Breast Cancer and Soy Product

When I treat breast cancer patients, they often ask the question: should I avoid soy products? In the past, oncologists would warn that breast cancer patients should not consume soy products, especially women with apositive estrogen receptors. I have read many articles about how Asian women are less prone to develop breast cancer than Caucasian women, especially Japanese women who eat a lot of Tofu and Tempei. Soy products do contain phytoestrogen, but it is very weak and belongs to the good estrogen category called estriol, which prevents breast cancer according to a study done by Dr. Henry Lemon. When your body has a very low level of estrogen, the phytoestrogen can combine with the estrogen receptor and serve as estriol. When your body has a lot of bad estrogen, such as estradiol or estrone, which can stimulate breast tissue growth, phytoestrogen can occupy part of the receptors to block the stimulating effect. The following research shows evidences that phytoestrogen can help cancer patients instead of harming them.

In Am J Clin Nutr. 2012, Nechuta SJ, et al, included 9514 breast cancer survivors with a diagnosis of invasive breast cancer between 1991 and 2006 from 2 US and 1 Chinese cohort. Soy isoflavone intake (mg/d) was measured with validated food-frequency questionnaires. The research found that consumption of more than 10 mg isoflavones per day was associated with a nonsignificant reduced risk of breast cancer-specific mortality and a statistically significant reduced risk of recurrence of breast cancer. Zaineddin AK of Germen Cancer Research Center conducted a population-based case-control study in German postmenopausal women to evaluate the association of phytoestrogen-rich foods and dietary lignans with breast cancer risk. Dietary data were collected from 2,884 cases of breast cancer and 5,509 controls using a validated food-frequency questionnaire. This research indicated that high and low consumption of soybeans as well as of sunflower and pumpkin seeds were associated with significantly reduced breast cancer risk compared to no consumption. The observed associations were not differential by estrogen receptor status. No statistically significant associations were found for dietary intake of plant lignans and fibers. These results provide strong evidence for a reduced postmenopausal breast cancer risk associated with increased consumption of sunflower, pumpkin seeds and soybeans.

Li Zheng is a licensed acupuncturist and herbalist, a graduate of the Beijing University of Chinese Medicine with 24 years of clinical and research experiences, including 6 years of residency, a Ph.D. degree holder in medical sciences from the US, a Harvard Medical School trained researcher and a professor at the New England School of Acupuncture. Her website is and her clinic is located at 475 hillside avenue, Needham, MA02494.