Soy Linked to Reduced Mortality Risk for Certain Breast Cancer Survivors
Findings in a recent study suggested that the high consumption of isoflavone, the main phytoestrogen found in soy, was associated with reduced all-cause mortality risk in certain breast cancer survivors.1
Conflicting evidence from various studies has suggested that isoflavone may both slow the growth of cancer but also reduce the effectiveness of endocrine therapies used to treat breast cancer. Currently, there is no consensus on how much or how little soy products breast cancer patients should consume.
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In their study, researchers examined the association between dietary intake of isoflavone and all-cause mortality in 6235 women with breast cancer enrolled in the Breast Cancer Family Registry, and followed-up with participants for approximately 9.4 years. Researchers assessed dietary intake using the Food Frequency Questionnaire developed for the Hawaii-Los Angeles Multiethnic Cohort among 5178 women who reported on their prediagnosis diet and 1664 women who reported on their postdiagnosis diet.
Over the course of the study, a total of 1224 deaths occurred.
Researchers observed a 21% decrease in all-cause mortality in women who consumed the largest amount of isoflavone compared with women who consumed the least amount of isoflavone (≥1.5 vs < 0.3 mg daily: HR, 0.79; 95% confidence interval [CI], 0.64-0.97; Ptrend = .01). In addition, lower mortality associated with higher intake of isoflavone was limited to women with tumors that were negative for hormone receptors (HR, 0.49; 95% CI, 0.29-0.83;Ptrend = .005) and women who did not receive hormone therapy (HR, 0.68; 95% CI, 0.51-0.91; Ptrend = .02). However, the interactions did not reach statistical significance.
“At the population level, we see an association between isoflavone consumption and reduced risk of death in certain groups of women with breast cancer. Our results suggest, in specific circumstances, there may be a potential benefit to eating more soy foods as part of an overall healthy diet and lifestyle,” said lead author Dr Fang Fang Zhang of the Friedman School of Nutrition Science and Policy at Tufts University.2
—Melissa Weiss
Reference:
1] Zhang FF, Haslam De, Terry MB, et al. Dietary isoflavone intake and all-cause mortality in breast cancer survivors: The Breast Cancer Family Registry [published online March 6, 2017]. Cancer. doi:10.1002/cncr.30615.
2] Isoflavones in food associated with reduced mortality for women with some breast cancers [press release]. Boston, MA: Tufts University; March 6, 2017. http://now.tufts.edu/news-releases/isoflavones-food-associated-reduced-mortality-women-some-breast-cancers.