Is Soy Safe for Breast Cancer Survivors?

If you're a breast cancer survivor, you are already aware of the debate about hormone replacement therapy and its potential dangers. But have you ever wondered about the risk soy and other isoflavone-rich foods pose? Some scientists have, and their findings are, to say the least, provocative.

What Soy Isoflavones Are

Isoflavones are plant-made chemicals that belong to a group of compounds called phytoestrogens. In the human body, phytoestrogens mimic the effect of the hormone estrogen. While a number of foods contain isoflavones, soybeans and other soy products are the richest source of isoflavones in the human diet.

Breast Cancer, Soy & Asian Women

In North America, the average daily intake of isoflavones is less than 2 mg. per day. By contrast, in Asia, isoflavone intake may approach 50 mg. per day. But the differences don't stop there. Women in Asia also have significantly lower rates of breast cancer. Is soy responsible? Probably, but not in the way you might think.

Despite the glaring differences between Asian women and North American women, most studies looking at the potential link between breast cancer and soy isoflavones have not found that soy-rich diets offer any protection against breast cancer--with one exception.

There is some evidence that a soy-rich diet during adolescence, when breast tissue is being formed, may offer at least some life-long protection against breast cancer. A growing number of natural health experts, including Dr. Andrew Weil, now recommend isoflavone-rich foods like soy to young girls.

Can Soy Isoflavones Cause Breast Cancer To Return?

If soy isoflavones don't offer any protection against breast cancer, could their estrogenic properties actually cause it? Scientists aren't sure. A growing body of evidence seems to prove that soy isoflavones may help many women better deal with the hot flashes and other symptoms of menopause. And if the estrogenic effects of soy can do that, what's to stop them from encouraging the growth of estrogen-dependent breast cancers?

In 1896 a doctor named George Beatson demonstrated that by removing a woman's ovaries, he could directly reduce her risk of breast cancer. Dr. Beatson's research led to the discovery that many--but certainly not all--breast cancer tumors were estrogen-dependent. A half-century later, this led to the discovery that a woman's risk of breast cancer recurrence could be further reduced by the drug tamoxifen, a failed contraceptive that keeps estrogen production in check.

Does all this mean that women at risk for breast cancer, or a recurrence of breast cancer, should avoid phytoestrogens like the isoflavones in soy foods? Doctors simply don't know but this is a question that every woman should discuss with a qualified health professional.

Should You Avoid Soy If You've Had Breast Cancer?

The link between soy isoflavone and breast cancer, if there actually is one at all, is highly controversial and likely will be for years to come. If you have any questions about phytoestrogens, breast cancer or soy products, talk to your primary health care provider. Only your doctor can evaluate your risk for breast cancer. He or she can help you wade through the volumes of conflicting information and give you the advice that's right for you.

REFERENCES:

Higdon, J. (2006). Soy Isoflavones. Retrieved on May 22, 2007 from http://www.http://lpi.oregonstate.edu/infocenter/phytochemicals/soyiso/

Journal of Experimental Medicine. (2007). Hormones and Breast Cancer: Controlling The Danger Within.