Plasma tyrosine in normal humans: Effects of oral tyrosine and protein-containing meals

E. Melamed*, B. Glaeser, J. H. Growdon, R. J. Wurtman

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


To test the effects of tyrosine ingestion and concurrent food consumption on plasma tyrosine levels and on the plasma tyrosine ratio, we measured plasma neutral amino acid levels in 11 subjects who consumed a diet containing 113 g protein and who also took 100 mg/kg/day of L-tyrosine (in three equally divided doses) before meals. Plasma tyrosine levels rose significantly (p<0.025) during the day when subjects consumed the diet alone; they increased markedly after tyrosine ingestion (p<0.005). Tyrosine administration did not affect plasma concentrations of the other neutral amino acids that compete with tyrosine for entry into the brain. Thus, the plasma tyrosine ratio increased from 0.13 to 0.21 (p<0.001) on the day fed subjects received the tyrosine. These observations indicate that tyrosine administration might increase brain tyrosine levels and perhaps accelerate catecholamine synthesis in humans with diseases in which catecholamine synthesis or release is deficient.

Original languageEnglish
Pages (from-to)299-306
Number of pages8
JournalJournal of Neural Transmission
Issue number4
StatePublished - Dec 1980
Externally publishedYes


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