Sleep scientists at the University of Sydney have found that nutritionally balanced high glycaemic index (GI)meal can significantly increase the presence of tryptophan - an amino acid known to induce sleepiness.
The study, by PhD student Christopher Herrera and his colleagues and presented at the Australasian Sleep Association Conference, concludes that the type of food you eat can dramatically affect the presence or absence of important sleep-inducing hormones.
To reach the conclusion, Herrera's team fed their subjects one of three meals: a completely carbohydrate high-GI meal, a mixed carbohydrate and protein high-GI meal, or a mixed low-GI meal, reports ABC Online.
After four hours they measured the levels of glucose, insulin and amino acids present and compared the results across the three varieties of meal.
From analyses, they found that a high-GI rice-only meal prompted the largest release of insulin and the highest ratio of tryptophan to other amino acids. The high-GI meal prompted a similar, but smaller response.
"After high GI foods, you see increased availability of tryptophan," says Herrera. "And there is a dose response, so that the higher the glycaemic response to a meal, the greater the availability of tryptophan is to the brain."