Glutamine
Glutamine is the most abundant naturally occurring, nonessential amino acid in the human body, and one of the few amino acids that can directly cross the blood–brain barrier. Humans obtain glutamine through catabolism of proteins in foods they eat. In states where tissue is being built or repaired, like growth of babies, or healing from wounds or severe illness, glutamine becomes conditionally essential.
Essential amino acid
Although plants tend to have less protein per weight than animal sources such as eggs or milk, they are nevertheless "complete" in that, as a whole, they contain all of the amino acids essential in human nutrition. The same is true for algae and marine phytoplankton. Eating various plant foods over an extended period of time can provide a protein of higher biological value. Certain native combinations of foods, such as corn and beans, soybeans and rice, or red beans and rice, contain the essential amino acids necessary for humans in adequate amounts. However, the idea that plant-based foods must be combined to provide humans all of the essential amino acids is outdated. The official position of the Academy of Nutrition and Dietetics is that protein from a variety of plant foods eaten during the course of a day supplies enough of all essential amino acids when caloric requirements are met.