A. Yes. There's very little research examining the use or consumption of soy in women with breast cancer. But we do know that soy contains phytoestrogens, plant-based compounds that have an estrogen-like effect in the body.
Since estrogen may stimulate the growth of breast cancer—particularly the estrogen-receptor-positive (ER+) form of the disease—soy products may have an effect on the remaining breast tissue. The concern is that it could activate dormant cancer cells, causing them to spread to other organs.
Based on this theory, most oncologists recommend that patients avoid estrogenic substances in any form, including soy foods and soy-based beauty products. It's tough to advise patients when there's minimal data on the topic, so experts tend to take a conservative approach to play it safe.
Kevin P. Hubbard, D.O., is a professor and chair of the department of internal medicine at the Kansas City University of Medicine and Biosciences College of Osteopathic Medicine
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