L-tryptophan is an essential amino acid necessary for the production of serotonin. Some people find that boosting their L-tryptophan levels helps alleviate the symptoms of depression or insomnia. However, specific L-tryptophan dietary supplements were banned by the U.S. Food and Drug Administration in 1990 after an outbreak of eosinophilic-myalgia syndrome among users of the supplement. The EMS outbreak was traced to a contaminated batch of supplement; L-tryptophan occurs naturally in food and there is no danger of EMS from eating foods which contain tryptophan.
Pumpkin seeds are a natural source of L-tryptophan, with a tryptophan content of 0.576 grams per 100 grams of dried pumpkin seeds. Roasted pumpkin seeds, with or without added salt, have a slightly lower tryptophan content.
Milk and Dairy
Milk naturally contains a small amount of L-tryptophan. In her 2010 book, "Weight Control and Slimming Ingredients in Food Technology," Susan Cho states that L-tryptophan in milk played a part in increasing the sense of satiation or fullness when dietary protein was also consumed. It is believed that this phenomenon relates to the increased production of serotonin when L-tryptophan levels are raised. Therefore, Cho recommends the consumption of milk and dietary protein together as a way to aid weight loss. Other dairy products also contain L-tryptophan; eggs, for example, have 0.167 grams of tryptophan in every 100 grams uncooked. The L-tryptophan content of an egg remains almost the same, 0.166 grams, when cooked.
Turkey is notoriously known for its tryptophan content, although in fact it contains no more L-tryptophan per 100 grams than any other meat. All meats are sources of L-tryptophan, although the effects of such levels of L-tryptophan on the brain are negligible unless you eat the meat on an empty stomach with no other protein present. The popular belief that turkey at Thanksgiving causes sleepiness is a myth; sleepiness after a turkey feast is more likely due to general overeating and alcohol consumption.