Soy is obtained from the one-year soybean plant and is a member of the legume family. The history of its use in human nutrition goes back to about 5000 years ago. Maybe if you talk to the mummies, they will say that they used soybeans for their cooking!
Soy protein is known as the best and highest quality vegetable protein in the world and contains 9 essential amino acids needed by the body throughout the day, but in general, compared to animal proteins, it is not a complete protein.
