Breast cancer patients advised to avoid soy. (Phytoestrogens at Issue).
Epidemiologic evidence clearly demonstrates a significantly lower risk for breast cancer among women whose diets routinely contain soy products, but recent investigations have suggested that the phytoestrogens in soy may stimulate tumor cells already established in breast tissue, Mindy S. Kurzer, Ph.D., said at a conference on complementary and alternative therapies for cancer.
"At this point, in my view, the concern is theoretical. There have been no studies that have connected soy or isoflavone consumption with cancer in women," she added.
In vitro and animal studies have identified pro- and antiestrogenic effects for the isoflavone phytoestrogens such as genistein that are present in soy. These flavonoids also inhibit cell cycle progression, DNA synthesis, and angiogenesis, said Dr. Kurzer of the department of food science and nutrition at the University of Minnesota in St. Paul. Soy is seen as a possible cancer-preventing product, consumed either as food or in supplements.
But in one study ingestion of a soy protein isolate for 1 year led to stimulation of nipple aspirate fluid volume in premenopausal women (Cancer Epidemiol. Biomarkers Prey. 5:785-94, 1996). In a second study 2 weeks of soy supplementation resulted in increased breast secretion of pS2 and decreased levels of apolipoprotein D in nipple aspirates (J. Clin. Endocrinol. Metab. 84:4017-24, 1999). These findings reflect weak estrogenic effects on the breast, Dr. Kurzer said at the conference, sponsored by the Center for Mind-Body Medicine and the University of Texas, Houston.
Women who have no history of breast cancer and wish to add soy to their diets should consume amounts in the range of typical Asian diets--from one to two servings per day "This is unlikely to be harmful even in women at high risk" for breast cancer, Dr. Kurzer said. But, in general, phytoestrogen pills should be avoided "because we know very little about their actions."
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|Publication:||OB GYN News|
|Date:||Dec 15, 2001|
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