Fermented Soy Products: Miso, Tempeh, and Soy Sauce
Miso (a soybean paste used for seasoning and in soup), tempeh (a chewy cake made from whole cooked soybeans), and soy sauce are all traditional, fermented soy products. When you hear claims about all the soy eaten in Asian cultures and how it contributes to good health, these are the foods behind it all. The fermentation process negates the effect of the phytic acid in soy--which blocks zinc and other minerals from being absorbed by the body--and creates probiotics that aid in digestion. In addition, many studies have shown that these foods may prevent heart disease and certain cancers.
Verdict: The gold standard. Miso, tempeh, and soy sauce can be consumed without worry.
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While tofu, made from unfermented cooked pureed soybeans, has gained a reputation over the years as a health food and the perfect substitute for meat, critics warn that eating too much of it can lead to mineral deficiencies and improper digestion.
Verdict: Eat tofu in moderation. Large slabs of it every day may not be wise.
Soy milk, a distinctly Western product, is made by grinding dehulled soybeans and mixing them with water to form a "milk." But along the way in this process, the soy is treated with heat, alkalines, and acids that ultimately compromise the quality of its proteins and vitamins. Drinking soy milk regularly also means you're taking in a lot of the phytoestrogens that are present in soy, which, some studies show, can interfere with normal hormonal activity in our bodies. There are other studies, however, that dispute this. And many will argue that soy milk is a healthy alternative for people who are lactose-intolerant.
Verdict: Hung jury. There is so much contradictory evidence that it's tough to make a blanket recommendation. If you have concerns about soy milk, you can try rice milk or nut milks, and make a point of getting some of your calcium from greens and whole grains instead.
Textured soy protein, also known as TSP or TVP, is a processed product that has a texture similar to ground beef or stew meat. Often used in school lunch foods (remember those school hamburgers that somehow didn't taste like normal hamburgers?) and canned or frozen meatless "meats," TSP tends to have numerous artificial flavorings added to it in order to make it taste, well, meaty.
Verdict: You're better off eating more whole, less processed forms of soy.
Soy Isoflavone Supplements
Available over the counter in pill or powder form, the soy isoflavones daidzein and genistein (both are phytoestrogens) are often promoted as supplements to help lessen menopausal symptoms like hot flashes. While there are some studies that show these chemicals may help prevent breast cancer, there are other studies that show the complete opposite--that they actually can increase the risk of breast cancer.
Verdict: Stay away from these. Especially since the evidence that they soothe hot flashes is weak anyway.