Find Information About:

Drugs & Supplements

Get information and reviews on prescription drugs, over-the-counter medications, vitamins, and supplements. Search by name or medical condition.

Pill Identifier

Pill Identifier

Having trouble identifying your pills?

Enter the shape, color, or imprint of your prescription or OTC drug. Our pill identification tool will display pictures that you can compare to your pill.

Get Started

My Medicine

Save your medicine, check interactions, sign up for FDA alerts, create family profiles and more.

Get Started

WebMD Health Experts and Community

Talk to health experts and other people like you in WebMD's Communities. It's a safe forum where you can create or participate in support groups and discussions about health topics that interest you.

  • Second Opinion

    Second Opinion

    Read expert perspectives on popular health topics.

  • Community


    Connect with people like you, and get expert guidance on living a healthy life.

Got a health question? Get answers provided by leading organizations, doctors, and experts.

Get Answers

Sign up to receive WebMD's award-winning content delivered to your inbox.

Sign Up

Breast Cancer Health Center

Font Size

Breast Cancer Risk: Does Soy Help?

Studies Suggest That Eating Soy May Slightly Lower Risk of Developing Breast Cancer
WebMD Health News

April 6, 2006 -- The answer to the question, "Does eating a soy-rich diet lower breast cancer risk?" is an unqualified "maybe," according to the largest analysis of studies ever to examine the issue.

Johns Hopkins and Georgetown University researchers pooled the results of 18 studies and concluded that women who eat soy products may have a slightly lower risk of developing breast cancer than those who don't.

But they also found that inconsistencies and design limitations within the studies raised doubt about soy's cancer prevention benefits.

They warned that high-risk women who take soy supplements, instead of getting soy through food sources, could potentially be doing themselves more harm than good. The data are mixed, but some animal and cellular studies suggest that soy at very high doses can stimulate the growth of estrogen-sensitive breast tumors.

"At this point, women should not be taking high-dose soy supplements, especially those who are breast cancer survivors and women at increased risk for the disease," says researcher Bruce Trock, PhD. Brock is an associate professor at Baltimore's Johns Hopkins' Brady Urological Institute and Kimmel Cancer Center.

East vs. West

Women who live in Asian countries have much lower rates of breast cancer than those living in Western ones. Because this protection is not seen among Asian women who immigrate to the U.S., researchers believe that lifestyle differences -- specifically the difference between Eastern and Western diets -- explain the risk disparity.

Soy-based foods have long been a staple of Asian diets, but they were absent from most American diets until about the last decade.

Soy contains isoflavones, which may have biologic effects that could potentially reduce breast cancer risk. It also has estrogen-promoting properties, which may spur the growth of breast cancers fueled by the hormone.

In an effort to better understand the role of soy in breast cancer risk, Trock and colleagues Leena Hilakivi-Clarke, PhD, and Robert Clarke, PhD, of Georgetown University, combined the results from studies conducted between 1978 and 2004. All were epidemiologic, meaning that participants were asked questions designed to identify their dietary soy exposure and overall breast cancer risk.

Their findings are reported in the April 5 issue of the Journal of the National Cancer Institute.

Today on WebMD

Breast Cancer Overview
From self-exams and biopsies to reconstruction, we’ve got you covered.
Dealing with breast cancer
Get answers to your questions.
woman having mammogram
Experts don’t agree on all fronts, but you can be your own advocate.
woman undergoing breast cancer test
Many women worry. But the truth? Most abnormalities aren’t breast cancer.
Breast Cancer Treatments Improving
Resolved To Quit Smoking
Woman getting mammogram
Screening Tests for Women
ovarian cancer overview slideshow
serious woman
what is your cancer risk
10 Ways to Revitalize Slideshow