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In The News:
Should Breast Cancer Survivors Eat Soy?

For Immediate Release: December 11, 2009
Contact: Glen Weldon 202-328-7744 x312

Previous lab studies, which suggested that soy might exhibit some estrogen-like activity, have made many breast cancer survivors wary of soy foods for fear it will lead to recurrence. Yet now, a large population study in Chinese breast cancer survivors suggests just the opposite: Eating larger amounts of soy foods was linked to a lower risk of recurrence and death.

The study, published in December’s Journal of American Medical Association, analyzed data from approximately 5,000 Chinese breast cancer survivors, ages 20 to 75. After tracking the women for an average of almost 4 years, the researchers found that the higher a woman's intake of soy foods, the lower her chances of cancer recurrence and death. This association held for cancers that were both estrogen-positive and estrogen negative.

Soy food intake above 11 grams of soy protein (4 oz tofu, 1/2 cup edamame, 1 1/4 cup soy milk) did not show additional benefit.

Soy Questions

Questions on soy and breast health stem from animal and population studies. Early soy research found a protective link between soy and breast health in Asian populations, where soy food is common. Soy contains isoflavones, which were found to have estrogen-like properties in animal studies. Some effects of isoflavones were found to block cancer.

Yet when studies showed estrogen could promote tumor development, concerns about soy foods heightened. There were also fears that soy may counteract the effects of tamoxifen, an anti-estrogen treatment.

AICR ‘s Bottom Line: No Magic Bullet

This latest study may help squelch the fears of those who avoid soy foods completely. But more studies are needed before researchers will know how the consumption of high amounts of soy might impact breast cancer recurrence.

In an editorial accompanying the study, researchers point out several concerns with the study, such as differences between Chinese and U.S. soy food and screening rates, along with the relatively short length of the study (average of 4 years).

Also, some research suggests that eating soy early in life, such as Chinese adolescents do, may be what produces a protective effect in breast health decades later.

Women should note that the protective effects were confined to soy foods, not supplements. For now, AICR’s recommendations remain the same for women including breast cancer survivors:

  • It is safe to eat moderate amounts of soy food (soy milk, tofu) — up to two to three servings per day.
  • As a precaution, women receiving anti-estrogen treatments should minimize soy foods and avoid isoflavone supplements.
  • Evidence still does not support adding soy to your diet hoping that it will help prevent breast cancer. But soy is a healthful food. It is low in saturated fat, high in nutrients, fiber and antioxidants.

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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 $96 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 part of the global network of charities that are dedicated to the prevention of cancer. The WCRF global network is led and unified by WCRF International, a membership association that operates as the umbrella organization for the network. The other charities in the WCRF network are World Cancer Research Fund in the UK (www.wcrf-uk.org); Wereld Kanker Onderzoek Fonds in the Netherlands (www.wcrf-nl.org); World Cancer Research Fund Hong Kong (www.wcrf-hk.org); and Fonds Mondial de Recherche contre le Cancer in France (www.fmrc.fr).

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