Populations that consume the largest amount of soy in their diet have the lowest rates of breast cancer. Researchers attribute soy’s possible protective effect to naturally occurring compounds called isoflavones. When we consume soy foods, bacteria in our intestinal tract convert isoflavones to compounds that have an estrogenlike effect in the body. Acting as weak estrogen compounds, isoflavones are able to attach to estrogen receptors in the body. Genistein and daidzein are the most active soy isoflavones, and have been the focus of much research. Researchers believe that if genistein can bind to estrogen receptors in the breast, they can block the ability of a
woman’s own estrogen from taking that spot. That means that breast cells have less contact with estrogen.
Studies in the laboratory suggest that isoflavones protect from breast cancer. Studies in animals show that supplementing the diet with soy inhibits the growth of breast tumors; studies on human breast cancer cells have found similar effects. But the question remains: does eating soy on a regular basis lower a woman’s risk of breast cancer? No study has been conducted to show what years of eating a high-soy diet does to breast cancer risk. A handful of studies have shown that a regular intake of soy isoflavones may lower circulating levels of estrogen and this might reduce a woman’s future risk of breast cancer. Other studies show that consuming a soy-rich diet can lengthen a woman’s menstrual cycle, thereby influencing how much estrogen your breast cells are exposed to. Based on what we know today, most experts believe women must consume soy foods over their lifetime to realize the potential benefits of soy isoflavones on breast health.
What if you’re at high risk for breast cancer? Or perhaps you’re a survivor of the disease, and you’re leery about eating foods with so-called plant estrogens. The estrogenlike properties of isoflavones have led some experts to be concerned about the use of soy in women with breast cancer because estrogen may increase this risk. Some preliminary studies show that soy has protective effects for breast cancer, while others suggest soy might increase breast cell growth. Because we lack sufficient reliable information about the effect of soy foods on women with breast cancer, a history of breast cancer or a family history of breast cancer, soy should be treated with caution. Until more is known, I advise women in these situations to avoid consuming large amounts of soy each day. I certainly recommend that these women avoid using soy protein powders and isoflavone supplements. But that doesn’t mean you have to give up soy foods. Consuming soy foods three times a week as part of a plant-based diet is considered safe.
If you want to start eating soy foods because they might help reduce your risk of breast cancer, and because they have other health benefits (such as protecting from heart disease), try the following tips to enjoy more soy:
• Try a calcium-fortified soy beverage. Pour it on cereal, add it to soups, use it in baking or enjoy it on its own. Find a product that you like—depending on how they are made, brands can taste very different.
• Snack on roasted soy nuts. These are crunchy, are full of phytoestrogens and have less fat and more fiber than other nuts. Enjoy them as a snack or sprinkle them over your salad. They also come in flavored varieties.
• Cook with canned soybeans. Check out the canned bean aisle of your grocery store for these no-fuss beans. If you can’t find them there, look in the ethnic food section. Add them to chilies, pasta sauces, soups and salads. If you have the time, buy them dried, soak them overnight, then simmer for one hour until they’re cooked.
• Use soy deli meats in place of pepperoni or salami on pizzas and in sandwiches.
• Try soy ground round in your next pasta or burrito recipe.
• Bake with soy flour. You’ll find defatted soy flour at your local health food store. Replace one-quarter to one-half of the all-purpose flour in recipes with soy flour.
• Try cooking with tofu or tempeh. For recipes, information and free brochures on soy foods, visit www.unitedsoybean.org or write to United Soybean Board, 16640 Chesterfield Grove Road, Suite 130, Chesterfield, MO 63005-1429 (Tel: 1-800-989-8721).
• Make a morning power shake with 1 tablespoon (15 ml) of protein powder made from isolated soy protein.