N-acetyltyrosine is a non-essential amino acid found in chicken, soy products and nuts which is synthesised from phenylalanine. A few studies using healthy volunteers, as well as those with depression or depressive disorders have been conducted to understand its role in mood and cognition. Certain evidence shows us that acute tryptophan depletion lowers energy levels and mood and increases irritability when following a diet deficient in this novel amino acid (Leyton et al., 2000). The impact on mood is also observed in those with acute phenylalanine or tyrosine depletion. One human volunteer study demonstrated that contentedness or happiness lowered and subjects became more apathetic, following ingestion of food materials without tyrosine and phenylalanine (McLean and Rubinsztein, 2003). It had been shown much earlier that administration of L-phenylalanine certainly improved mood in depressed patients treated with a selective monoamine oxidase B inhibitor (Sabelli and Javaid, 1995).
Measuring mood is not straightforward but it can be rated using Visual Analogue Mood Scales. This scale is altered following combined depletion of monoamines such as tyrosine, tryptophan and phenylalanine, but there were no significant differences found in the profile of mood states (POMS) (Hughes et al., 2004). In one study, a nutritionally balanced mixture that was deficient in phenylalanine and tyrosine impaired word recall, decreased scores for alertness and increased scores for anxiety in healthy male volunteers compared to a nutritionally balanced mixture containing these two amino acids (Grevet et al., 2002). It suggests these two amino acids are important factors in mood regulation and have a great bearing on our feelings and the link appears to be associated with N-acetyltyrosine.
Grevet, E.H., Tietzmann, M.R., Shansis, F.M., Hastenpflug, C., Santana, L.C., Forster, L., Kapczinski, F., Izquierdo, I. (2002) Behavioural effects of acute phenylalanine and tyrosine depletion in healthy male volunteers. J Psychopharmacology 16 (1) pp 51-55
Hughes, J.M., Matrenza, C., Kemp, A.H., Harrison, B.J., Liley, D., Nathan, P.J. (2004) Selective effects of simultaneous monoamine depletion on mood and emotional responsiveness. Intl. J. Neuropsychopharmacology 7 pp. 9-17.
Leyton, M. Young, S.N. Pihl, R. O. Etezadi, S. ,Lauze, C., Blier, P., Baker G.B., Benkelfat, C. (1999) A Comparison of the effects of acute tryptophan depletion and acute phenylalanine/tyrosine depletion in healthy women. Tyrptophan, serotonin and Melatonin: Basic Aspects and Applications pp. 67-71.
McLean, A. Rubinsztein, J.S. Robbins, T.W. Sahakian, J. (2004) The effects of tyrosine depletion in normal healthy volunteers: implications for unipolar depression. Psychopharmacology 171 286-297
Sabelli, H.C., Javaid, J.I. (1995) Phenylethylamine modulation of affect: therapeutic and diagnostic implications. J Neuropsychiatry Clin Neurosci 7 pp. 6-14
Leave a Reply