It is thought that a carbohydrate-rich or a high-glycemic-index meal can affect sleep through its effects on tryptophan (an essential amino acid) levels.[1] More specifically, high-glycemic-index carbohydrates cause a rise in insulin levels, which drive circulating large neutral amino acids (LNAAs)[2] into muscles. Because LNAAs compete with tryptophan for transport across the blood-brain barrier, lower levels of blood LNAAs result in a higher tryptophan-to-LNAA ratio, so more tryptophan can travel to the brain. More tryptophan entering the brain leads to greater production of serotonin,[3] and, finally, to the secretion of melatonin (a sleep-inducing hormone), resulting in sleepiness.
How exactly does eating carbohydrates or a high GI meal close to bedtime help sleep?
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•Last Updated: May 16, 2025
Eating carbohydrates or high-glycemic-index meals before bedtime may enhance sleep by increasing insulin levels, which lowers circulating levels of large neutral amino acids and allows more tryptophan to enter the brain. This increase in tryptophan leads to greater serotonin production and ultimately boosts melatonin secretion, which promotes sleepiness.