Various types of protein
Proteins are made up of small aggregates of amino acids. According to the FDA, there are as many as 20 types of amino acids, which can be broadly divided into two groups. Nine of the 20 are called "essential amino acids" and cannot be produced by our body, so they need to be taken from food. The remaining 11 types are called "non-essential amino acids" and are produced by the body in the process of decomposing essential amino acids or proteins. In addition, it is considered to be a "conditionally essential amino acid" because it is essential in a serious situation where the body does not synthesize amino acids normally.
Foods with all nine essential amino acids are called "complete protein". Animal foods and soybeans fall under this “complete protein”, but “vegetable foods” lack essential amino acids and are therefore classified as “incomplete protein”.
So, isn't it true that people such as vegetarians and vegans can't get essential amino acids? All essential amino acids can be easily obtained by eating various variations of incomplete protein.
Most of the incomplete proteins lack one or two kinds of amino acids, and most of them can be supplemented by others. For example, grains are low in the amino acid lysine, and beans and nuts are low in the amino acid methionine. But if you eat a combination of beans and rice, or a whole grain bread with nut butter, you can get all the same amino acids as you would eat chicken. The National Library of Medicine recommends eating various incomplete proteins throughout the day to supplement each other.