Women with breast cancer who eat more soy are less likely to die or have a recurrence of cancer than women who eat few or no soy products, according to a new study.

In the past, physicians have often warned breast cancer patients not to eat soy. The new research represents “a complete turnaround” from the previous understanding about the link between soy consumption and breast cancer, says Sally Scroggs, a registered dietician and senior health education specialist at M.D. Anderson’s Cancer Prevention Center in Houston, Texas.

“We have gone from saying, ‘No soy for breast cancer survivors’ to, ‘It’s not going to hurt,’” Scroggs says. “Now it looks like we can say, ‘It may help.’”

The study looked at more than 5,000 women in China who had undergone a mastectomy; they were followed for about four years. The women who consumed the most soy protein (about 15 grams or more a day) had a 29 percent lower risk of dying and a 32 percent decreased risk of breast cancer recurrence compared to the women who consumed less than about 5 grams of soy protein a day, according to the study, which appears in the December 9 issue of the Journal of the American Medical Association. The National Cancer Institute and the U.S. Department of Defense’s Breast Cancer Research Program funded the study.

Women who ate between 9.5 and 15 grams of soy protein saw nearly the same decrease in risk as the women who ate more than 15 grams. In fact, the researchers found no additional benefits to eating more than 11 grams of soy protein a day. (An 8-ounce glass of soy milk and a cup of shelled edamame contain about 7 and 14 grams of soy protein, respectively.)

In all, 534 women had a breast cancer recurrence or died from breast cancer during the study period.