Women who are diagnosed with breast cancer are often advised to avoid exposure to estrogen. That includes prescription drugs such as Premarin or Prempro as well as bio-identical hormones.
Researchers have long wondered whether it is safe for these women to eat soy-based foods because soy has estrogenic activity. A study of more than 5,000 breast cancer survivors in Shanghai, China, found that the women who ate the most soy were least likely to die of their cancer or have a recurrence. After 4 years, 7.4 percent of those who consumed the equivalent of three cups of soy milk daily had died of breast cancer. Women who ate the least soy, equivalent to about one-half cup of soy milk daily, had a 10.3 percent mortality rate during the 4 years. Experts advise against consuming excessive amounts of soy, particularly as supplements such as genistein. Studies in test tubes suggest that genistein can boost breast tumor proliferation.
