Soyfood consumption and the risk of breast cancer has been a controversial topic. And this Breast Cancer Awareness Month, we’re here to share the current research, which has found that eating soyfoods is safe for both healthy individuals as well as breast cancer survivors. The science shows soyfood consumption is not linked with developing breast cancer or breast cancer recurrence, and, in reality, soyfood consumption has been linked to a reduction in breast cancer risk.
The American Cancer Society says, “For the breast cancer survivor, current research finds no harmful effects from eating soy foods. These foods may even help tamoxifen work better.”
Another top cancer-fighting association, the American Institute for Cancer Research, reviewed all the latest research in 2012 and maintained its stance that soyfoods are not only safe but “contain several key nutrients and phytochemicals studied for their cancer prevention properties.”
Myth: Soyfoods are not safe for women at risk of developing breast cancer or breast cancer survivors because they contain estrogen.
Truth: Research shows that women who are at risk for developing breast cancer or who are breast cancer survivors can safely consume moderate amounts of soyfoods. A review of more than 130 human research trials and meta-analyses published in peer-reviewed journals since 1998(1-6) indicates that soyfoods do not cause tumors in breast tissue and do not have significant effects on those at risk of getting breast cancer.
Hearing conflicting messages in the media can be confusing, but it’s important to look at the science. Human research trials have not demonstrated any link between eating soyfoods and tumor growth. Where the conflicting information comes from are a couple studies done on animals that have indicated soy might increase the chances of breast cancer recurrence because soy contains isoflavones.(7,8) Isoflavones are often described as phytoestrogens because they are found in plants (phyto) and are structurally similar to human estrogens. Isoflavones are much weaker than naturally circulating human estrogens, as they have approximately 1/1000th the biological activity of circulating human estrogens, and therefore do not have estrogen-like effects in humans. Furthermore, the levels of isoflavones given to mice in these studies were at enormously higher than levels found in traditional soyfoods. People who eat a balanced diet rich in soyfoods would not come close to consuming isoflavone levels as high as those used in these experiments on animals.
Soyfoods are safe for breast cancer survivors. Soyfoods do not appear to increase the risk of breast cancer recurrence among survivors of the disease. (9-17) The American Cancer Society recommends that breast cancer survivors can safely consume moderate amounts of soyfoods – anywhere from a few servings per week to 3 servings per day.(17)
Soyfoods may reduce the risk of developing breast cancer. Research has found that women who eat soyfoods regularly are less likely to develop breast cancer, compared to those who don’t. Soyfoods consumption may reduce the risk of breast cancer especially when soy is consumed during childhood and adolescence.(18-20)
Researchers at the University of Southern California found women averaging one cup of soymilk or about one-half cup of tofu daily have a 32% less risk of developing breast cancer and a 29% decreased risk of death, compared with women who ate little or no soyfoods.(21)
Breast cancer is a very complex disease and risk may be dependent on multiple factors. As always, it is important to eat a healthy diet, get physical activity and maintain medical checks for overall health and breast cancer prevention.
Links worth checking out
- More research on the links between Soy and Breast Cancer
- More research on Soy and Breast Cancer Survivors
- American Cancer Society discussion on the properties and health benefits of soy
- American Cancer Society information on health and lifestyle choices during and after cancer treatment including the safety of soyfoods for breast cancer survivors
- The Soy and Breast Cancer Conundrum from Eating Well magazine
- Video: What Is the Relationship Between Soy and Breast Cancer?
- Health Benefits of Soy press release from the Soy Nutrition Institute
As always be sure to check us out on Facebook, Twitter and Pinterest for more great recipes and interesting facts about soyfoods. Check out our YouTube page featuring with videos hosted by food and nutrition expert Rebecca Scritchfield, RD.
1. Maskarinec G, Morimoto Y, Conroy SM, Pagano IS, Franke AA. The volume of nipple aspirate fluid is not affect by 6 months of treatment with soy foods in premenopausal women. J Nutr 2011;141:626-30.
2. Maskarinec G, Takata Y, Franke AA, Williams AE, Murphy SP. A 2-year soy intervention in premenopausal women does not change mammographic densities. J Nutr 2004;134:3089-3094.
3. Brown BD, Thomas W, Hutchins A, Martini MC, Slavin JL. Types of dietary fat and soy minimally affect hormones and biomarkers associated with breast cancer risk in premenopausal women. Nutr Cancer. 2002;43:22-30.
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