"This is convincing evidence that at dietary levels, the estrogens found in soy do not stimulate cell growth and other markers for cancer risk," said Charles E. Wood, D.V.M., lead researcher, from Wake Forest University Baptist Medical Center. "The findings should be especially interesting to women at high risk for breast cancer who take soy products."
The research is reported in the current issue of The Journal of Clinical Endocrinology & Metabolism.
Wood said there has been much debate about whether high levels of dietary soy are safe for postmenopausal women. Soy products are sold as a natural alternative to traditional hormone therapy. The most common form of hormone therapy, estrogen plus a progestin, has been shown to increase risk of breast cancer. Soy and some other plants contain estrogen-like compounds called isoflavones or phytoestrogens.
These plant estrogens are thousands of times weaker than the estrogen produced by the body, but may be present in much higher concentrations in the blood. Evidence about their safety has been mixed. It is known that populations that typically consume diets high in soy have lower rates of breast cancer. On the other hand, some studies have shown that soy isoflavones can stimulate breast cancer cells grown in the laboratory.
"Evidence from observational studies in women indicates that soy intake may help prevent breast cancer," said Wood. "But there has still been reluctance to conduct research studies in women because of concerns that isoflavones may stimulate breast cell growth and increase the risk of breast cancer."
Wood and colleagues measured how a diet high in soy isofllavones affected markers for breast and uterine cancer risk in postmenopausal monkeys. The monkeys ate one of
Contact: Shannon Koontz
Wake Forest University Baptist Medical Center