Soy products and breast cancers

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From Medscape:

From Reuters Health Information

Soy Safe for Women Who Have Had Breast Cancer

By Fran Lowry

New York (Reuters Health) Apr 06 - Soy foods do not increase the risk of

recurrence or death in women who have had breast cancer, according to a

meta-analysis presented this week at the 102nd annual meeting of the American

Association for Cancer Research.

" Women who currently consume soy food can be reassured that their soy food

consumption in moderation does not increase risk of breast cancer

recurrence, " lead researcher Dr. Xiao Ou Shu, from Vanderbilt University

Medical

Center, Nashville, Tennessee, told Reuters Health.

" Women who want to adopt a healthy lifestyle to improve their breast cancer

prognosis and overall health can include moderate soy food consumption as

part of a healthy diet. "

Women and their doctors have long worried that soy isoflavones might

increase the risk of cancer recurrence because of their estrogen-like

properties,

including the ability to bind to estrogen receptors in the breast and

stimulate cellular proliferation.

Also, Dr. Shu notes, there have been conflicting reports of synergistic and

antagonistic effects between isoflavones and tamoxifen, both of which bind

to estrogen receptors.

To learn more, Dr. Shu and colleagues used data from the After Breast

Cancer Pooling Project, which involved more than 16,000 women ages 20 to 83

from

three centers in the U.S. and one in Shanghai. The studies were only

observational, however. Also, the authors say, the findings may be confounded

by

lifestyle factors they couldn't adjust for.

All of the women had been diagnosed with invasive primary breast cancer.

Their answers on food frequency questionnaires showed that the average daily

soy isoflavone intake among U.S. women was 3.2 mg - significantly lower

than the mean of 45.9 mg in the Chinese women.

During an average follow-up of 9.2 years, 2,622 women had recurrences and

2,592 died.

When the research team compared women in the highest deciles of soy

isoflavone consumption to those in the lowest deciles, they found that higher

soy

food intake after cancer diagnosis reduced the risk of breast cancer

recurrence and all-cause mortality by 15% each.

Using common cutoffs for data from all the cohorts, the investigators found

that women in the highest intake category (> 23 mg/day) had a 9% lower

risk of mortality and a 15% reduced risk for recurrence compared to women in

the lowest category (0.48 mg/day or less).

The research team also found that tamoxifen users with higher isoflavone

intakes had a reduced risk of both all-cause mortality and breast cancer

recurrence, compared with women who did not use tamoxifen and who consumed the

lowest amount of soy food.

The study results cannot be generalized to soy supplements, since they may

differ from soy foods in both the type and amount of isoflavones.

" Ultimately, " Dr. Shu said, " a large randomized controlled clinical trial

is needed to assess the impact of soy food intake on breast cancer

prognosis, and also to assess the role of specific isoflavone supplements in

relation to breast cancer prognosis. "

Reuters Health Information © 2011