Too often we substitute one food for another thinking the later is more healthy and find out just the opposite. Such is the case with soy. Some people replace milk with a soy drink or other dairy products with similar soy products. Others replace animal protein with a soy protein powder shake or possibly with tofu.
Too much soy or improperly processed soy can be attributed to several health problems including thyroid dysfunction and breast cancer. Soy is healthiest in its natural bean state and then fermented. Once it is isolated and made into a powder its properties change enough that consumption can be harmful.
Soy protein isolates are high in mineral-blocking phytates, thyroid-depressing phyto-estrogens and potent enzyme inhibitors that depress growth and cause cancer. Diets in which powdered proteins from soy, (and also egg or milk powders) that are fed to animals or humans cause a negative calcium balance that can lead to osteoporosis.
Soybeans must not be used like other legumes in soups and other dishes but only as fermented products like miso, natto and tempeh. It is also a mistake to rely on tofu or bean curd as a protein food because of its high phytate content. Those who wish to eat tofu would be wise to imitate the Japanese who eat small amounts of tofu in fish broth and not as a substitute for animal foods.
Soy should not be used as a substitute for other foods and moderation would suggest that not more than two helpings of soy a week is wise. For healthy variety, look for fermented soy preparations