The Effects of Aspartame on Human Mood, Performance, and Plasma Amino Acid Levels
Consumption of the artificial sweetener aspartame raises plasma phenylalanine levels, thereby increasing brain phenylalanine and, conceivably, affecting the syntheses of monoaminergic brain neurotransmitters known to underlie various types of behavior. We have thus assessed the effects of single aspartame doses on certain types of behavior, particularly those relating to mood and performance. In a double-blind, placebo-controlled, crossover study, a single dose of aspartame (60 mg/kg), or the same dose in combination with 37 g of carbohydrate, was administered to 20 male volunteers. [Carbohydrates enhance the entry of circulating phenylalanine into the brain by lowering plasma levels of competing large neutral amino acids (LNAA)]. A lower dose of aspartame (20 mg/kg) was also tested. Aspartame alone, or in combination with carbohydrate, did not alter any aspect of behavior that we assessed, nor did it produce detectable side effects. The ratios of plasma phenylalanine and tyrosine concentrations to those of the other LNAA were significantly increased by administration of aspartame. Since anecdotal reports of aspartame-associated neurological or behavioral side effects almost always describe effects as occurring after multiple aspartame exposures, it would be important to repeat our study using a protocol involving repeated aspartame administration.
KeywordsDigit Symbol Substitution Test Plasma Phenylalanine Stanford Sleepiness Scale Mood Questionnaire Plasma Amino Acid Level
Unable to display preview. Download preview PDF.
- Hoddes, E., Dement, W., and Zarcone, V. (1972). The history and use of the Stanford Sleepiness Scale. Psychophysiology 9:150.Google Scholar
- Lieberman, H.R., Spring, B.J., and Garfield, G.S. (1986b). The behavioral effects of food constituents: strategies used in studies of amino acids, protein, carbohydrate and caffeine. Nutr. Rev. 44 (suppl.):61–70.Google Scholar
- Maher, T.J., and Wurtman, R.J. (1983). High doses of aspartame reduce blood pressure in spontaneously hypertensive rats. N. Engl. J. Med. 309:1125.Google Scholar
- McNair, P.M., Lorr, M., and Droppleman, L.F. (1971). Profile of Mood States Manual, Educational and Industrial Testing Service, San Diego, California.Google Scholar
- Wurtman, R.J., Hefti, F., and Melamed, E. (1981). Precursor control of neurotransmitter synthesis. Pharmacol. Rev. 32:315–335.Google Scholar