Complete and Incomplete Proteins

Of the twenty amino acids that play a significant role in the human body, eight or ten are an essential part of diet (the rest can be made by changing other amino acids). It is also necessary that there should be enough of each one, and that all should be eaten at the same meal, so that the body can have the full range to work on. This means that proteins which contain all the essential amino acids in the proportions in which they are needed are more valuable as foods than those which lack or do not have enough of a vital component. Foods of animal origin are, as might be expected, the most valuable. They are said to provide ‘complete’ proteins—though in fact this is an exaggeration, as is shown in the table.