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Does dietary estrogen intake from meat relate to the incidence of hormone-dependent cancers-
Background: It is well known that estrogen contained in contraceptive pills has a relationship with the incidence of hormone-dependent cancers. Conversely, there appears to be very little discussion concerning dietary estrogen from meat in relation to cancer incidence despite the fact that beef and chicken of most daily diets comes from animals fed with estrogen supplements. Thus, we evaluated estrogen concentrations in meat. Methods: Intra-tissue concentrations of Estradiol 17 Beta (E2) and Estrone (E1) were measured in beef (produced in USA, Japan: n = 40, 40) and chicken (produced in USA, Japan, Brazil: n = 25, 25, 25) by LC-MS/MS. Fat and red meat were examined separately in each meat. As a control we also analyzed fat tissues of postmenopausal Japanese women (n = 25). Results: Estrogen levels were generally higher in fat than in red meat. Median concentrations (pg/g) in Japanese chicken fat (E2 = 21.1, E1 = 65.7) and in USA chicken fat (20.7, 54.6) were the highest, and USA beef fat (14.0, 7.7) also showed high level. On the other hand, Japanese beef red meat (0.0, 0.1) and Brazilian chicken red meat (0.2, 0.4) indicated nearly zero level of estrogen, and their estrogen levels in fat were low as well. The high estrogen levels in Japanese and USA chicken, especially that of E2, exceeded those of human fat (16.3, 157.1), while the levels in meat of low estrogen content were a hundred times lower than in human fat. Conclusions: The high estrogen concentrations in Japanese chicken, USA chicken, and USA beef have been attributed to the residue of external estrogen in the feed given to the livestock. The nearly zero level found in Japanese beef and Brazilian chicken is considered to be natural endogenous amount without estrogen supplementation. The estrogen levels in meat are much lower than those of contraceptive pills (0.035 mg/tab). Even so, when considering lifetime exposure to meat containing higher level of estrogen than human fat tissue, estrogen intake from daily meat consumption cannot be disregarded as a factor governing human health. Consequently, dietary estrogen intake from meat might promote estrogen accumulation in the human body and could be related to the incidence of hormone-dependent cancers.