The ‘building blocks’ of protein are called amino acids. In HCU, due to the lack of an enzyme, the body cannot properly deal with one of the amino acids, methionine. People with HCU therefore need to severely restrict the amount of protein they eat.
A key element in the management of HCU is the use of protein substitutes. Protein substitutes for HCU provide all the amino acids found in protein but no methionine. In combination with the small allowance of regular dietary protein, protein substitutes ensure that an individual with HCU has an adequate intake of protein.