Update on the soy debate

updates

Previous fears that soy-rich diets contribute to breast cancer have been eased. In fact, according to the new research, soy could actually reduce a woman's odds of developing the disease.

It was once believed that consumption of tofu, soybeans and soy milk lowered the incidence of dense breast tissue, which is considered a high risk for breast cancer.

Then some scientists hinted that the estrogenic compounds in soy might interfere with hormone levels and encourage the growth of breast tumors. While the debate lacked scientific evidence, many women backed away from soy.

However, according to new research from three institutions-- Cancer Research UK, based in London; the National University of Singapore; and the National Cancer Institute in Bethesda, Maryland-soy could help reduce a woman's odds of developing breast cancer.

The scientists analyzed the results from two previous studies carried out in Singapore: one that researched women's diets and another that analyzed breast tissue density.

In the researchers' news release, women who ate the most soy were 60 percent less likely to have the high-risk breast tissue than women who consumed the least soy.

The researchers believe that the benefit could come from a compound in soy called isoflavone, which mimics the action of the female hormone estrogen.

Although such phytoestrogens (plant-based estrogens) are not as strong as the estrogen that the body produces, they appear to lengthen a woman's menstrual cycle. Previous studies show that the fewer menstrual periods a woman has in her lifetime, the lower her risk of breast cancer.

"These findings make an important contribution toward our ongoing studies on the relationship between diet and cancer, and they may eventually point to new ways of preventing breast cancer," says Sir Paul Nurse, Interim Chief Executive of Cancer Research UK.

The new study supports the results of an April 2000 study at the University of Toronto's department of Nutritional Sciences, where researchers found that soy poses no higher risk of breast cancer.

David Jenkins, PhD, who led the Toronto study, says, "The concern had been whether soy estrogen might actually lead to hormone-dependent breast cancer, but our researchers found no evidence of this."