Some observations on the dietary treatment of phenylketonuria

Abstract

I N 1 9 5 3 , Bickel and his associates 1 at the suggestion of Dr. L. I. Woolf, prepared a special protein hydrolysate low in phenylalanine content. When this was administered to a phenylketonuric child, the plasma phenylalanine level was greatly reduced and phenylpyruvic acid disappeared from the urine. During the past decade, a number of retrospective studies 2-~~ have suggested that the low-phenylalanine diet may be effective in preventing some of the mental retardation associated with classical phenylketonuria, particularly if it is instituted at an early age. Recently, Birch and Tizard ~ have challenged these conclusions by pointing out that there are biases of selection inherent in the methods of 'ascertainment. Children selected for biochemical study because they have already been noted to be mentally retarded will upon examination be found to have low intelligence quotients (I.Q.) when compared with those selected at younger ages through affected relatives or screening programs. This communicat ion presents findings which are at variance with those by Birch and Tizard. 1~ These studies are based upon observations made on 37 children with phenylketonuria who have been treated with a low-phenylalanine diet and are 3 years of