Corn does have all of the essential amino acids but is considered a "low-quality" protein or what used to be called an "incomplete" protein. Low-quality protein foods may be lacking or have very low quantities of the nine essential amino acids and, therefore, should be combined with other foods to provide adequate amounts of all essential amino acids. All protein is comprised of amino acids, and essential amino acids cannot be made by the body, meaning they must be provided through your diet. The nine essential amino acids are: histidine, isoleucine, leucine, lycine, methionine, phenylalanine, threonine, tryptophan and valine.
High-Quality Protein Combinations
Many plant based foods are considered low-quality proteins compared with animal-based proteins, which are generally higher in the essential amino acids. If you eat a plant-rich or vegetarian diet, you can still meet all of your essential amino acid needs by combining various foods throughout the day. Corn and beans, nuts like peanut butter on whole-wheat bread, rice and beans or soy-based foods like tofu, tempeh or veggie burgers are a few options of lower-quality proteins that when combined provide all of the essential amino acids.