L-Phenylalanine - Glossary


An essential amino acid.  L-Phenylalanine is also the precursor to l-tyrosine as well as phenethylamine (PEA). It may be included in certain weight loss/bodybuilding supplements for this reason, as both metabolites have mood/cognitive effects.

Phenylalanine is a product of aspartame metabolism.  Various activists insist it’s (partly) responsible for the reputed (and often exaggerated) side effects of the sweetener, since it’s a “neurotoxin” when taken in isolation.  This claim is based on studies of phenylketonuria (PKU), a genetic disorder that affects phenylalanine metabolism.  However, there is no reason to believe that small amounts of phenylalanine, taken in supplemental form, will have any adverse effects on healthy people.

Author: elissa

Elissa is a former research associate with the University of California at Davis, and the author/co-author of over a dozen articles published in scientific journals. Currently a freelance writer and researcher, Elissa brings her multidisciplinary education and training to her writing on nutrition and supplements.

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