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RHR: The Harmful Effects of Glyphosate—and How to Reduce Them


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Glyphosate is the world’s most widely used herbicide and one of the most dangerous toxins that we’re exposed to. About 300 million pounds of glyphosate and [glyphosate-based herbicides] (GBHs) are used in the [United States] annually, with about 90 percent of that on farm fields, and the remaining 10 percent spread between non-agricultural uses like lawns, gardens, golf courses, parks, and, yes, even playgrounds. This episode of Revolution Health Radio is a special Q&A all about glyphosate research. We’ll cover the most recent scientific studies; the harmful effects glyphosate has on human health, from cancer to immune dysfunction, endocrine disruption, oxidative stress, and reproductive harms; and lastly, how to reduce your exposure to glyphosate and mitigate some of the impacts.

Revolution Health Radio podcast, Chris Kresser

In this episode, we discuss:

  • Background on glyphosate
  • Why there is controversy over glyphosate’s toxicity
  • The research behind glyphosate causing cancer
  • Five additional harms of glyphosate
  • How to reduce your exposure to glyphosate

Show notes:

Hey, everybody. Chris Kresser here. Welcome to another episode of Revolution Health Radio. This week, we’re going to do something that I haven’t done for awhile, which is a Q&A episode.

I’ve received a lot of questions over the past several months and even years, really, about glyphosate. And I [wrote] an article about it, back in 2019, on my website. But I realize that I’ve never covered it on my podcast. So I’m going to do that now. Basically consolidating a number of different questions I’ve received about glyphosate into one single episode.

We’ll talk about why glyphosate is one of the most dangerous toxins that we’re exposed to, what the most recent scientific research tells us about glyphosate’s effects on human health, why you probably shouldn’t trust the EPA’s position on glyphosate, and what other less conflicted health agencies have to say about it. [We’ll discuss] the wide range of health impacts that glyphosate has from cancer to endocrine disruption to oxidative stress to immune dysfunction to reproductive harms and, finally, how to reduce your exposure to glyphosate and mitigate some of the impacts.

I’ve come to believe over the years that this is one of the most important health issues of our time along with our exposure to other environmental toxins. But sadly, some of the public health and safety agencies that are supposed to protect us from toxic chemicals have failed miserably. And that’s why we have to take matters into our own hands, and that’s what this podcast is designed to help you do. Let’s dive in.

Background on Glyphosate

Chris Kresser:  So first, a little background. As many of you know, glyphosate is the world’s most widely used herbicide. It’s normally applied in mixtures known as glyphosate-based herbicides (GBHs) and sold under the trade names of Roundup and Ranger Pro. [Genetically modified organism] (GMO) products from Monsanto, which is now owned by Bayer pharmaceutical company, are designed to be grown using GBHs, and the use of glyphosate and GBHs has skyrocketed over the past few decades. In the [United States] alone, usage increased nearly 16-fold from 1990 to 2009. About 300 million pounds of glyphosate and GBHs are used in the [United States] annually, with about 90 percent of that on farm fields, and the remaining 10 percent spread between non-agricultural uses like lawns, gardens, golf courses, parks, and, yes, even playgrounds.

Glyphosate and its metabolites persist in food, water, and dust, often for a very long time after initial treatment. And unlike some other toxins, they’re not destroyed by cooking methods like baking. Given that 13.2 billion pounds of glyphosate have been deployed in the environment in roughly the past 10 years, this suggests that glyphosate has become ubiquitous. And with more GMO crops sprouting up across the globe, glyphosate usage is expected to continue to rise over the coming years. It’s been detected in everything from meat, dairy, [and] fish, to fruits and vegetables, to grains, and even in baby formula. And studies have shown an increase in the proportion of individuals that have detectable glyphosate in their urine over the past several years.

Exposure to glyphosate can be broken down into roughly two categories: occupational, so these are folks who apply or are exposed to GBHs on farms or in parks, or in other environments, and then there’s non-occupational exposure, which occurs mostly through eating contaminated foods, but also through contact with contaminated soil, dust, and by drinking or bathing in contaminated water.

Why There Is Controversy over Glyphosate’s Toxicity

Let’s talk a little bit about the controversy over glyphosate’s toxicity. You might have seen articles in the media suggesting that it’s toxic, and then equally strenuously argued articles suggesting that it’s not toxic. So let’s talk about why that is. First of all, pesticides and herbicides are poisons that are designed to kill things; that’s an incontrovertible fact. So it shouldn’t be surprising that too much exposure to them might be harmful to both animals and humans. And that’s exactly what many studies have found in the case of glyphosate and GBHs. Independent studies, in other words, studies that are not industry funded, have found correlations between glyphosate exposure and increased risk of cancer, kidney failure, fertility problems, birth defects, and much more, as I’ll explain in detail a little bit later in this episode. And independent groups like the International Agency for Research on Cancer (IARC), as well as our own federal agencies, at least some of them, have released reports suggesting that glyphosate is carcinogenic in humans and likely causes many other serious health issues.

On the other hand, we have public agencies like the Environmental Protection Agency in the [United States] (EPA), which have strong ties to industry players like Monsanto and Bayer, who have denied these links between GBHs and health problems, and have claimed that glyphosate is not carcinogenic or harmful at the levels of exposure that humans would typically encounter. They acknowledge, of course, that these products could be carcinogenic or harmful at certain doses, but their argument is that we don’t encounter them in doses that are high enough to cause harm. So a clear pattern has emerged where you have non-industry experts and studies and health agencies like the IARC and the Agency for Toxic Substances and Disease Registry (ATSDR), which is part of the U.S. Department of Health and Human Services, that linked glyphosate with cancer and a bunch of other serious health issues. Whereas regulatory agencies like the EPA are aligning with Monsanto and Bayer and suggesting that glyphosate is safe even after reviewing the same evidence as these other agencies and experts reviewed.

I wish I could say that this was uncommon, but it’s not. Back in 2015, I published an article about how conflicts of interest in scientific research and public health agencies lead to biased reporting, biased interpretation, or both. This is in fact a well-established phenomenon, and it’s been explored in both the media and the scientific literature. Is it really a big surprise that the source of funding of a study could influence its results? After all, as Upton Sinclair famously said, “[It is] difficult to get a man to understand something when his salary [depends upon his] not understanding it.” The time-honored saying, “Don’t bite the hand that feeds you,” also applies here.

Another issue is the revolving door between public agencies like the [Centers for Disease Control and Prevention] (CDC) and [U.S. Food and Drug Administration] (FDA), or institutions like [the] U.S. Congress and pharmaceutical companies. So let me give you a few examples not directly in this field, but in related fields. A year after leaving her position as the director of the CDC in 2009, Dr. Julie Gerberding took a position as president of Merck vaccines. Another former CDC employee, Dr. Thomas Verstraeten, took a position with GlaxoSmithKline while he was still involved in completing a major study on the possible negative side effects of thimerosal, which is a mercury-containing compound used in some vaccines, at the CDC. Over half of lobbyists employed by the pharmaceutical industry in 2008 had worked in Congress or another branch of the federal government and 35 had been former members of Congress. So these conflicts of interest don’t necessarily lead to fraud or misconduct. There are surely many honest and unbiased researchers and physicians that are investigating controversial topics like the impacts of glyphosate or cholesterol targets and statin drugs and genetically modified foods, etc. But we do have evidence of how these conflicts of interest can play out with the glyphosate issue specifically.

Back in 2017, during a lawsuit that was related to glyphosate and human health harms, emails between the EPA Office of Pesticide Programs and Monsanto were released. These revealed that the EPA’s own science program basically concluded that glyphosate was probably carcinogenic to humans, which was in line with the IARC report. But the EPA Office of Pesticide Programs took the position that glyphosate is safe and not carcinogenic. So how could this happen? How could two different departments within the EPA reach separate conclusions about the impact of glyphosate? Well, according to reporting done by the [NRDC], in April 2018, a now retired EPA Office of Pesticide Programs official named Jess Rowland tried to bury a new report by the ATSDR, which suggested that glyphosate was indeed carcinogenic and also caused many other problems. According to an internal Monsanto email that has now been made public, Jess Rowland remarked to Dan Jenkins, a Monsanto employee, “If I can kill this,” referring to the report, “I should get a medal.” And lo and behold, the ATSDR did put their report on the back burner and defer to the EPA’s 2015 assessment that glyphosate was not carcinogenic.

We’re gonna dive into what the independent science really says about glyphosate now. But I wanted to first tell you about this controversy and what’s behind it so you’re not surprised when you see articles claiming that glyphosate is safe, because the EPA [Office of Pesticide Programs] has concluded that it is.

The Research Behind Glyphosate Causing Cancer

I want to talk now about the relationship between glyphosate and cancer. And when we speak about this, we’re speaking specifically about glyphosate’s connection to non-Hodgkin’s lymphoma. That is a broad term for cancers that affect the lymphocytes in the immune system. There are two primary resources or references that examine this relationship that we’re going to talk about here. The first is a meta-analysis by Zhang et al, called “Exposure to Glyphosate-Based Herbicides and Risk for Non-Hodgkin Lymphoma,” published in 2019 and reviews the mutation research. And then a 2018 update to the original ATSDR report that was published back in 2015. So let’s start with the Zhang meta-analysis, which investigated the link between glyphosate and non-Hodgkin’s lymphoma. This meta-analysis looked at six studies, including the most recent update of the Agricultural Health Study cohort published in 2018. And this study was unlike many other previous studies on glyphosate toxicity in three key ways. Number one, the researchers prioritized the highest cumulative exposure based on evidence of glyphosate’s persistence in the environment and because chronic disease, including cancer, is usually the result of cumulative exposure. So they weren’t just looking at one-time exposure; they were looking at exposure over time, and, specifically, they were looking at people who had the highest levels of exposure over time.

Number two, they selected the longest lag or latency between the exposure and the development of cancer. And this is crucial when it comes to cancer, because we know that decades may be needed for the health effects of environmental toxins to manifest as detectable cancers. Generally, it doesn’t work like somebody gets exposed to a carcinogen and then the next year, they develop cancer. That doesn’t happen. It takes many years and often decades for the exposure to manifest in cancer. So, these researchers acknowledged that, and they selected the longer lag or latency to make sure that that was captured in the study. And number three, it’s the only meta-analysis that included the 2018 Agricultural Health Study update. This publication added 11 to 12 more years of follow-up for all the study participants, which is important for the reason that I just mentioned because of the lag time between exposure to a potential carcinogen and the development of cancer. They also add an additional almost 500 cases of non-Hodgkin’s lymphoma, so that increases the sample size. And then they considered five-, 10-, 15-, and 20-year exposure lags, which was not possible back in the original Agricultural Health Study that was done in 2005, because they only followed patients for a short period of time.

Now, the researchers in this analysis found a 41 to 56 percent increase in the risk of non-Hodgkin’s lymphoma in the groups with the highest exposure to glyphosate, depending on the specific cohort they studied. They also documented further support from studies of malignant lymphoma incidents in mice that were treated with pure glyphosate, as well as potential links between glyphosate or GBH exposure and immunosuppression, endocrine disruption and genetic alterations that are commonly associated with non-Hodgkin’s lymphoma or lymphoma genesis. And I’ll come back to some of these other effects a little bit later in the podcast.

Let’s move on now to the ATSDR report, Agency for Toxic Substances and Disease Registry. Sorry for all the acronyms and agencies. It’s really confusing. But I want to make sure we keep it straight. So this was a long-awaited, draft toxicological profile for glyphosate. And it’s an update to their original report that was published several years ago. It’s a pretty hefty tome coming in at almost 260 pages with thousands of references to peer-reviewed literature. And it covered both the cancer and non-cancer health effects linked to glyphosate exposure. I’ll focus on the cancer effects here, and then, as I mentioned, we’ll talk a little bit more about the non-cancer effects shortly. The ATSDR report did a phenomenal job [of] representing the vast and diverse body of scientific evidence linking both pure glyphosate via rodent studies, as well as GBHs in human epidemiologic studies like Roundup, as they are sold on the shelf, to cancer. And I want to bring up an important side note here, which is that many studies suggest that GBHs like Roundup, so [these are] products or mixtures that use glyphosate along with other chemicals, which are really the ones of concern because that’s what humans are typically using. Pure glyphosate is only generally used in animal studies. And these GBH mixtures, like Roundup, are what humans are encountering in the environment. These products are up to 125 times more potent in their effects than the pure glyphosate that’s often used in animal studies. And what this means, of course, is that animal studies that only use pure glyphosate may underestimate the harms of real-world exposure to GBHs like Roundup.

So here are the main takeaways from the ATSDR report. Number one, the higher the exposure and the longer the latency period, again, that’s the lag between exposure and the development of cancer, the higher the association was between glyphosate and non-Hodgkin’s lymphoma. Number two, all three of the meta-analyses that were examined in the report, including one sponsored by Monsanto, showed a statistically significant link with non-Hodgkin’s lymphoma. And number three, almost all studies reviewed in the report showed a strong positive association with cancer, even if they didn’t attain 95 percent statistical significance. And all of them would have likely been significant at a lower 90 percent confidence interval. Statistical significance is important, but it does have limitations in this kind of research. And in fact, according to a petition signed by 800 scientists that was published in the journal Nature, a quote from that, an editorial that accompanied that petition was, “It’s ludicrous to conclude that the statistically non-significant results showed no association when the interval estimate included serious risk increases.”

So what this is essentially suggesting is that just because a study doesn’t achieve that gold standard 95 percent statistical significance, that doesn’t mean we can just dismiss it entirely and conclude that there was no relevant or valid association between glyphosate and non-Hodgkin’s lymphoma. So we have an overwhelming body of evidence now reported in an independent meta-analysis published in a peer-reviewed journal, people who don’t have any industry ties, and then this recent report from the ATSDR, which again, is part of the U.S. Department of Health and Human Services, that are clearly pointing to a relationship between glyphosate exposure and an increased risk of non-Hodgkin’s lymphoma. And we can certainly argue about the exact extent of that risk and some of the finer points, but I think, if you are looking at the independent science on this issue, then it’s pretty difficult to come to any other conclusion that there is an association and the relationship between glyphosate exposure and cancer, non-Hodgkin’s lymphoma.

Glyphosate is the world’s most widely used herbicide and one of the most dangerous toxins that we’re exposed to. This episode of RHR is a special Q&A all about the health impacts of glyphosate and how to reduce your daily exposure. #chriskresser #glyphosate

5 Additional Harms of Glyphosate

But let’s talk about some of the non-cancer harms of glyphosate. These break down roughly into five categories: gut microbiome, [number one]; interfering with the body’s natural detox capacities, number two; disrupting the endocrine systems, number three; causing nutrient deficiencies, number four; and then causing oxidative stress is number five. So let’s start with the gut microbiome. And I’m just going to briefly cover these to give you a general idea. It would take several episodes to do a deep dive into each of these areas. Glyphosate has been shown to disrupt important pathways in our gut bacteria, and this can have a number of downstream effects. It’s also been shown to compromise antibiotics’ ability to fight pathogenic organisms like [Escherichia] coli and Salmonella, and it has been shown to contribute to gut dysbiosis, which in turn has been linked with many other health problems, including obesity, Alzheimer’s disease, autism, [attention-deficit/hyperactivity disorder], type 2 diabetes, etc., etc. I’ve talked about a lot of those other conditions that are linked to disrupted gut microbiome. So I would view this as a fundamental causal mechanism. If glyphosate disrupts the gut microbiome, then we can infer that by extension, it will also increase the risk of all of the conditions that we know are linked to disrupted gut microbiome. Glyphosate also interferes with the body’s natural detox capacity. At high levels, it’s been shown to inhibit key enzymes, including cytochrome P450, in human and rodent cells. And the disruption of cytochrome P450 has been demonstrated in rodent glyphosate feeding studies. So again, those typically use pure glyphosate, and we know that GBHs like Roundup can be over 100 times more potent, so we would assume that a similar impact would occur in human cells.

Cytochrome P450 is a really important enzyme that affects many cellular processes, including detoxification of foreign substances, including medications that people take, cholesterol and vitamin D3 synthesis and degradation, and conversion of testosterone into estrogen to name a few. And that takes us into the third impact, which is endocrine disruption. There’s some research that suggests that glyphosate herbicides act as endocrine disruptors, which interfere with the body’s normal hormone signaling pathways. BPA, or bisphenol A, which is in some plastics, is renowned for this. I’ve talked about that before on previous episodes, but glyphosate has been added to this list. And these endocrine disruptors are insidious because they are known to cause problems over time even at very low levels in contrast to acute toxicity effects, which occur at high levels of exposure. We have cell experiments in vitro that have shown that GBHs interfered with estrogen and androgen receptors, and also with aromatase, which is the enzyme that converts testosterone into estrogen, as I just mentioned.

The next effect is the possibility of causing nutrient deficiency. Glyphosate acts as a chelator. A chelator is something that removes minerals like copper, magnesium, iron, zinc, calcium, etc, from the body or prevents proper absorption and utilization of those minerals in the body. Nearly a third of American adults are already at risk for at least one nutrient deficiency, and when we talk about having optimal levels of nutrients, those numbers are certainly much higher. So glyphosate potentially could contribute to mineral deficiencies, and some studies that have looked at glyphosate’s relationship with chronic kidney disease suggest that mineral deficiency caused by glyphosate may be one of the contributing factors.

Lastly, we have oxidative stress as a mechanism. Oxidative stress occurs when the production of free radicals or reactive oxygen species (ROS) exceeds the body’s ability to neutralize them. It exceeds our body’s antioxidant capacity, you could say. And enough oxidative stress can damage cells, proteins, and DNA, which contributes to the development of cardiovascular disease, autoimmune disease, and pretty much most other chronic diseases. Studies have shown that rodents drinking glyphosate dissolved in water at the highest allowable level for three months had increased lipid peroxidation and glutathione peroxidase, both indicators of oxidative stress. And other in vivo and in vitro studies have also shown that glyphosate induces oxidative stress.

So, as you can see, glyphosate is associated with a wide range of negative health effects, both cancer and non-cancer impacts. And while research on these specific mechanisms is definitely still ongoing, we already have several that have been identified. Glyphosate damages DNA, it disrupts the gut microbiome and endocrine system, it causes oxidative stress, it promotes chronic inflammation, and it contributes to increased susceptibility to pathogens like [Helicobacter] pylori. But perhaps most important, it interferes with immune function by suppressing NRF2 and glutathione, both of which are critical immune molecules that protect against cancer and many other harmful conditions.

How to Reduce Your Exposure to Glyphosate

Let’s finish up by talking a little bit about how to avoid glyphosate and how to protect against the glyphosate exposure that we can’t avoid. Sadly, glyphosate is merely one of the hundreds of environmental toxins that we’re exposed to on a daily basis. And as I mentioned earlier, it’s ubiquitous in the environment and it’s showing up in a greater proportion of individuals’ urine every year. So, unfortunately, I don’t think it’s possible to completely avoid glyphosate exposure at this point in time. That said, there are several things you can do to reduce your exposure. The most important step is to eat organic food. Certified organic foods are free of toxic herbicides like glyphosate. They have lower pesticide residues and are richer in micronutrients. And studies have shown that glyphosate urine levels were lower in people who chose mostly organic food versus those who ate conventional foods. At the risk of stating the obvious, not using Roundup or other GBHs in your garden, or in any other environments that you would encounter, if you have a farm, or if you spend time in a certain outdoor environment that has a weed problem, not using those products is a really good first step. You might want to check with your kids’ school to see if they’re using those products. And if they are, you can [try to] get them to stop, and you can refer them to this podcast or blog article, as well as the ATSDR report.

We’ll put links to all that in the show notes. Because I think it’s impossible to entirely avoid glyphosate exposure and because of the significant health harms that are associated with it, I think it makes sense to take steps to mitigate the impact of exposure. And this includes doing all of the things I previously talked about to improve our innate detox capacity, including eating a nutrient-dense anti-inflammatory diet, exercising regularly, getting enough sleep, managing stress, reducing exposure to other environmental toxins that could further compromise our detox capacity, and this could include things like avoiding plastics that contain harmful chemicals like BPA and plasticizers, switching your cosmetics and personal care products to greener, more natural varieties, installing a water filter and home air purifier, and cleaning your home with less harsh or more natural products. There are some supplements that improve glutathione and NRF2 status. I mentioned that the depletion of glutathione and interfering with NRF2 are two of the biggest, most harmful mechanisms of glyphosate exposure.

So things that we can do, [foods we can] eat, and supplements we could take to improve glutathione and NRF2 status could make a lot of sense here. And I have done and I’m in the process of doing a very deep dive on researching the various molecules that might be helpful in mitigating glyphosate harms. I will come back to you with a specific recommendation there. Because I think it’s really critical to apply the precautionary principle here, that we’re exposed unwittingly and unwillingly often to these toxins, they’re impacting our health, and, unfortunately, we simply can’t avoid them in some cases. So we want to take steps to make sure that we’re mitigating the impact of that exposure.

I’ll do this on a future episode because this one is already getting a little bit long, especially for a solo episode where you just listen to me talk the whole time. So look out for another episode in a couple of weeks where I will address this and make specific recommendations. And also, make sure you’re on my email list to get updates about this. You can go to ChrisKresser.com and sign up for that. And thanks for listening. Thanks for being a listener and for sending in your questions. I know we haven’t been doing a lot of Q&A episodes recently, but I do read them and it helps direct some of the topics for guests that I invite. And as I mentioned in a recent podcast, it’s the 11-year anniversary of my show, and I’m starting to think again, about how to make it better. And one of the things that we get a lot of requests for is more Q&A and solo episodes on topics like this where we can do a deep dive. So I will probably be doing a few more of these in the future.

Okay, that’s it for today. Keep sending your questions in to ChrisKresser.com/podcastquestion, and look out for an episode in a few weeks where I talk a little bit more about specific molecules or supplements that I think could be helpful here in addition to dietary suggestions. Take care everybody; talk to you soon.

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