DNA-damaging chemicals formed when meat is cooked stimulate breast cancer cells almost as much as pure estrogen and can infiltrate the ducts where most breast cancers arise.
Images thanks to euthman / Flickr
In the 90's two international studies found an association between breast cancer and intake of fried meat and broiled meat in Finland and Uruguay. In 2000 researchers in Iowa identified the probable culprit, a heterocyclic amine abbreviated PhIP. Heterocyclic amines are a class of ubiquitous mutagens found in cooked meats, poultry, fish, and cigarette smoke. The effect was confirmed on Long Island, and extended to grilled barbequed and smoked meats but why more breast cancer risk? Well, these cooked meat carcinogens are mutagenic, meaning they damage DNA; in fact you can directly correlate the number of DNA mutations in breast tissue with estimates of dietary intake. They asked women undergoing breast reduction surgery about their meat cooking methods and found that the intake o processed, fried, and stir-fried meat associated with the number of DNA mutations they found in their breast tissue. But what surprised everyone was that not only may these meat chemicals trigger the original cancer causing mutation, they may then promote the growth of the tumor, as PhIP was discovered to be a potent estrogen. They dripped the kinds of levels of PhIP you'd expect eating cooked meat and found that it activated estrogen receptors almost as powerfully as straight estrogen, and that’s what they saw when they tried it on breast cancer cells. They found it proliferative potency approaching that of to pure estrogen. They conclude that PhIP possesses estrogenic activity at low concentrations … supporting the idea that exposure to PhIP, even at low doses, could result in estrogenic effects. We suggest that the well-established and unequivocal genetic toxicology of PhIP coupled with its estrogenic activity could drive clonal expansion and promote growth of the initiated phenotype. These were 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. We didn't know for sure, until this study, which measured the levels of PhIP in the breast milk formed in those ducts of nonsmoking women, and the average concentration they found, was point one nanomoles per liter, right here, significant proliferative potency. One of the women was vegetarian, though, and of course none was detected in her breast milk.
To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring watch the above video. This is just an approximation of the audio contributed by Jonathan Hodgson.
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This is the first of a four-part video series on heterocyclic amines, these DNA-damaging chemicals formed in cigarette smoke and when mammal, bird, and fish muscles are cooked. I've covered them previously in my videos Muscle Tremors & Diet, Fast Food Tested for Carcinogens, and Carcinogens in Roasted Chicken?
Carcinogens tend to either initiate or promote cancer, rarely both. Not only may heterocyclic amines trigger the original mutation and help the tumor grow, they may also aggravate cancer invasiveness, the subject of the next video PhIP: The Three Strikes Breast Carcinogen.
Please also check out my associated blog posts for more context: Mushrooms for Breast Cancer Prevention, Estrogenic Chemicals in Meat, Avoid Cooked Meat Carcinogens, Foods That May Block Cancer Formation, Should We Avoid Titanium Dioxide?, and Breast Cancer & Alcohol: How Much Is Safe?