Plasma and erythrocyte concentrations of free amino acids in adult humans administered abuse doses of aspartame

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Abstract
Plasma and erythrocyte concentrations of amino acids were measured in 18 fasting adult subjects (9 male, 9 female) administered abuse doses of aspartame (100, 150, and 200 mg/kg body weight) dissolved in 500 ml orange juice. Six subjects were studied at each dose. Plasma aspartate concentrations increased significantly (p ≤0.05) over baseline values after ingestion of each dose. However, the increase was small in each case, and maximal levels observed were below those noted postprandlally in formula‐fed infants. No significant changes (p>0.05) were noted in erythrocyte glutamate, or erythrocyte aspartate concentrations after any dose. Plasma phenylalanine concentrations increased significantly over fasting concentrations (p≤0.01) from 15 min to 6 h after each dose, and the increase was proportional to dose. Mean (±SD) peak plasma phenylalanine concentrations were 20.3 ± 2.03, 35.1 ±11.3, and 48.7 ± 15.5 μmol/dl, respectively, after aspartame doses of 100, 150, and 200 mg/kg, Erythrocyte phenylalanine concentrations showed similar changes. Although these phenylalanine concentrations are considerably above the normal postprandial range (12 ± 3 μmol/dl), they are below values associated with toxic findings. These data indicate little risk to normal subjects from excessive aspartate or phenylalanine levels after ingestion of single abuse loads of aspartame.