Am J Clin Nutr. 1995 Dec;62(6):1206-11.

Erythrocyte L-aspartyl-L-phenylalanine hydrolase activity and plasma phenylalanine and aspartate concentrations in children consuming diets high in aspartame.

Stegink LD, Lindgren SD, Brummel MC, Stumbo PJ, Wolraich ML.

Department of Pediatrics, University of Iowa College of Medicine, Iowa City, USA.

A deficit of alpha-aspartyl-phenylalanine (alpha-Asp-Phe) hydrolase activity has been suggested as a cause of possible adverse effects of aspartame ingestion. Twenty-five normal preschool children and 23 school-age children described by their parents as sensitive to sugar were fed diets high in sucrose, aspartame, or saccharin for three successive 3-wk periods. Blood samples were obtained at baseline (fasting) and within the last 3 d of each dietary period (postprandial). alpha-Asp-Phe concentrations were below detection limits (0.5 mumol/L) in all plasma samples and Phe and Asp concentrations remained within normal limits, alpha-Asp-Phe hydrolase activities in baseline hemolysate samples did not differ between groups. One subject had a plasma alpha-Asp-Phe hydrolase activity > 2 SD below the mean. Despite this low activity, this subject did not show consistent cognitive or behavioral anomalies that could be linked to low hydrolase activity.