Tryptophan and tyrosine availability: relation to food choice and sleeping habits of man. A preliminary study

Brain serotonin and noradrenaline may be involved in the regulation of sleep and of food choice. The precursor amino acids tryptophan and tyrosine and their ratios to large, neutral amino acids (LNAA) were determined in plasma of 60 healthy females and related to sleeping and eating habits as reported on a questionnaire. There was no relation between biochemical findings and the habits of going early to bed and rising early versus late rising and going late to bed. The ratios tryptophan:LNAA and tyrosine:LNAA together were significantly related to the choice of between-meal snacks in the forenoon; the subjects with supernormal net availability of tryptophan and tyrosine selected snacks with low proportions of protein to carbohydrate contents in preference to snacks with relatively high proportions as compared with subjects with subnormal net availability. Although designed as a pilot study, the results suggest an involvement of both serotoninergic and noradrenergic mechanisms in the regulation or protein and carbohydrate intake in man.