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.
Reduction of brain dopamine concentration with dietary tyrosine
plus phenylalanine depletion: an [11C]raclopride PET study
Imperial College, School of Medicine, University Department
of Psychiatry, Warneford Hospital, Oxford, UK
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