Nutrition: Proteins
Next to water, proteins are the most abundant substances in the human body. Proteins are major components of nearly every cell and have been called the “body builders” because of their role in developing and repairing bone, muscle, skin, and blood cells. They are the key elements of the antibodies that protect us from disease, of enzymes that control chemical activities in the body, and of hormones that regulate body functions. Proteins help transport iron, oxygen, and nutrients to all body cells and supply another source of energy to cells when fats and carbohydrates and not readily available. In short, adequate amounts of protein in the diet are vital to many body functions and ultimately to survival.
Whenever you consume proteins, your body breaks them down into smaller molecules known as amino acids, the building blocks of protein. Dietary protein that supplies all of the essential proteins is called complete (high quality) protein. Typically, protein from animal products is complete. Proteins from plant sources are often incomplete proteins in that they may lack one or two of the essential proteins that the body cannot produce on its own. Nevertheless, it is relatively easy for the vegetarian to combine plant foods effectively and eat complementary sources of plant protein. An excellent example of this mutual supplementation process is eating peanut butter on whole grain bread. Although each of these foods lacks certain essential amino acids, eating them together provides complete protein.
A person might need to eat extra protein of fighting off a serious infection, recovering from surgery or blood loss, or recovering from burns. In these instances, proteins that are lost to cellular repair need to be replaced. There is considerable controversy over whether someone in high-level physical training needs additional protein to build and repair muscle fibers or whether normal daily requirements should suffice.
