Soy and soybeans are a popular, albeit controversial, source of protein. Unlike many other “beans” or legumes, soybeans are a complete source of protein. Eating soy in the most whole form is the best way to get protein. Also, fermented forms of soybeans such as tofu and natto are excellent sources of protein and offer more health benefits than soybeans. There is about 23 grams of protein in an ounce of whole soybeans.