Does this sound familiar? About twenty years ago I was told that soy was a health food. I heard about how Japanese women rarely got breast cancer, and that ingredients called isoflavones in all the tofu they ate and miso soup they slurped protected them from it. So I loaded up on soy burgers, edamame, soy-packed energy bars—I even remember making low-carb muffins once using soy flour (as I'm sure I don't have to tell you, they tasted like sofa cushion stuffing).
But a few years later I started to hear that maybe soy wasn't such a good idea—health authorities were saying that maybe too much of it could cause breast cancer, since those isoflavones that they'd thought were so great are chemically similar to estrogen, and many breast tumors (and some reproductive and lung tumors too) are fed by estrogen. So I cut back on the soy. Then more recently alternative medicine authorities have been abuzz with the claim that soy is positively poisonous—they blame it for ailments including hypothyroidism, breast cancer, brain damage, and that's just the beginning. Concerned, I pretty much eliminated soy unless it's part of a well-rounded meal at a Thai or Japanese restaurant.
Despite the widespread fear of soy, mainstream doctors and nutritionists still seem to consider it a "health" food. Just today I found an article in my local paper in which a Stanford professor calls tofu one of the healthiest foods you can eat, and cites a Chinese study in which women who ate more of it had a reduced risk of breast cancer.
Luckily, this Huffington Post article by Dr. Mark Hyman clears up a lot of the confusion. He examines a long list of studies on soy, which seems to show that soy isn't the poison that many would have you believe, and that there's some evidence that it's beneficial. For example, post menopausal women who consume isoflavones have decreased breast density (a good thing, since denser breast are associated with cancer).
But you must know that there seems to be a crucial difference between fermented soy products (tofu, miso, tempeh) and non-fermented soy, which includes most of the processed soy protein found in soy milk, energy bars, soy burgers and many packaged foods that you didn't even realize contained soy. Asian cultures have been consuming fermented soy for centuries, but "soy protein isolate" and its cousins are a modern phenomenon that we still don't know much about (and are creepily omnipresent on ingredient lists). Just one reason to avoid them: A recent report by the Cornucopia Institute revealed that something like 99% of the soy protein found in non-organic veggie burgers, energy bars and similar products is extracted from the soybeans using a toxic petrochemical called hexane—gross, and troubling that big name brands that you probably think of as ultra-healthy are using such a dodgy ingredient.