Proteins are made up of amino acids (H, C, O, N, S, P, Fe) joined together in long chains and chemical combinations. The body requires 20 different amino acids.

Eight amino acids cannot be synthesised in the body and are termed "essential amino acids" which must be consumed in the diet. The remaining amino acids can be synthesised from compounds ordinarily found in the body. It is easier for non-vegetarians to eat essential amino acids as good sources are diary products, meat fish and poultry. However, all the amino acids can be gained from plants if a very wide range are eaten.

Proteins provide the building blocks for the synthesis of cellular material. The RDA for adults for protein is 0.83g per kg of body weight. Evidence suggests that training may require slightly more protein intake. Protein catabolism during exercise is most apparent when glycogen stores are low and the protein is usable as a substitute fuel through Gluconeogenesis (the process of glucose synthesis, especially from protein).