Legumes are a type of edible seed pod that splits into two halves. Types of legumes include beans, lentils and peanuts. Versatile and nutritious, legumes provide fiber, folate, potassium and iron. Legumes are also recommended as a healthy alternative to animal-derived foods because of their high-protein content. All legumes are considered good sources of plant-based protein, although there are some variations among legumes with regard to which amino acids and how much overall protein they provide.
Beans are one type of legume. They don't provide all of the essential amino acids and are therefore considered an "incomplete" source of protein. Although this was considered a potential problem decades ago, now it's understood that eating a normal varied diet will easily help you meet all of your amino-acid requirements. In other words, the fact that beans are an "incomplete" source of protein doesn't make them any less beneficial than "complete" sources. Different beans provide different amounts of protein. Adzuki beans, a small red bean used in Japanese dishes, contain 17 g of protein in one cooked cup. A cup of black beans contains 15 g of protein; a cup of kidney beans contains 13 g of protein; and a cup of chickpeas contains 12 g of protein.
Lentils are another type of legume. These small, lens-shaped legumes can be eaten as a side dish or added to stews and soups. Like beans, lentils don't contain all of the essential amino acids, although they are still considered an excellent source of protein if you eat a varied diet. One cup of cooked lentils contains 18 g of protein.
Peanuts -- despite their name and many people's belief that they are a nut -- are actually a type of legume. One cup of raw Virginia peanuts contains 36 g of protein.
Peas also fall into the legume category. Peas are available whole and split and can be eaten as a side dish or added to soups. One cup of cooked whole green peas contains 8 g of protein. One cup of cooked split peas contains 16 g of protein.
Unlike other legumes, soybeans contain all of the essential amino acids, making it a complete source of protein. One cup of cooked mature soybeans contains 28 g of protein. One cup of green soybeans, also known as edamame, contains 22 g of protein. Soybeans can be made into tofu, commonly used as a meat substitute in vegetarian dishes. A 1-cup serving of tofu contains 40 g of protein.