A recent paper from Oxford University has documented in patients using PET scanning documented that tyrosine deficiency in the diet resulted in reduced catecholamine function. Thus, patients with a reduced protein intake will have a tyrosine deficiency. These patients will have reduced catecholamine production. Since catecholamines, particularly norepinephrine and dopamine, control hunger, the catecholamine dysfunction will result in increased difficulty in controlling appetite. Editors.

Reduction of brain dopamine concentration with dietary tyrosine plus phenylalanine depletion: an [11C]raclopride PET study

Montgomery,A.J.; McTavish,S.F.

Imperial College, School of Medicine, University Department of Psychiatry, Warneford Hospital, Oxford, UK

Am.J.Psychiatry: 160:187-189:2003

OBJECTIVE: Extracellular dopamine concentrations were estimated through measurement of [(11)C]raclopride binding with positron emission tomography after dietary manipulation of the dopamine precursors tyrosine and phenylalanine. METHOD: Healthy male subjects were scanned on two occasions: once after receiving a balanced amino acid drink and once after receiving a drink mixture from which tyrosine and phenylalanine were omitted. RESULTS: Dietary tyrosine and phenylalanine depletion increased[(11)C]raclopride binding in the striatum by a mean of 6%. The change in [(11)C]raclopride binding correlated significantly with the fall in the ratio of tyrosine and phenylalanine to large neutral amino acids. CONCLUSIONS: This is the first demonstration of an effect of a dietary manipulation on brain dopamine release in humans. This result provides support for the further investigation of the role of dietary manipulations in the treatment of neuropsychiatric disorders