Plasma, erythrocyte and human milk levels of free amino acids in lactating women administered aspartame or lactose.

Aspartame is a dipeptide (L-aspartyl-L-phenylalanyl methyl ester) with a sweetening potential of 180 to 200 times that of sucrose. Questions have been raised about the potential toxic effects of its constitu ent amino acids when the compound is ingested in large amounts by lactating women. Plasma, erythrocyte and milk levels of free amino acids were measured in six normal female subjects with established lactation after oral administration of either aspartame or lactose at 50 mg/kg body weight in a cross-over design. No significant change in plasma or erythrocyte aspartate levels was noted following aspartame or lactose administration. Plasma phenylalanine levels increased approximately fourfold over fasting values 45 minutes after aspartame loading ( P < 0.001 ), and returned to baseline by 4 hours. Erythrocyte phenylalanine levels showed similar changes. No statistically significant difference in milk aspartate or phenyl alanine levels between aspartame and lactose loading were noted using the paired i-test. When milk data were subjected to curve analysis using orthogonal polynomials (mean, linear, cubic, quadratic ), small, but statisti cally significant differences in overall milk aspartate (P —0.04,linear only) and phenylalanine ( P = 0.034, mean only ) levels were noted during the immediate 4 hour post-loading period. However, these small increases would not meaningfully affect aspartate or phenylalanine intake of an in fant. J. Nutr. 109: 2173-2181, 1979. INDEXING