• Home
• Womens Health

• Choose text size:
• A
• A
• A

February 19, 2010 | Comments: 3

The Truth About Soy and Breast Cancer

Will eating soy reduce the risk of breast cancer, as some studies suggest? Or might it promote and/or fuel breast cancer, as others warn?

In Asia, women who eat soy foods regularly have much lower rates of breast cancer than Western women, and when they move to the U.S., their rates go up. Researchers hypothesized that something in soybeans may be protective against breast cancer, and their search led them to compounds called isoflavones, plant estrogens that have weak hormonal effects. In lab studies, isoflavones exert a variety of anti-cancer effects.

While this sounds promising, no one knows if soy actually reduces breast cancer risk. Some lab and animal studies suggest that soy’s estrogenic properties could increase breast cancer risk. And the few well-controlled studies that have tracked women’s soy intake and later development of breast cancer have had inconsistent or inconclusive results.

Some points to keep in mind:

• Soy’s effects on breast cancer may depend on when in life it is consumed. Japanese women eat soy throughout life, whereas most American women may have only started eating it in recent years as adults. It’s been proposed that isoflavones act as anti-estrogens in premenopausal women who have high circulating hormone levels. But after menopause, when estrogen levels are low, they may act like estrogens. And any estrogen boost, even if weak, may, at least theoretically, be harmful in such women.

• Soy’s effects in women with breast cancer or those at high risk are unknown. Some preliminary research, though, suggests it may not be as risky as previously feared. If you have or have had breast cancer, the American Cancer Society says you can consume moderate amounts of soy, but should avoid high intakes.

• The optimal amount of dietary soy for breast cancer protection is unknown. The Japanese eat one or two servings a day, on average, and higher amounts might not reduce breast cancer risk further. Moreover, different forms of soy may have different effects.

• There’s little research on breast cancer and soy supplements, which contain concentrated isoflavones and/or soy protein. Most studies have been done on animals or in test tubes.

Bottom line: A moderate amount of soy (one or two servings a day) can be part of a healthy diet. Soy is a good food, especially if it replaces less healthful foods in your diet, such as fatty meat. It’s rich in plant protein, healthful unsaturated fats, fiber, and sometimes calcium. But don’t count on soy to prevent or cure breast cancer. No food can. On the other hand, soy is not likely to cause breast cancer either, and you need not be afraid to eat it.

Read more on this topic