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New Research Shows Soy May Prevent Breast Cancer (dateline February 1, 2000)

A preliminary study funded by the United States Department of Agriculture revealed that diets containing soy protein help protect against breast cancer. The study, conducted at the Arkansas Children’s Nutrition Center, found that a soy protein diet prevented approximately 25% of breast cancers that had been chemically induced in test rats. Though the study must be confirmed by additional research, U.S. Agriculture Secretary Dan Glickman said that the study is significant and stresses the link between nutrition and health.

Researchers believe that soy works against cancer similarly to the drug tamoxifen, which is currently the most commonly prescribed drug to treat and prevent breast cancer. Soy, like tamoxifen, blocks the hormone estrogen from binding to estrogen receptors in breast cancer cells. Since some breast cancer cells depend on estrogen for survival, a lack of estrogen starves these cells, causing them to die. Previous studies on soy have suggested that diets rich in soy protein may help block breast cancer at an earlystage, when estrogen receptors are presumably still in function.

In a study conducted by Jane Lu of the University of Texas Medical Branch in Galeston, women who consumed soy milk every day between one and five months reduced the amount of estrogen in their blood by 30% to 40%. Lu concluded that soy protein diets may be useful for preventing breast cancer since decreasing estrogen levels will in turn slow reproduction of cancer cells. Lu also noted that there is a much lower incidence of breast cancer among Asian women who tend to eat more soy products than American women.

Nutritionists warn that while including soy in the diet may be helpful, very large quantities of soy (over 100 mg per day) may flood estrogen receptors. Since post-menopausal women and children do not have large amounts of estrogen in their bodies, they should be particularly aware of their soy intake. The average amount of soy recommended for women to help protect against breast cancer is 35 grams per day—also the average amount Asian women consume per day. 60 grams is the maximum amount of soy used in clinical trials involving breast cancer patients.

There are a variety of soy products available on the market. These include: soybeans, soy burgers, soy hot dogs, soy chicken, roasted soy nuts, soy milk, soy bacon, tofu, tempeh, bean paste, and soy parmesan. Powder-based soy that may be added to fruit, water, and ice to make shakes are available in most health food stores. Unflavored soy powders may be added to a variety of liquids including lemonade, fruit smoothies, or soups.

Though further research on the specific benefits of soy is needed, researchers have known for years that a diet rich in fruits and vegetables can help prevent breast cancer as well as gastrointestinal and respiratory tract cancers. Monounsaturated fats, such as canola oil or olive oil, have been linked to lower breast cancer risk while diets high in polyunsaturated fats such as corn oils, tub margarine, and saturated fats in meats have been associated with a higher risk of breast cancer.

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