Though the word "protein" usually conjures up images of meat, fruits and vegetables can also be good sources of protein; they are lower in saturated fat and higher in dietary fiber than animal sources and when regularly eaten can help lower cholesterol and reduce the risk of heart disease, diabetes and certain cancers, according to the American Heart Association. Plant proteins, unlike animal proteins, only contain some of the nine essential amino acids that we cannot make ourselves, so they must be combined with other protein foods in order to ensure adequate intake.
Soybeans are the No. 1 source of vegetable protein, and are a complete protein, meaning they contain all of the essential amino acids. Each cup of cooked soybeans offers 29 g protein. Soy products such as tofu have less protein, coming in with 11 grams in every 4 oz. serving.
Beans pack a punch of protein. White beans and lentils contain about 19 g protein per cup, providing many essential amino acids such as isoleucine and lysine. Black beans contain 15.2 g per cup, while kidney, lima, black-eyed, navy and pinto beans contain about 14 g per cup.
Broccoli is another vegetable that contains an abundant amount of protein. Its protein content is 34 percent of its dry matter, offering 4.6 g of protein per cup of cooked broccoli. Cauliflower, a cousin of broccoli, is not too far behind at 27 percent, or about 3 g per cup.
Known for its excellent nutrient profile, spinach is also a good source of protein. Cooked spinach contains 5.3 g of protein per cup, while frozen or canned, drained spinach contains slightly more at 6 g per cup.
Corn, artichokes, and potatoes are other vegetables that contain a decent amount of protein. Corn provides about 5 g per cup. Artichokes might take a while to cook, but are worth it -- a medium artichoke contains about 4.2 g of protein per cup. A potato with its skin provides about 5 g of protein; removing the skin drops its protein content by 2 grams. Sweet potatoes have about 3 g of protein per potato.
Fruits, on the whole, contain less protein than vegetables and legumes. Cantaloupe’s protein content is 11 percent of its dry matter, which is about one-third of the amount of protein in some vegetables. Fresh strawberries are 7.5 percent protein, while navel oranges contain 7.2 percent protein. Watermelons and bananas are 6.4 and 5.1 percent protein, respectively. Other fruits contain less than 5 percent protein.