Should You Eat Soy Foods?

Over the past few years, soy seems to have gone from the best food one can eat to the worst. According to soy opponents, tofu causes everything from birth defects to pancreatic cancer. It’s no wonder that people are concerned and confused.

In my opinion, there is a great deal of fear-mongering as well as inaccurate (and one-sided) interpretation of studies. Hundreds of reports in leading peer-reviewed journals worldwide provide compelling research that soy helps to protect against cancer, most notably breast cancer. For example, researchers at Japan’s National Cancer Center followed the eating habits of more than 20,000 women for a decade, and found that those who consumed at least three bowls of miso soup daily reduced their risk of breast cancer by about 40 percent. Miso (a concentrated fermented soybean paste) and all soy foods (as well as many other legumes) are rich in isoflavones, natural compounds that appear to impede the growth of some tumors.

Isoflavones (especially genistein and daidzein) are phytoestrogens, plant compounds that have the ability to interact with estrogen receptors in our bodies. Phytoestrogens are many times weaker than estrogen, but they can either enhance the effects of estrogen if levels are low, or mitigate the harmful influence of estrogen if levels are too high. Because many breast cancers are hormonally driven, phytoestrogens are thought to provide protection. Studies also show that genistein suppresses cell proliferation and stimulates apoptosis, two ways that the body naturally inhibits cancer development.

Soy does more than just protect against breast cancer, though. Studies indicate that it helps to lower harmful LDL cholesterol, protects against osteoporosis, and may reduce the risk of colon cancer by reducing the formation and growth of tumor cells in the gastrointestinal tract.

As you can surmise, I’m a proponent of soy within the context of a healthy, varied diet. I personally enjoy old-fashioned fermented soy products such as tempeh, miso, shoyu and tamari. Soybeans contain “anti-nutrients” such as enzyme inhibitors that can cause digestive problems and interfere with protein digestion, but Asian cultures discovered thousands of years ago that soaking, sprouting, or fermenting the beans neutralizes these anti-nutrients. Eating traditional soy foods in the typical amounts consumed by Asian civilizations for thousands of years does not pose a threat to your health. In fact, I’m convinced that including soy in your diet helps to provide protection against many chronic diseases including cancer, heart disease, and osteoporosis. Of course, if you are allergic or sensitized to soy, you should avoid it.

Tofu and soy milk are more processed than fermented soy foods, but they are also traditional foods with a long history of use and are fine enjoyed occasionally. Edamame (green immature soybeans) contain fewer of the toxins found in the mature beans and can also be eaten occasionally.

However—and this is important—you should avoid soy products that are refined or made from genetically engineered beans. Soy protein isolate, soy protein concentrate, texturized vegetable protein and hydrolyzed vegetable protein are highly processed modern creations found in shake powders, energy bars and veggie burgers. I also advise against consuming soy oil, which is typically subjected to heavy refining and deodorizing to make it bland enough to be acceptable. The worst soy oil products are margarines and shortenings made from partially hydrogenated soybean oil, which contains dangerous trans-fatty acids.

Bottom line: Enjoy traditional soy foods in moderation. I recommend 3-4 servings per week. This is about how much I eat each week, usually in the form of tempeh or tofu. My favorite way of eating tofu is to marinate it and make a wrap sandwich with some veggies and homemade plum sauce. It is delicious! In terms of daily consumption of soy isoflavones, most people should average between 20-50 grams. (A 3-ounce serving of tempeh contains about 37 grams isoflavones, 3-ounces of tofu contains 20, and ¼ cup of miso paste contains 29.)  This amount appears to mimic what traditional cultures consume and is also the amount confirmed in studies to offer numerous health benefits.

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