Soy Appears Safe for Breast Cancer Survivors
Moderate Intake of Soy Reduced Breast Cancer Death Risk, Recurrence in Study
Soy and Breast Cancer: Study Results continued...
Women in the lowest soy protein group ate less than 5.31 grams of soy
protein daily and about 20 milligrams of isoflavones, while those in the
highest ate more than 15.31 grams of soy protein and more than 62.68 milligrams
But the benefits of soy leveled off, Shu tells WebMD. "After 11 grams of soy
protein a day, ''we don't see additional benefits."
"That is about 1/4 cup of firm tofu or 1.5 cups of soy milk,'' she says.
"This is a moderate intake."
Of her findings, "I think it's generalizable to the American population,"
Shu tells WebMD. She points to a study published in November, in which U.S.
researchers found in an analysis of nearly 2,000 U.S. breast cancer survivors
that soy isoflavones consumed at levels comparable to those in Asian
populations may reduce breast cancer recurrence in women getting tamoxifen
Shu's study was funded by the U.S. Department of Defense Breast Cancer
Research Program and the National Cancer Institute. She reported receiving a
research development fund from the United Soybean Board in 2005.
Soy and Breast Cancer: Other Opinions
The new study is strong and scientific, says Rachel Ballard-Barbash, MD,
MPH, associate director of the Applied Research Program at the National Cancer
Institute in Bethesda, Md., who co-authored the editorial. But "the amount
of soy food consumed in China is much higher than in the U.S."
That's a point that Shu also makes, writing that the average isoflavone
intake in U.S. women is 1 to 6 mg a day, compared with 47 mg a day in the
''It's not quite clear how this [study] extrapolates to U.S. women,"
''Other differences in these populations may at least partly explain the
results," says Marji McCullough, ScD, an American Cancer Society epidemiologist
in an email after reviewing the study. ''For example, it is likely that Chinese
women have regularly consumed soy throughout their lifetime, whereas in the
U.S. consumption is much less common. We don't know whether starting to eat soy
regularly after a cancer diagnosis would have the same effect as having a
lifelong diet high in soy foods."
What's a breast cancer survivor to do? Moderation may be best. "We think
it's unlikely that occasional consumption of soy-based food in the diet would
be detrimental," Ballard-Barbash says.
''The study is consistent with our current guidelines for breast cancer
survivors, which state that consumption of up to three servings of soy foods
per day as part of a healthy diet is safe," McCullough says.
Avoiding high doses such as those found in soy powders and isoflavone
supplements should be avoided, she says, because of their possible