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. Sources of protein include grains, legumes and nuts, as well as animal sources such as meats, dairy products, fish and eggs.