Proteins are often called the building blocks of the body. Protein consists of combinations of structures called amino acids that combine in various ways to make muscles, bone, tendons, skin, hair and other tissues. They serve other functions as well, including nutrient transportation and enzyme production. In fact, over 10,000 different proteins are present in the body.
Adequate, regular protein intake is essential because it isn't easily stored by the body. Various foods supply protein in varying amounts with complete proteins (those containing 8 essential amino acids), coming mostly from animal products such as meat, fish and eggs and incomplete protein (lacking one or an essential amino acid) coming from sources such as vegetables, fruits and nuts. Vegetarian athletes may have trouble getting adequate protein if they aren't aware of how to effectively combine foods.