Plasma and erythrocyte amino acid levels of adult humans given 100 mg/kg body weight aspartame

Abstract

Blood amino acid and methanol levels were measured in 6 fasting adult subjects (3 male, 3 female) administered an abuse dose of aspartame (100 mg/kg body wt) in both solution and slurry form. A randomized cross-over design was used. Greater variation in blood aspartate, phenylalanine and methanol levels was noted when aspartame was administered in slurry form. Blood aspartate, phenylalanine and methanol levels did not exceed those associated with toxic findings in any case. Plasma aspartate levels increased from mean (± S.D.) baseline levels of 0.16 ± 0.05 μmol/dl to peak values of 0.43 ± 0.23 ( P = 0.02) 30 min after administration in solution. Plasma aspartate levels increased to peak values of 3.6 and 5.8 μmol/dl at 30–45 min in 2 of 6 subjects given aspartame in slurry form, while levels in the other 4 subjects were unchanged from baseline values. Erythrocyte aspartate levels were unchanged in all subjects. Plasma and erythrocyte phenylalanine levels increased significantly ( P = 0.001) after both solution and slurry administration. Plasma phenylalanine levels reached mean (± S.D.) peak values of 20.3 ± 2.05 and 26.0 ± 18.9 μmol/dl respectively 45 min after loading. The higher variation after slurry administration reflected 2 subjects with peak values of 45.8 and 51.3 μmol/dl. Blood methanol levels increased after both solution and slurry administration, reaching mean (± S.D.) levels of 1.16 ± 0.47 and 1.27 ± 0.48 mg/dl respectively 60–90 min after loading.