High soy intake linked to reduced breast cancer mortality
MedWire News: Researchers have found that Chinese women with breast cancer and a higher intake of soy food have a lower risk for breast cancer recurrence and death, than those with low intakes.
“Soy foods are rich in isoflavones, a major group of phytoestrogens that have been hypothesized to reduce the risk for breast cancer,” explain Xiao Ou Shu (Vanderbilt University Medical Center, Nashville, Tennessee, USA) and colleagues.
“However, the estrogen-like effect of isoflavones and the potential interaction between isoflavones and tamoxifen have led to concern about soy food consumption among breast cancer patients,” they add.
In the present study, Shu and team examined the association between soy food intake and breast cancer recurrence and survival in a population-based study of 5033 female breast cancer survivors in China.
The researchers report that during a median follow-up of 3.9 years there were 444 total deaths and 534 recurrences or breast cancer-related deaths.
Soy food intake, as measured by either soy protein or soy isoflavone intake, was inversely associated with mortality and recurrence. Women in the highest quartile of soy intake had a 29% reduced risk for total mortality and 32% reduced risk for recurrence compared with women in the lowest quartile of intake.
The adjusted 4-year mortality rates were 10.3% and 7.4% for women in the lowest and highest quartiles of soy protein intake, respectively, with corresponding 4-year recurrence rates of 11.2% and 8.0%.
The inverse association did not appear to vary by menopausal status and was evident for women with estrogen receptor (ER)-positive and ER-negative cancers, early and late-stage cancers and in tamoxifen users and non-users.
“The association of soy food intake with mortality and recurrence appears to follow a linear dose-response pattern until soy food intake reached 11 g/day of soy protein; no additional benefits on mortality and recurrence were observed with higher intakes of soy food,” write Shu and co-authors in the Journal of the American Medical Association.
They conclude: “This study suggests that moderate soy food intake is safe and potentially beneficial for women with breast cancer.”
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By Laura Dean