Quinoa is pseudo-grain with complete protein. The presence of complete proteins in a plant-based food source is unusual. Soybean is the only other plant source with complete protein. Complete protein is also called quality protein. A protein with all of the 8 essential amino acids is called complete protein. Proteins that do not have all of the 8 essential amino acids are called incomplete proteins.
Essential Amino Acid
The amino acids that the body cannot produce are called essential amino acids. Essential amino acids must be introduced exogenously for the body to maintain normal functional integrity. All of the essential amino acids are present in quinoa in proper and adequate amounts and proportions for utilization by the human body. The essential amino acid composition of quinoa is phenylalanine, lysine, valine, threonine, tryptophan, isoleucine, methionine and leucine. Some amino acids such as l-arginine are not produced in enough quantities by the body. These amino acids are called semi-essential amino acids. Some people group the semi-essential amino acids with the essential amino acids. Consequently, some references would show that there are 9 essential amino acids.
Incomplete Protein
Lysine and tryptophan are the two essential amino acids that are often missing or are found in small amounts in the plant-based sources of protein. The absence or low levels of these amino acids make them the limiting essential amino acids. A limiting amino acid is an amino acid in low concentration, making it the determinant of the rate of protein synthesis. Lysine is a limiting amino acid in corn, wheat and rice, whereas, tryptophan is the limiting amino acid in legumes.
Body Building
The type of proteins consumed has important implications for body building. Protein synthesis cannot be completed if an essential amino acid in the protein chain is missing. The part of the protein chain being synthesized would then be broken down and its amino acids used for energy metabolism. Body building and repair of damaged tissues is more effective if complete protein is consumed. Therefore, quinoa is more effective for body building compared to kidney beans, lima beans and other legumes.
Proteins for Vegetarians
The sources of protein is an important point of concern for vegetarians. Animal sources are replete with complete proteins, whereas, quality proteins are rare from plant sources. Vegetarians usually consume foods from a variety of plant-based sources to meet the body's need for proteins. Quinoa makes it easier to maintain adequate nutrition without consuming foods from a variety of sources.
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