The effects that diet has on sleep are based on, above all else, the fact that tryptophan and some other nutrients are needed to produce serotonin and melatonin. Tryptophan has been noted to increase subjectively-experienced sleepiness and to improve the quality of sleep (Jenkins 2016).
For enough tryptophan to reach the brain, it is important to select foods which have as much tryptophan as possible in ratio to other large neutral amino acids (LNAA). This is because these amino acids compete with tryptophan in order to be transported across the blood-brain barrier to the brain.
A good, natural source of tryptophan is pumpkin seed powder. When consumed in the evenings, enough tryptophan is present to make possible improvement of quality of sleep (Hudson 2005). In addition to pumpkin seed powder, enough carbohydrates should be consumed, due to the metabolism of tryptophan requiring a small increase in insulin, in order for the tryptophan levels in the brain to rise sufficiently. Consumption of whey protein and branched-chain amino acids (BCAA) should be avoided in the evenings because the other large neutral amino acids they contain decrease the amount of tryptophan crossing over the blood-brain barrier into the brain. The use of tryptophan as a supplement can be considered questionable, as its use has been linked to serious, though rare side effects. These effects may have been caused by contaminations in the tryptophan supplements.
Eating heavy meals during the last four hours before going to sleep should be avoided, as a heavy meal can impair sleep. The newest studies have shown that people who have a versatile gut microbiome generally also sleep better (Smith 2019). A good microbiome can be maintained and fixed by following a quality diet rich in fruits and vegetables. Consuming yogurt is also recommended, as it is a good source of probiotics. Following a Mediterranean diet has been shown to have good effects on the quality of sleep (Campanini 2017).