bin.  You can read the full results here.

Oats are the basis of many favorite children’s snacks, including Cheerios and other baby finger-food cereals. Because of their small size and still-developing bodies, babies and young children are more vulnerable to environmental harms than adults are.

Organic products had lower levels of glyphosate; and almost two-thirds of the samples made with organically grown oats didn’t have any detectable glyphosate at all. That’s not too surprising since glyphosate is banned from use in organic farming. Still, some organic products -- 5 samples in total -- did have some glyphosate.

Even organic oats can be contaminated if they sit next to fields where glyphosate is sprayed, or if they’re processed on the same equipment as conventionally grown oats.

What’s the Risk?

So how much should a parent worry about what they’re feeding their kids?

Experts are divided on this point. In 2015, the respected International Agency for Research on Cancer declared that glyphosate was “probably carcinogenic to humans.” There are efforts under way in Europe to ban the chemical. More than 1 million people signed a petition calling on the European Union to prohibit its use, and Germany announced plans to stop its use there by 2021.

Yet in 2017, the EPA said the chemical was “not likely” to cause cancer in people.

“This is where it gets tricky. This isn’t straightforward,” says Michael Davoren, PhD, who studies molecular toxicology at UCLA. He was not involved in the Environmental Working Group’s tests.

Olga Naidenko, PhD, the Environmental Working Group’s senior science advisor for children’s environmental health, says glyphosate shouldn’t be in food, especially the foods we feed to young children.

“We believe that toxic pesticides, especially ones that may be linked to cancer, really don’t belong in the diet,” she says.

But even Naidenko and her co-author, toxicologist Alexis Temkin, PhD, say the odds of getting cancer from eating glyphosate-contaminated oats are really low.

Based on their own calculations, they say a single serving of most of the foods they tested, eaten each day for a lifetime, would cause just one additional case of cancer in every million people.

“That’s such a low increased risk to speculate about,” Davoren says. “When you’re dealing with something like that, a 1-in-a-million increased risk of cancer, I would say that isn’t a significant level to be particularly concerned about.”

He says the risk definitely wouldn’t outweigh the health benefits of eating oats, which are high in fiber and low in fat.

In a statement, Monsanto, a company that makes Roundup and other glyphosate-based products, said “the EWG’s claim about cancer is false. Glyphosate does not cause cancer. Glyphosate has a more than 40-year history of safe use. Over those four decades, researchers have conducted more than 800 scientific studies and reviews that prove glyphosate is safe for use.”

Does that mean glyphosate is safe? You could say the jury is still out on that, but actually, one jury is in back in, and they didn’t think so.

Last week, jurors in California found Monsanto liable for causing cancer in a 46-year-old groundskeeper, Dewayne Johnson. Johnson was awarded $250 million in punitive damages after the jury said the company failed to warn the public about its products’ health risks. Johnson’s case is only the first to come to trial. The company faces thousands of similar challenges across the U.S.

Versatile, Popular Weedkiller

Glyphosate doesn’t merely kill weeds. It also helps get crops ready for harvest. Farmers spray it on oats and other grains so they can move into the field to harvest them sooner. It also helps to promote even drying so they can harvest more of their grain at the same time.

For years, the chemical, which was first used in the U.S. in 1974, was considered to be virtually nontoxic to people and other animals. That’s because it works by blocking an enzyme that’s only made by plants. Since people don’t make the enzyme, the chemical was thought to be basically inert in the body.

But some studies in cells in petri dishes and animals have found that glyphosate and the weedkillers that use it may be able to damage DNA.

Internal company emails presented as evidence in Dewayne Johnson’s trial show Monsanto knew it was “very vulnerable in this area” and that the company hired outside scientists in an effort to discredit this science.

Exactly how the weedkiller might be causing this damage isn’t clear.

Davoren says new studies are pointing to a possible explanation. Though animals don’t contain the enzyme that’s blocked by glyphosate, bacteria do.

In fact, in addition to marketing the chemical as a weedkiller, Monsanto patented glyphosate as an antibiotic in 2010.

Davoren says that because glyphosate is so popular -- it’s the most commonly used weedkiller in the U.S., with more than 250 million pounds used each day -- it’s really hard to avoid.

“We’re learning more and more about the complexity and the importance of the human microbiome,” says Davoren. The microbiome refers to the genes of trillions of bacteria that live in and on our bodies. Our bodies contain about 100 times more bacterial DNA than human DNA. “What’s going on in your microbiome can end up affecting your cancer risk.”

Davoren says the science is still early, but it seems like glyphosate may be most harmful to “good” bacteria -- the kind that dampen inflammation in the body.

“You’re potentially adding one more subtle environmental factor that could tip the scales from a healthy microbiome to an unhealthy microbiome,” he says, though this is still just a theory. Much more research is needed before this can be accepted as fact.

WebMD Health News Reviewed by Hansa D. Bhargava, MD


Michael Davoren, PhD, molecular toxicology program, University of California, Los Angeles.

Olga Naidenko, PhD, senior science advisor for children’s health, the Environmental Working Group, Washington, D.C.

Alexis Temkin, PhD, toxicologist, Environmental Working Group, Washington, D.C.

Environmental Working Group, Children’s Health Initiative: “Breakfast with a Dose of Roundup? Weed Killer in $289 Million Cancer Verdict Found in Oat Cereal and Granola Bars.”

International Agency for Research on Cancer: “IARC Monograph on Glyphosate.”

EPA: “Draft Human Health and Ecological Risk Assessments for Glyphosate.”

U.S. Right to Know, accessed Aug. 15, 2018.


The New York Times: “Germany Aims to End Use of Glyphosate in This Legislative Period: Spokesman.”

The New York Times: “Monsanto Ordered to Pay $289 Million in Roundup Cancer Trial.”

© 2018 WebMD, LLC. All rights reserved.