The flip side is that soy isoflavones can disrupt the delicate hormonal balance in the body, leading to problems involving the thyroid, irregular menstrual cycles and infertility. A glass of soymilk has about 35-40mg of isoflavones. A half-cup serving of tofu, miso, tempeh or soybeans has about 40mg of isoflavones, also. Fermented foods like tempeh and miso may be less of a problem, but more research would need to confirm this. Soy hot dogs or cheese have lower amounts of isoflavones because of processing.
Soy sauce has almost none.
Soy infant formula should not have any isoflavones, but this is usually not the case. There has been no upper limit set as to the amount of soy that is beneficial, or just how much is too much. Some research has used amounts as high as 200mg of soy isoflavones to show its benefits against cancer. Other research has shown that anywhere from 27 to 50 mg daily of isoflavones lowers total cholesterol and improves HDL levels. In Japan, there is no word for menopause because presumably women do not suffer the usual symptoms.