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.
While much of the protein in the American diet comes from beef and pork, this isn't necessarily the case around the world. People in some countries eat little or no meat, getting much of their protein from vegetarian protein sources, and some people get their protein from foods many Americans have never tried.
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.