Protein Like carbohydrate, protein provides calories that can be used by the body as a source of energy, but there are many vital functions that only protein can perform. For instance, proteins are part of enzymes, which are compounds that facilitate and accelerate chemical reactions throughout the body. Proteins also serve as building materials for the growth and repair of body tissues. The basic building blocks of protein are called amino acids. Your body can produce 11 of them, but nine of them are essential, meaning they must be supplied by the diet.
Complete proteins contain ample amounts of all essential amino acids.
But don't be fooled by the word incomplete. Although they do not have all nine essential amino acids, these proteins can make a complete protein when they are combined appropriately. The task may seem a bit daunting, but it is actually easy. The three groups of plant foods that are the best sources of protein are grains, cereals, beans and peas, and nuts and seeds. When at least two of these three groups are present in a meal or eaten separately throughout the day, your body can make a complete protein.