Eleven hyperactive boys were treated for 2 weeks with D-phenylalanine
(20 mg/kg per day) and for 2 weeks with placebo in a double-blind crossover
study. Tests included parent and teacher behavior ratings, cognitive
measures, and blood and urine measures of norepinephrine, amino acids, and
trace amines. No significant improvement or deterioration in behavior and
no side effects were noted, and only serum phenylalanine was increased by
the active treatment phase. This provides reassurance about the toxicity of
aspartame, a food additive that contains phenylalanine, but argues against
precursor loading treatment of hyperactivity.
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