Nutritional value of essential amino acids in the treatment of adults with phenylketonuria

The present short-term N-balance study in adult PKU patients receiving a mixture of LNAA establishes a limited retention of nitrogen. Whether lysine could be the limiting amino acid remains to be determined by new short-term N-balance studies, with lysine added to the LNAA mixture. Therefore, special caution should be taken in the long-term use in PKU patients of LNAA without any added lysine.