Soybeans contain genistein, a weak estrogen that may help to prevent breast cancer. They contain omega-3 fatty acids that help prevent heart attacks, and are loaded with fiber that helps to prevent diabetes. But soybeans contain trypsin inhibitors that block protein consumption and hemagglutinin that causes clots to form. It you take in huge amounts of soybeans, you increase your risk for pancreatic damage and even pancreatic cancer because the trypsin inhibitors block protein use and therefore make your pancreas work too hard to overcome this effect. Huge amounts of soybeans can also make clots that can form in your heart or lungs.
Soy contains goitrogens that block thyroid function.
In small doses these goitrogens do not harm you, but large doses can slow your thyroid. Dr. Enig is particularly concerned about the widespread use of infant formula made from soybeans. We have no data yet on the consequences of feeding plant estrogens to small children. If you choose to use feed you baby soy milk, cow's milk or any formula other than breast milk, I recommend that you introduce other foods as early as possible to add variety to the diet and reduce your infant's reliance on any single food. When you hear about the health benefits of any food, don't believe that you should start eating it to the exclusion of other foods.