Effects of rapid increase of phenylalanine intake in older PKU children.

Twelve children formerly on strick low-phenylalanine diets were allowed to change to a moderate-protein diet over a five-week period. They were observed at home by parents, in school by teachers, and in the clinic by team members, and were evaluated periodically for phenylalanine intake, serum phenylalanine levels, activity, irritability, growth, and intelligence. Growth patterns were normal for age. Dietary phenylalanine increased sharply for all children at the end of three months, then dropped at about six months, after which it rose above the three month level. Serum phenylalanine levels followed dietary intakes, and in nine cases are staying at about 20 mg. per 100 ml. or less. The three subject above 20 mg. have serum phenylalanine of 21, 23, and 25 mg. per 100 ml. One of these has had behavioral problems and excessive weight gains in the past two years.