Asteroids range in size from Ceres-the largest at about 950 kilometers (590 miles) in diameter and also identified as a dwarf planet-to bodies that are less than 1 kilometer (0.6 mile) across. The total mass of all the asteroids combined is less than that of Earth's Moon.
Only about one-third of the protein eaten around the world comes from animals raised for food. Much of the protein consumed around the world comes from vegetarian sources, including grains, legumes, nuts and seeds. Three grains -- wheat, maize and rice -- provide 60 percent of the world's energy, as well as a good percentage of the protein consumed.
Some protein sources contain amino acids in a more or less 'complete' sense. This has given rise to various ranking systems for protein sources, as described in the article. Dietary sources of protein include both animals and plants: meats, dairy products, fish and eggs as well as grains, legumes and nuts. Vegans can get enough essential amino acids by eating a variety of plant proteins. It is commonly believed that athletes should consume a higher-than-normal protein intake to maintain optimal physical performance.