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Over the past few years women have been given a lot of conflicting information about consuming soy and its relationship to cancer prevention and cancer development. Wading through the information can be daunting. On one hand, eating soy isoflavones is thought to be beneficial for lowering the risk for cancer, heart disease and diabetes. But those health benefits are clouded by its ability to produce the female hormone estrogen, so for some women there may be no benefit at all.
Researchers have determined that soy isoflavones, naturally occurring compounds found in plants, are in fact weak estrogens that have a similar effect on the body as the female hormone estrogen. In recent years, more menopausal women have turned to soy products to calm their accompanying symptoms as an alternative approach to hormone replacement therapy (HRT).
As consumption of soy products, such as soy milk, fresh and dried soy beans, tofu, tempeh, miso and soy sprouts increases annually, there has been a growing concern within the medical community about the effects soy consumption could be having on women, particularly those with estrogen and progesterone receptor positive breast cancer and endometrial cancer. Estrogen fuels tumor growth in these kinds of cancers.
Chinese researchers at the Harbin Medical University Cancer Hospital followed 524 women who had surgery for breast cancer for five to six years to determine the impact of soy isoflavones on breast cancer patients receiving adjuvant endocrine therapy, typically Tamoxifen or Anastrozole.
The study found post-menopausal breast cancer patients with hormone sensitive cancer lowered their risk of recurrence by consuming high amounts of soy isoflavones, but the results did not translate to pre-menopausal women and there was no increase in survival rates for either group.