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Regul Toxicol Pharmacol. 2002 Apr; 35(2 Pt 2):S17-25.

Metabolism of Aspartame

Numerous studies have evaluated the metabolism of aspartame and the pharmacokinetics of its components - aspartate, phenylalanine, and methanol. Such studies have involved healthy adults, infants, children, and adolescents, PKU heterozygous adults, PKU homozygous individuals, and individuals sensitive to MSG. Studies included acute-dose, repeated-dose, and long-term dose regimens. In healthy adults and children, even after enormous doses, aspartame does not result in plasma concentrations of its components that are of safety concern. Plasma aspartate concentrations remained within the normal range even after bolus doses of aspartame as high as 200 mg/kg. The doses of aspartame used in studies with the other subpopulations have ranged from 4 to 100 mg/kg body wt. Plasma phenylalanine concentrations observed after large-bolus and repeated doses of aspartame were comparable to the normal postprandial range in both healthy adults and PKUH and well below those in untreated PKU. Blood methanol concentrations were not detectable after aspartame doses as high as 34 mg/kg body wt when ingested as a single bolus or about 70 mg/kg body wt when administered as eight divided doses at hourly intervals. Regardless of dose, blood formate concentrations did not change from baseline levels after aspartame administration. Evaluations of urinary formate excretion after single bolus doses of aspartame as high as 200 mg/kg body t demonstrated the body's ability to rapidly metabolize methanol and excrete formate. Thus, even when administered at levels well above 90th percentile average daily consumption, the risk of adverse effects from aspartame or its metabolic components is negligible, strongly supporting the safety of aspartame under its intended conditions of use.