Beans, the large edible seeds of the plant family Fabaceae, contain a high amount of protein. Soybeans have the highest protein content of any bean. One cup of cooked soybeans, equal to one serving, contains 28.5 grams of protein, almost half of the recommended amount in a 2,000 calorie diet.
The protein content of beans does lack several key amino acids necessary for proper nutrition. These amino acids can be found in other plant-based protein sources, such as nuts, brown rice, other whole grains, dairy products and meat products. Beans have been cultivated by humans throughout the world for thousands of years.