("If I give my son soy products, will he develop breasts?" or "If I give my daughter soy milk, will she get her period at 9?" are not uncommon questions.) Soy comes from soybeans. It has the highest protein content of any vegetable and is the basis of a number of different food products including tofu, soy sauce, and soybean oils. Phytoestrogens are a natural component of soy.

Estrogen is a hormone produced by the human body. Hormones are a type of steroid. Steroids are a class of chemicals that share the same general chemical structure; they can be naturally occurring (like testosterone and cholesterol) or they can be manufactured drugs (like prednisone or anabolic steroids). What steroids share in common is their general chemical backbone; their specific effects on different organs and tissues vary dramatically.

While phytoestrogens look chemically similar to estrogens, they do not behave like them in the body. This is because phytoestrogens are NOT steroids. Therefore, they do not affect organs and tissues in the body (like breast tissue) the same way estrogen does. Furthermore, when a person eats a soy product, it is cleared from the body in a single day. Compare this to synthetic estrogen, which is a true steroid; these chemicals are often stored in the body for years. Even though phytoestrogens look chemically similar to estrogens, they do not behave similarly in the body.

There's a lot of disagreement over whether phytoestrogens are beneficial or dangerous. Some researchers have published studies showing that soy and its components are protective against heart disease and breast cancer, especially when exposure occurs during childhood. Other studies suggest that phytoestrogens have adverse effects on reproductive function, immune function, and the thyroid gland. Some studies even suggest that they can ultimately lead to certain types of cancer.

Find out what else Dr. Cara Natterson has to say, including whether or not you should feed your kids soy.

Dr. Cara Natterson, author of Your Toddler: Head To Toe, is a pediatrician and mother of 2. To buy a copy of her book, click here. She is currently working on the forthcoming book entitled Dangerous or Safe?

Read more from Dr. Cara.