WEDNESDAY, Nov. 2, 2005 (HealthDay News) -- Diets high in the natural plant estrogens found in soy won't increase the risk of uterine cancer in postmenopausal women, new research suggests.
The results of human and animal studies "give us some confidence that dietary soy doesn't promote uterine cancer and, in fact, may offer a protective effect in some cases," Dr. Mark Cline, associate professor of comparative medicine at Wake Forest University Baptist Medical Center, said in a prepared statement.
He summarized the findings from the studies, which were funded by grants from the U.S. National Institutes of Health and the Solae Company, which sells soy products.
There's conflicting evidence about whether high levels of dietary soy are safe for postmenopausal women. Soy contains estrogen-like compounds called isoflavones. Many women have turned to soy as a natural alternative to hormone replacement therapy (HRT), after long-term use of HRT was linked to an increased risk of breast cancer and stroke.
Last year, Italian researchers reported that some women who took soy tablets for up to five years had an increased occurrence of endometrial hyperplasia, a condition where the lining of the uterus grows too much. The condition can be a precursor of uterine cancer.
"This observation from this study and its interpretation should be carefully considered. Both human observational studies and several short-term trials of soy isoflavones have not shown any proliferation-inducing effect of soy isoflavones on the uterus," Cline said.
He noted that preliminary results of a two-year study of women who consumed 58 milligrams of soy isoflavones a day show no relationship between soy and endometrial proliferation. And research in monkeys found those that received soy isoflavones at dietary doses for the equivalent of 10 human years showed no increased risk of endometrial hyperplasia.
The findings were to be presented Wednesday in Chicago at the Sixth International Symposium on the Role of Soy in Preventing and Treating Chronic Disease.
More information
The U.S. Food and Drug Administration has more about soy.
