Aspartame is another artificial sweetener. It is a dipeptide, consisting of L-aspartic acid and the methyl ester of L-phenylalanine.
In the gastrointestinal tract, aspartame undergoes complete hydrolysis into its three components aspartic acid, phenylalanine, and methanol (Figure 9.6).
Although aspartame has been approved (the ADI is set at 50 mg/kg body weight per day) as a sweetener in many countries, there are still some toxicological aspects under consideration. A small number of urticarial reactions have been demonstrated. In general, it is agreed that the methanol and aspartic acid formed from aspartame by hydrolysis are safe. As far as the third component, phenylalanine, is concerned, there is the possibility of combined action. Interactions between phenylalanine and other amino acids are suggested at the level of amino acid transport, leading to nervous disturbances as a result of decreased neurotransmitter levels. Formation of phenylalanine from aspartame can actually pose a risk for so-called homozygous phenylketonurics. These people lack the ability to hydroxylate phenylalanine, the first step in its metabolism.
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