Abstract
The objective of this thesis is to question the relationship between diet and sleep in Man, by means of a model relating carbohydrate intake, plasma amino acids, and sleep patterns. Experimental findings suggest that hunger, starvation and weight loss are associated with various measures of increased arousal, while satiety, food intake and weight gain correlate with decreased arousal. The relationship can be observed biochemically, physiologically, behaviorally and psychologically. Lowered arousal after eating in turn correlates with a variety of factors ranging from the age, sex and habits of the individual to the temperature, quantity and nature of the food eaten. The relationship has been consistently reported with carbohydrate. Carbohydrate may function to lower arousal via the pathway to brain serotonin, a neurotransmitter thought to mediate sleep. Evidence suggests that the insulin response to ingested carbohydrate results in an advantage for L-tryptophan in competition with other neutral amino acids for blood/brain transfer. Brain tryptophan concentration is the rate-limiting factor in serotonin synthesis. To test this model, twelve young men were given either fat, carbohydrate, protein or no supplement, in the form of a drink with the evening meal, in balanced order. Plasma was sampled hourly throughout the night and analysed for tryptophan, tyrosine and phenylalanine. The Subject's sleep was recorded electrophysiologically. The results showed the carbohydrate supplement to be associated with an increased ratio of tryptophan to tyrosine, compared with the other diets. The ratio of tryptophan to tyrosine plus phenylalanine was greatest with protein. EEG sleep did not vary with the amino acid ratios, however subjects chose to go to bed earlier after carbohydrate supplement.