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Estrogenic Chemicals in Meat

We’ve known since 1939 that there were “cancer-producing substances” in roasted meat. Scientists have since identified these compounds as heterocyclic amines, described by the National Cancer Institute as “chemicals formed when muscle meat, including beef, pork, fish, and poultry, is cooked using high-temperature methods, such as pan frying or grilling….”

As I describe in my 2-min. video Carcinogens in Roasted Chicken, studies on rodents have historically downplayed the risk, suggesting 99% of these chemicals can be removed by the liver. Humans, it turns out, are 50 times less able to detoxify these carcinogens, though. This may explain why studies done on Long Island and around the world have shown women eating more broiled, grilled, fried, barbequed, and smoked meats appear to have up to five times the risk of developing breast cancer (see also Muscle Tremors & Diet and Fast Food Tested for Carcinogens).

More than 85% of breast cancers are sporadic and attributable to long-term exposure to environmental carcinogens, such as those in the diet, through a multistep disease process progressing from non-cancerous to premalignant and malignant stages. Most cancer-causing agents are involved in either the initiation stage of cancer, triggering the initial DNA mutation (like radiation), or the promotion stage of cancer, promoting the growth of the tumor (certain hormones like IGF-1). But heterocyclic amines in cooked meat like PhIP are considered “three strikes” carcinogens because they are not only DNA-damaging mutagens and promote cancer growth, but also increase its metastatic potential by increasing tumor invasiveness.

Strike 1: By asking women undergoing breast reduction surgery about their meat cooking methods, researchers were able to directly correlate the number of DNA mutations found in breast tissue with the estimated dietary intake of these cooked meat carcinogens.

Strike 2: In my 4-min. video Estrogenic Cooked Meat Carcinogens I show that not only may these meat chemicals trigger the original cancer-causing mutation, they may also then promote the growth of the tumor. PhIP for example activates estrogen receptors on human breast cancer cells almost as powerfully as pure estrogen. Even at very low doses, the cooked meat chemical PhIP appears to drive the growth of breast cancer.

Strike 3: Check out my 3-min video PhIP: The Three Strikes Breast Carcinogen to see what affect these cooked meat carcinogens may have on the invasiveness and metastatic potential of human breast cancer. The growth hormone IGF-1 may also promote tumor progression and invasion (see IGF-1 as One-Stop Cancer Shop). IGF-1 is released by our liver in response to animal protein consumption regardless of how it’s cooked (why? See Higher Quality May Mean Higher Risk.) On the other hand, broccoli and Indian gooseberries may have both anti-proliferative and anti-invasive properties: Lung Cancer Metastases and Broccoli and Amla Versus Cancer Cell Invasion.

Most of the experiments on the cancer-causing effects of cooked meat chemicals were done on breast cells in a petri dish, though. How do we know these carcinogens make it not only into the breast after you eat cooked meat, but into the breast ducts where most breast cancers arise—so-called ductal carcinoma.  Researchers didn’t know for sure, until a study out of Canada measured the levels of PhIP in the breast milk formed in those ducts of nonsmoking women. The average concentration of the “three strikes carcinogen” found in the breast milk of meat-eating women corresponded to significant cancer growth activation. One of the women was vegetarian, though, and none was detected in her breast milk.

-Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my videos for free by clicking here and watch my full 2012 – 2015 presentations Uprooting the Leading Causes of Death, More than an Apple a Day, From Table to Able, and Food as Medicine.

Adapted from Kathy Freston’s excellent post Anti-Breast Cancer: The ‘Three Strikes’ Carcinogen to Avoid 


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.

11 responses to “Estrogenic Chemicals in Meat

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  1. Dr. Greger, this is a really generalized question, but do you have any overall theory or idea of why animal products are so harmful and plants the opposite? The animal part isn’t too difficult. I can think of plenty of plausible reasons for animal consumption to be unhealthy. But what about the opposite? Why are so many plants health promoting? If it was just the absence of harm from animal products that would be easy to understand, but I have trouble coming up with a plausible evolutionary reason for so many plants being health promoting and disease fighting.

    1. I think this is a matter of context.

      We live in an era of overly hyped plant “superfoods”. No disrespect to Dr. Greger, I love the profiles on amazing plant foods he provides, but I think he does a good job of rounding out the subject to basically show that ALL plant foods are superfoods. And I love the caveat he routinely adds that “the best vegetable/fruit is the one you eat”. The same can’t be said for the general media, who tend to fixate on goji and acai berries and the like and ignore all the boring foods like apples, pears, romaine lettuce, carrots, tomatoes, etc who are super in their own right but not nearly as exotic or sexy.

      We live in a place and era where to not die of a heart attack or cancer means you must be in a state of exceptional health!

      Let’s take a step back. What if our diet is supposed to be made up entirely of these superfoods? And having excellent health is just the normal and expected result of that. It shouldn’t be considered extraordinary to be in good health. It shouldn’t be considered extraordinary to not succumb to completely avoidable diseases and to have a long healthy life as a result of eating the foods we’re physiologically designed to.

      A lion doesn’t get atherosclerosis from the meat it eats; it doesn’t promote carcinogen formation by cooking its meat; it has a shorter digestive tract so even the carcinogenic substances present in the raw meat are ushered out of its system faster. And its life span is so much shorter than ours that cancer cell proliferation is perhaps not so much of an issue compared to humans or other long-lived herbivores. It eats meat, as it’s physiologically designed to, and enjoys better health than if it were to eat grass. A diet of leafy greens, mushrooms, and berries would certainly not be health promoting for the lion. It’s just a matter of eating the right diet for whatever type of animal you are.

      Honestly the ‘evolutionary reason” seems so clear to me that I can’t even put it into words. Basically, I think excellent health should be the baseline for what we consider normal health. Unfortunately we have a confused relationship between what is “average” and what is “normal”.

      1. Definitely a lot of the benefit of plants seems to be that you’re simply eating less animals. Then again, I guess there are plenty of poisonous plants… so perhaps we’ve just learned to cultivate the good ones. But then we’ve learned to cultivate animals too and they’re not good at all. It just seems rather convenient that there aren’t more unexpected side effects to plant food consumption.

        1. There is. If you eat the wrong plants… are allergic or generally eat badly. There is lot of evidence that shows humans grow up more like primates eating high amounts of greens, a lot like gorillas. So the reason plants are so good for us… is well because we have got very good at absorbing thr nutrients in them. When there isn’t much around but leaves so you eat them like crazy… you kind of get good at digesting and abosrbing nutrients from them. In other words it’s because we have evolved primaraly on a plant based diet… and it is a modern thing to eat high amounts of meat or fish and animal products in general. What I mean is. Humans would have eat a high plant based diet in the tropical regains originally. Even in winter areas we learned to cultivate starch based foods as they lasted well through the winter. And generally animals took time to grow feed get them to mate… and so people in general eat a lot less meat. So it’s simple a case in my opinion that we haven’t evolved enough to be able to deal with meats and animal products. And to be honest I hope we never do. It’s a bad idea to become dependent on animals, they’re very unpredictable.

    2. Dave T – Simply put, plants produce chemicals to protect them from external threats. They produce antioxidants to protect their cells from sunlight damage, and nasty tastes / poisons to protect from being eaten. We have adapted to learn which to eat and which not to eat, as we face many of the same challenges – eg oxidation damage from sunlight.

    3. The main reason is that we are not carnivores – for 60 million years our primate ancestors have been largely fruit, leaf and occasional insect eaters, while animals have only been a substantial fraction of the diet for about 2 million. Most of the health damaging effects of high animal product diets occur after our fertile years, so we haven’t experienced enough selective pressures to adapt. True carnivores don’t suffer cardiovascular disease.

      Another big part of it is that animal chemistry is so similar to our own. Their hormones are often identical, their proteins are similar enough to provoke immune responses against our own proteins, and their high levels of saturated fats and methionine heavy protein are superfluous to our needs.

      Meanwhile plants, unable to flee or find shade, have used chemical defenses against sunlight and predation for 500 million years. We animals evolved to neutralize some of the insecticidal toxins plants produce, which in food sized doses stimulate our own cellular detoxification apparatus. Indeed, in their absence (as on an animal product heavy or highly processed diet), perhaps our cells aren’t getting the chemical cues to mount a defense against stressors that they used to.

      While the title may seem tangental, I thought this was a pretty insightful article that touches on your question:

      Mattson, Mark P., and Aiwu Cheng. “Neurohormetic phytochemicals: Low-dose toxins that induce adaptive neuronal stress responses.” Trends in neurosciences 29.11 (2006): 632-639.

  2. I noticed you said the woman who was vegetarian didn’t have them in her breast? What was the cause of her breast cancer then? And this obviously means there are other factors that affect breast cancer? Why did the woman who was vegetarian get breast cancer?

  3. I think, it would important to address what types of meats, the amounts, and at what temperature? Does slow cooking in a crock pot have the same effect?

  4. God commanded the Jewish people to eat sacrificial meat which is cooked over the fire. Not only that, but the priests and their families ate this grilled meat daily as payment for their work and as part of the atonement process it was crucial that they eat the meat. Was meat once so very different?

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