In a person suffering from phenyl ketonuria, which of the following should be restricted in diet?

Phenylalanine is an essential amino acid. Deficiency of Pheny alanine hydroxlase os cause for the phenylketonuia. Early detection is very impant. About 5 units of IQ are lost for each 10-week delay in staing the treatment. The treatment is to provide a diet containing low phenylalanine.Food based on tapioca 9cassava0 will have low phenyl alanine content. The special diet is to be continued during the first decade of life. REF :DM VASUDEVAN TEXTBOOK ;7th EDITION;Page no ;237.