Combining two incomplete protein sources in one meal to provide a significant amount of all essential amino acids is called protein combining. For example, grains are lower in lysine and legumes are lower in methionine. Eating grains and legumes together will provide a considerable amount of all essential amino acids.
This concept originated in the early 1970s to ensure vegetarians were getting all the essential amino acids needed for good health.
Protein combining can be a very complicated process and we now know that it is not necessary. Whatever amino acid one food lacks can come from other foods you eat throughout the day. Obtaining the full spectrum of essential amino acids can easily be done through variety.
Research indicates that eating an assortment of minimally or unprocessed foods throughout the day will provide all essential amino acids needed for a healthy adult.
Protein, along with fat and carbohydrates, is essential to human health. We often think of protein as a single nutrient but it is actually made up of amino acids, each with a slightly different structure.
Certain amino acids can actually be made by our body and are referred to as nonessential amino acids. The remaining nine amino acids are considered essential. Our bodies cannot make these amino acids so they must be provided through food.
Essential Amino Acids:
Consuming all essential amino acids is necessary for optimal health. Animal sources of protein, such as eggs, dairy, meat, fish, and poultry contain a high amount of all essential amino acids. For this reason they are called a complete and high source of protein. Plant sources of protein, such as legumes, nuts, seeds, and vegetables tend to be low in one or two essential amino acids. For this reason they are called incomplete sources of protein.
As long as you consume all types of amino acids throughout the day, you are in good shape. Combining proteins in one meal is not necessary even though it was and is popular for many dieters.