Dietary effects on brain serotonin synthesis: relationship to appetite regulation.

This review summarizes evidence showing that: 1) the synthesis of serotonin in the brain depends directly on the amount of tryptophan available to it from the circulation; 2) tryptophan uptake into brain depends on the blood levels not only of tryptophan, but also of other aromatic and branched-chain amino acids that compete with tryptophan for a common transport carrier into brain; and 3) dietary factors that influence the blood levels of tryptophan and these other amino acids can modify tryptophan uptake into brain, and consequently the rate of serotonin formation. Additionally, data are reviewed that attempt to show that appetite for protein and/or carbohydrates is dependent on the relationship between food intake, plasma amino acid pattern, brain tryptophan uptake, and serotonin synthesis.