Proteins are made up of amino acid chains which are divided into the essential amino acids and the non essential amino acids. The body makes up about half of the amino acids we need, but the essential amino acids must be gotten from food.
Proteins have numerous functions in the body. They provide the building material needed for growth and repair of tissues. They make up vital parts of our skin, nails, hair, membranes, muscles, teeth, bones, organs, ligaments and tendons. Proteins regulate enzyme activity; they serve as certain hormones working as chemical messengers around the body; they work as antibodies to assist in immune fuction and resistance to disease; they assist in regulating the fluid balance in body compartments and they help regulate the acid/base balance of body fluids; they transport nutrients in and out of our cells around the body; they provide energy in the form of calories. Wow! They do alot!
Which proteins are best to eat? There are complete and incomplete proteins. Incomplete proteins are primarily plant proteins, and although in combination of several different foods, they make up all the essential amino acids we need, individually they do not. Complete protein, such as animal or soy foods do have all the essential amino acids needed by the body to make its own protein. A combination of both works best to meet the body's needs.
So, when planning a meal, keeping in mind that 25% should be some form of protein, eat a variety of protein sources and you'll be covered!