In some studies scientists report finding tamoxifen-like substances in soybeans that may block tiny "seeds" of estrogen-dependent breast cancer early in the disease process, before estrogen receptors have had a chance to go bad.

Stephen Barnes, a pharmacologist at the University of Alabama at Birmingham, and his colleagues reported results on rats, suggesting that a tamoxifen look-alike found in soybeans may block cancer at an early stage, presumably when the estrogen receptors still function. They say their findings may help explain why Japanese and Chinese women who eat lots of soy-rich foods have a much lower incidence of breast cancer than women do in the United States.

Rats eating the most soy had the fewest breast tumors. Barnes tentatively attributes these results to a compound called genistein, which is found in soybeans and which resembles estrogen and tamoxifen in structure. Like tamoxifen, genistein may discourage tumor growth by blocking estrogen receptors, he speculates. (Barnes S et al: Soy creates compound genistein, Science News 137: 19, 1994.)

In the University of Texas Lifetime Health Letter, September 1994, it was reported that Dr. Barnes and his colleagues are studying a group of phytochemicals known as isoflavones, which are chemically similar to estrogen. In an ongoing clinical study, the investigators hope to identify certain blood and tissue proteins that may serve as cancer markers ("red flags" that may signal cancer). Then they will evaluate the effects of the soy extracts on the markers.