 In the 1990s, 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 FIP. 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, barbecued, 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 human breast tissue with estimates of dietary intake. They asked women undergoing breast reduction surgery about their meat cooking methods, and found that the intake of processed fried and stir-fried meat were correlated with the number of DNA mutations they found subsequently in their breast tissue. But we already knew these chemicals damaged DNA. 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 ensuing tumor as FIP was discovered to be a potent estrogen. They dripped the kinds of levels of FIP you'd expect in your body after eating cooked meat, and found that it activated estrogen receptors almost as powerfully as straight estrogen. And that's what they found when they tried it on breast cancer cells. They found its proliferative potency on human breast cancer cells approaching that of pure estrogen. They concluded that FIP possesses estrogenic activity at low concentrations, supporting the idea that exposure to FIP, even at low doses, could result in estrogenic effects. We suggest that the well-established and unequivocal genetic toxicity of FIP coupled with its estrogenic activity could drive clonal expansion and promote growth of the initiated initial cancer cell. These were breast cells in a Petri dish, though. I mean, how do we know these carcinogens make it from cooked meat not only into the breast after you eat it, 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 FIP in the breast milk formed in those ducts of non-smoking women. And the average concentration they found in the breast milk of meat-eating women corresponds to about right here on this graph, significant breast cancer cell growth potential. One of the women was vegetarian, though, and of course none was detected in her breast milk.