What is the Best Age to Discontinue the Low Phenylalanine Diet in Phenylketonuria ?

Abstract

Followup of two groups of children with phenylketonuria who had been treated with low phenylalanine diets revealed no significant deterioration in their intellectual ability after the diets were stopped. Visual-perceptual problems were dis covered which may have interfered with school performance; this suggests a need for followup through the school years.

Long Term Studies of Untreated Phenylketonuria I: Intelligence or Mental Ability

“…a specific reading disability) may be detected in a normal child but has no likelihood at all of being discovered in the severely retarded. The most that one can predict from the present findings is that no catastrophic change in intelligence would be expected from termination of dietary treatment beyond the age of about 4 years and, in our own experience and that of others (Johnson 1972, Holtzman et al 1975, this seems to be the case.…”

“…Studies of treated phenylketonurics tend to confirm this pattern of brain damage since, in general, the earlier in life a low phenylalanine diet is started, the higher the intelligence in later childhood (eg. Knox 1972, Johnson 1972, Sibinga and Friedman 1972. What is not clear is at what age, if at all, the diet may be safely stopped without risk of further brain damage.…”

Diet in Phenylketonuria: How Long?

“…It is remarkable that already 25 years ago it was reported that in 13 of 14 PKU children whose diet had been stopped completely at the age of 6-9 years, no decrease in intellectual performance and behaviour was observed [3].…”