Amino acids are often referred to as the building blocks of proteins, and the proteins and enzymes that are comprised of these amino acids make up muscle, hormones, neurotransmitters, and much else that makes the body run smoothly. A healthy body requires twenty different amino acids, several of which are produced by the body itself. However, eight of these can only be gotten through diet or supplement, and many of the others often need a boost due to a variety of factors, including diet, age, exercise, infection, and stress levels. Amino acid supplements can aid in making a body healthy, and fighting conditions such as fatigue. They are particularly useful for body builders and weight trainers, as amino acids are essential for muscle building, maintenance and repair.