A complete protein is one that contains all essential amino acids. The human body contains 21 amino acids. Of those, nine are essential. Essential amino acids cannot be manufactured by the body and must be obtained through diet. Amino acids play a number of important roles in the body and must be consumed on a regular basis in order to stay healthy. A varied, well-balanced diet is essential to ensure that you're getting all of the amino acids your body needs.
Essential Amino Acids
The nine essential amino acids are leucine, lysine, isoleucine, phenylalanine, methionine, tryptophan, threonine and valine. Children also need arginine, cysteine and tyrosine, as their bodies cannot produce enough while they're developing.
Vegans might have a harder time meeting their amino acid needs if they don't consume a varied diet. According to Vegan Outreach, vegans should focus on getting enough lysine in their diets. Vegan foods contain small amounts of lysine but larger amounts of other essential amino acids. If you focus on getting enough lysine to meet your needs, you're likely to also all of the other essential amino acids. This is because foods that contain enough lysine contain even more of the other amino acids. Legumes, including tofu and tempeh, contain the highest amount of lysine. Pistachios and quinoa are also sources. Vegans can also try spirulina.
Sources of Amino Acids
The best sources of essential amino acids are animal products. Vegetarians who eat eggs and dairy products should have no problem getting enough complete protein into their diets. Almost all sources of proteins, vegetarian or not, contain most of the amino acids. However, some contain small amounts of one and high amounts of others, so it's important to eat a variety of foods to get complete proteins in your body.
Despite the common belief that you must "combine foods to create a complete protein," this is not true. You do need to eat a variety of vegetarian foods to get all of the essential amino acids. However, you don't have to eat these foods at the same time or in specific quantities. If you eat grains and legumes on a daily basis, you'll be eating a complete protein. Some foods do work well together, so you might want to try the combination. For example, rice and beans together are a complete protein.