The soybean has been a part of the human diet for almost 5,000 years. Unlike most plant foods, the soybean is high in protein and is considered equivalent to animal foods in terms of the quality of the protein it contains.

Soy in your diet can lower cholesterol. There are many scientific studies that support this conclusion. In fact, the Food and Drug Administration (FDA) agreed that 25 grams per day of soy protein, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease.

Other potential benefits include:

• fewer menopausal symptoms
• reduced risk of osteoporosis
• possible prevention of hormone-dependent diseases, including breast cancer, endometrial cancer, and prostate cancer

If you look on the shelves of your health food store or supermarket in search of soy protein products, you'll see everything from veggie burgers to food bars to powdered soy protein beverages. However, not all soy protein products contain the same amount of protein. The following list ranks some popular products from greatest amount of soy protein to lowest:

• Soy protein isolate (added to many soy food products, such as soy sausage patties or soybean burgers)
• Soy flour
• Whole soybeans
• Tofu

The best way to find out about protein content is to look on the product's Nutrition Facts label to see the percentage of soy protein. Also look at the list of ingredients: if a product contains isolated soy protein (or soy protein isolate), the protein content should be fairly high. When the FDA-approved health claim is made, the label will also indicate how many grams of soy protein are in one serving of that product.

Note: There's a difference between soy supplements (commonly sold in tablets or capsules) and soy protein products. Soy supplements are generally composed of concentrated soy isoflavones. While soy isoflavones may be helpful in treating symptoms of menopause (isoflavones behave similarly to estrogen), there is not enough evidence to support using soy isoflavones for any of the other health benefits mentioned above, like lowering cholesterol.

For individuals who are not allergic to soy, no serious short-term or long-term side effects have been reported from eating soy foods. Common mild side effects include stomach upset and digestive problems, including constipation and diarrhea.

In adults, 25 grams per day of soy protein may reduce the risk of heart disease.

Soy foods and soy-based infant formula are widely used in children, but there are no studies that have determined whether isolated soy protein or isoflavone supplements are useful or safe in this population. Therefore, isolated soy products are not recommended for use with children at this time.