NEUROPSYCHOLOGICAL AND BIOCHEMICAL INVESTIGATIONS IN HETEROZYGOTES FOR PHENYLKETONURIA DURING INGESTION OF HIGH-DOSE ASPARTAME (A SWEETENERCONTAINING PHENYLALANINE)

Aspartame, a high intensity sweetener, is use extensively worldwide in over 5,000 products. Upon ingestion, aspartame is completely metaboli zed to two amino acids and methanol (approximately 50% phenylalanine, 40% aspartic acid, and 10% methanol). The effects of aspartame on cogn itive function, electroencephalograms (EEGs) and biochemical parameter s were evaluated in 48 adult (21 men, 27 women) heterozygotes for phen ylketonuria (PKUH). PKUH subjects whose carrier status had been proven by DNA analysis ingested aspartame (either 15 or 45 mg/kg/day) and pl acebo for 12 weeks on each treatment using a randomized, double-blind, placebo-controlled, crossover study. A computerized battery of neurop sychological tests was administered at baseline weeks -2 and -1, and d uring treatment at weeks 6, 12, 18, and 24. Samples for plasma amino a cids and urinary organic acids were also collected during these visits . EEGs were evaluated by conventional and spectral analysis at baselin e week -1 and treatment weeks 12 and 24. The results of the neuropsych ological tests demonstrated that aspartame had no effect on cognitive function. Plasma phenylalanine significantly increased, within the nor mal range for PKUH, at 1 and 3 h following the morning dose of asparta me in the group receiving the 45 mg/kg per day dose only. There were n o significant differences in the conventional or spectral EEG analyses , urinary organic acid concentrations, and adverse experiences when as partame was compared with placebo. This study reaffirms the safety of aspartame in PKUH and refutes the speculation that aspartame affects c ognitive performance, EEGs, and urinary organic acids.