There are several studies suggesting that eating foods high in tryptophan, serotonin or melatonin can improve our sleep quality. Tryptophan can be converted in our digestive tract to serotonin and moved up to our brain where it is converted to melatonin.
Below are two short lists of common foods that are particularly high in serotonin and melatonin.
Serotonin content in fruits and nuts (micrograms per gram):
white walnut 398
black walnut 304
English walnuts 87
Foods High in Melatonin (ng/100g):
Tart (sour) cherries 1,350
Mustard Seed 191.33
Ginger root 142.30
Fresh mint 49.66
** It is interesting to note that walnuts and tomatoes come up on both the serotonin and melatonin lists.