Amino acids are often described as the building blocks of protein, the second most abundant substance in the body after water, and essential to many internal processes. Proteins are actually made up of chains of amino acids linked together in combinations of varying complexity.

Amino acids fall into two categories: essential and non-essential. The sixty percent of amino acids that the human body can synthesise itself are classed as non-essential, while the remaining forty percent that must be obtained from the diet are classed as essential. However, dietary requirements for amino acids can differ and some non-essential amino acids may be considered "essential" by some.