The ‘building blocks’ of protein are called amino acids. In Tyrosinaemia, due to the lack of an enzyme, the body cannot properly deal with one of the amino acids, tyrosine. (As the body uses another amino acid, called phenylalanine, to make tyrosine, there are also problems with excessive intakes of phenylalanine.) People with Tyrosinaemia therefore need to severely restrict the amount of protein they eat.
A key element in the management of Tyrosinaemia is the use of protein substitutes. Protein substitutes for Tyrosinaemia provide all the amino acids found in protein but no tyrosine or phenylalanine. In combination with the small allowance of regular dietary protein, protein substitutes ensure that an individual with Tyrosinaemia has an adequate intake of protein.