Is Soy Detrimental for Women with Breast Cancer?

What You Need to Know: Two weeks of soy supplementation was enough to increase expression of genes related to tumor proliferation.  Women with breast cancer should probably not take soy supplements, and should eat soy foods, such as tofu and tempeh, only in moderation.

The Study: Jacqueline Bromberg, M.D., Ph.D., a breast cancer specialist at the Memorial Sloan Kettering Cancer Center in New York City, and colleagues randomly assigned 140 women with newly diagnosed, early-stage breast cancer to one of two groups. In one, women took a soy protein supplement every day for anywhere from one to four weeks; those in the other group were given milk powder as a comparison. The women were premenopausal or just past menopause. The soy supplement — a powder added to water or juice — was the equivalent of about four cups of soy milk a day. Women in the study typically used it for two weeks.

Results: Researchers found that about 20 percent of the women using soy developed high blood concentrations of genistein, a soy phytoestrogen. Among those women, some showed heightened activity in certain genes that promote breast tumor growth and spread.

“This study doesn’t tell us anything about whether soy raises the risk of developing breast cancer,” said Bromberg who also noted there was no evidence of “tumor proliferation” in women with revved-up gene activity, but the study may have been too short to detect such an effect. “All we can say is that two weeks of soy supplementation was enough to increase expression of genes related to tumor proliferation.” But to be safe, she said, women with breast cancer should probably not take soy supplements, and should eat soy foods, such as tofu and tempeh, only in moderation.

My Take: There are conflicting reports on the impact of soy on breast carcinogenesis. This study examines the effects of soy supplementation on breast cancer-related genes and pathways. While the study proves little, it seems prudent (for those with a history of breast cancer) to avoid soy supplements, and to consume soy-based foods in moderation. I’m Dr. Michael Hunter.

The small print: The material presented herein is informational only, and is not designed to provide specific guidance for an individual. Please check with a valued health care provider with any questions or concerns. As for me, I am a Harvard- , Yale- and UPenn-educated radiation oncologist, and I practice in the Seattle, WA (USA) area. I feel genuinely privileged to be able to share with you. If you enjoyed today’s offering, please consider clicking the follow button at the bottom of this page.

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References: 1. Jacqueline Bromberg, M.D., Ph.D., physician/scientist, Memorial Sloan Kettering Cancer Center, New York City; V. Craig Jordan, Ph.D., D.Sc., scientific director, Lombardi Comprehensive Cancer Center, Georgetown University, Washington, D.C.; Sept. 4, 2014 Journal of the National Cancer Institute; 2.  http://consumer.healthday.com/cancer-information-5/breast-cancer-news-94/soy-a-friend-or-foe-of-breast-cancer-691425.html

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understandcancerin60minutes

Harvard AB Yale MD UPenn Radiation Oncology Radiation Oncologist, Seattle area

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