The soybean industry has generated so much publicity on the health benefits of soybeans that some people eat soy products at every meal. That's a mistake, because too much of anything can be harmful.

Virtually all plants contain some chemicals that make us healthy and some chemicals that can harm us. Fortunately for us, our ancestors picked out plants that contain more good chemicals and therefore are healthful, and taught us to avoid those that are poisonous. However, if you eat large amounts of one food, you can poison yourself, even though reasonable amounts are harmless or beneficial.

Soybeans are a good example. 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 could 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 could slow your thyroid. Soybeans (and many other plants) also contain phytates, which can block the absorption of minerals. Nobody has shown that phytates in soybeans are harmful; this is a theoretical concern.

Some researchers are 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 abnormally large amounts of that food, or eating one food to the exclusion of other foods. Huge amounts of any single food can be harmful. A healthy diet contains a WIDE variety of fruits, vegetables, whole grains, beans, nuts and other seeds; and modest amounts of any other foods that you enjoy.