L-tryptophan is an amino acid used for sleep apnea, insomnia, depression, anxiety, attention deficit hyperactivity disorder and other conditions, according to WebMD. Taking 6 grams of L-tryptophan each day is effective in the treatment of premenstrual dysphoric disorder, or PMDD. It also improves success with quitting smoking when taken in conjunction with conventional treatments.
The body uses tryptophan to create niacin, a B vitamin that plays a key role in digestion, skin and nerve health, and serotonin production, explains WebMD. Serotonin is a brain chemical that makes a person feel relaxed and happy. It is also used in the production on melatonin, a hormone that controls sleep and wake cycles.
L-tryptophan is called an essential amino acid because the body cannot produce it, notes MedlinePlus. It must be ingested from food or supplements. Foods rich in tryptophan include turkey and other poultry, meat, yogurt, cheese, eggs, and fish.
The presence of tryptophan in turkey leads many to blame the food for Thanksgiving Day sleepiness and sluggishness, but turkey contains no more tryptophan than other kinds of poultry, says WebMD. If a person feels sleepy after eating Thanksgiving dinner, it is more likely a result of overeating than specifically eating turkey.