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For Immediate Release: November 15, 2012
Contact: AICR Communications Department, communications@aicr.org, 202-328-7744

Soy is Safe for Breast Cancer Survivors

New Review of the Research

WASHINGTON, DC — Breast cancer patients and survivors need no longer worry about eating moderate amounts of soy foods, finds a new review of the research published today on the website of the American Institute for Cancer Research (AICR).

The latest update of the online tool AICR’s Foods That Fight Cancer answers one of the most frequently asked questions relating to how diet may affect breast cancer risk.

“Determining whether it is safe for breast cancer survivors to eat soy has been one of the big research questions under study and now we know it is safe – the evidence is so consistent,” said AICR Nutrition Advisor Karen Collins, MS, RD, CDN, an expert on diet and cancer prevention who worked with AICR to examine the research and develop the materials.

For all cancers, human studies show soy foods do not increase risk and in some cases may even lower it, the review finds.

AICR’s Foods that Fight Cancer™: Soy summarizes both current and emerging evidence on soy and cancer risk. The web-based tool highlights AICR/WCRF’s reports along with the ongoing laboratory, observational and clinical studies. The resource was reviewed by a review committee of leading soy-cancer experts.

Early Fears Allayed

Previous concerns with soy and increased breast cancer risk stem from soy foods’ isoflavones, a group of compounds that in some ways mimic the action of estrogen. High blood levels of estrogen are linked to increased breast cancer risk. These fears were enforced by rodent studies that suggested two isoflavones, genistein and daidzein, led to breast cancer cell growth.

Scientists now know that rodents and most other laboratory animals metabolize soy isoflavones differently than humans. And soy consumption does not lead to increased estrogen levels in humans. Six recent human studies and one major meta-analysis have found that consuming moderate amounts of soy foods does not increase a breast cancer survivor’s risk of recurrence or death.

A moderate amount of soy is one to two standard servings daily of whole soy foods, such as tofu, soy milk and edamame. Studies have demonstrated as many as three servings a day are not associated with increased breast cancer risk.

Some preliminary human studies suggest that soy foods may be most protective among breast cancer survivors who are taking tamoxifen, but this research is ongoing.

For breast cancer risk among cancer-free women, studies on soy consumption either show no link or a slightly protective link to breast cancer. Some research suggests that protective effects may primarily come from consuming soy during childhood and adolescence.

“There are numerous ways in which soy foods may protect against cancer,” notes Collins. Laboratory studies show that soy isoflavones inhibit a number of cell signaling pathways linked to cancer growth. And research suggests some individuals may benefit more from soy’s compounds than others.”

Soy Foods: The Big Picture

AICR estimates that 38 percent of US breast cancer cases every year – approximately 86,000 cases – could be prevented if women were to maintain a healthy weight, be physically active, drink less alcohol and breastfeed their children.

To reduce risk of recurrence and secondary cancers, survivors are encouraged to follow these same recommendations.

Soy foods are among the many plant-based foods that can help women get to and stay a healthy weight, note AICR experts.

“The evidence is not quite there to start saying soy reduces the risk of cancer,” says Collins. “But for breast cancer survivors who want to eat less meat, get protein and enjoy a more plant-based diet, soy is a healthy food and everyone – including breast cancer survivors – can feel comfortable eating it.”

Editor’s Note

AICR’s Foods That Fight Cancer™ is an independent review of the literature and does not receive support from trade associations or food advocacy groups.



The American Institute for Cancer Research (AICR) is the cancer charity that fosters research on the relationship of nutrition, physical activity and weight management to cancer risk, interprets the scientific literature and educates the public about the results. It has contributed more than $95 million for innovative research conducted at universities, hospitals and research centers across the country. AICR has published two landmark reports that interpret the accumulated research in the field, and is committed to a process of continuous review. AICR also provides a wide range of educational programs to help millions of Americans learn to make dietary changes for lower cancer risk. Its award-winning New American Plate program is presented in brochures, seminars and on its website, www.aicr.org. AICR is a member of the World Cancer Research Fund International.

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