The ‘building blocks’ of protein are called amino acids. In MSUD, due to the lack of an enzyme, the body cannot properly deal with three amino acids, leucine, isoleucine and valine - collectively known as the branched chain amino acids (BCAAs). People with MSUD therefore need to severely restrict the amount of protein they eat.
A key element in the management of MSUD is the use of protein substitutes. Protein substitutes for MSUD provide all the amino acids found in protein but no leucine, isoleucine or valine. In combination with the small allowance of regular dietary protein, protein substitutes ensure that an individual with MSUD has an adequate intake of protein.