A new study to be presented in early June at the American Society of Clinical Oncology annual meeting in Chicago has reported that U.S. chicken and beef contain relatively high levels of estrogen. Estrogen has been reported to contribute to the incidence of hormone-dependent cancers in women. However, there appears to be very little discussion concerning dietary estrogen from meat in relation to cancer incidence. In the study, concentrations of estradiol-17β (E2) and estrone (E1) were measured in beef produced in the U.S. and Japan (40 samples each), and chicken produced in the U.S., Japan, and Brazil (25 samples each). Fat and muscle meat were examined separately. For comparison, the authors also analyzed fat tissues of 25 postmenopausal Japanese women.

Estrogen levels were found to be higher in fat than in muscle meat. Median concentrations (picograms per gram (pg/g)) of estrogen in Japanese chicken fat (E2 = 21.1, E1 = 65.7) and in U.S. chicken fat (20.7, 54.6) were the highest of the samples assessed. U.S. beef fat also had a relatively high level (14.0, 7.7). However, Japanese beef red meat (0.0, 0.1) and Brazilian chicken muscle meat (0.2, 0.4) were found to incorporate nearly zero levels of estrogen, and the estrogen levels in their fat were also low. The high E2 levels in Japanese and U.S. chicken exceeded the levels found in the fat of Japanese women (16.3). On the other hand, levels in meat with low estrogen content were a hundred times lower than in human fat.

The authors comment that the high estrogen concentrations in Japanese and U.S. chicken, as well as U.S. 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 may be considered the natural amount found in meat without estrogen supplementation. The estrogen levels found in U.S. chicken and beef are much lower than those of birth control pills. However, estrogen intake from meat consumption cannot be dismissed as a factor governing human health, according to the authors, considering lifetime exposure to such meat. The authors conclude that dietary estrogen intake from meat might promote estrogen accumulation in the human body and could influence the incidence of hormone-dependent cancers.

Estrogen in chicken comes mainly from feed

Some may find the study results surprising with respect to chicken since currently there no hormones approved by the U.S. Food and Drug Administration (FDA) for poultry. However, estrogen may be introduced in the form of soy protein and animal protein meal in chicken feed and possibly other sources. Based on the available evidence, breast cancer patients, survivors and those at high risk should consider avoiding beef and pork and limited their poultry consumption to organically grown birds, preferably raised without soy-based feed and in humane conditions.