Soy and Breast Cancer

If you’ve had breast-cancer, you may have been told not to eat soy foods. The concern: isoflavones in soybeans, natural compounds that act like very weak forms of estrogen, could increase the chance of a recurrence. But according to the largest ever study on soy and breast cancer, a regular intake of soy actually reduces the risk of the cancer returning.

The study from the American Journal of Clinical Nutrition, followed 9,514 breast-cancer survivors from the United States and China for eight years. Women whose daily diets provided 10 milligrams or more of soy isoflavones had a 25-per-cent lower risk of recurrence compared to those who consumed less than four milligrams daily.

Some experts have also worried that soy foods might diminish the effectiveness of tamoxifen, a drug used to prevent breast-cancer recurrence in women with certain types of the disease.

However, the researchers found that tamoxifen users with higher soy-isoflavone intakes had a lower risk of breast-cancer recurrence than women who did not take the drug and who consumed the lowest amount of isoflavones.

So how do you get those 10 milligrams a day? Two tablespoons of soybeans, two teaspoons of soy nuts, ¼ cup firm tofu, and ½ cup of soy beverage all have about that amount.

By the way, these findings apply soy foods, not isoflavone supplements. There’s no data how safe those are.