Soybeans are a high-protein legume, or bean, grown as food for both humans and livestock. The word soy is derived from the Japanese word shoyu (soy sauce/soya sauce). The soy plant has the highest-quality protein of any plant food, and its high level of protein content is considered equivalent to animal foods. Soy is considered to be a complete protein, like meats, meaning that it provides all the essential amino acids your body needs but doesn’t produce on its own.