font size



What other names is L-tryptophan known by?

L-Triptofano, L-Trypt, L-2-amino-3-(indole-3-yl) propionic acid, L-Tryptophane, Tryptophan.

What is L-tryptophan?

L-tryptophan is an amino acid, a protein building block that can be found in many plant and animal proteins. L-tryptophan is called an "essential" amino acid because the body can't make it. It must be acquired from food.

L-tryptophan is used for insomnia, sleep apnea, depression, anxiety, facial pain, a severe form of premenstrual syndrome called premenstrual dysphoric disorder (PMDD), smoking cessation, grinding teeth during sleep (bruxism), attention deficit-hyperactivity disorder (ADHD), Tourette's syndrome, and to improve athletic performance.

Possibly Effective for...

  • Treating premenstrual dysphoric disorder (PMDD). Taking 6 grams of L-tryptophan per day seems to decrease mood swings, tension, and irritability in women with PMDD.
  • Smoking cessation (helping people quit smoking). Taking L-tryptophan seems to improve the effectiveness of conventional treatment for smoking cessation.

Possibly Ineffective for...

  • Treating teeth grinding (bruxism).
  • Treating facial pain.
  • Improving athletic ability.

Insufficient Evidence to Rate Effectiveness for...

  • Depression. Developing research suggests that L-tryptophan might improve the effectiveness of common medications for depression.
  • Seasonal affective disorder (SAD). Early research suggests L-tryptophan might be helpful in SAD.
  • Attention deficit-hyperactivity disorder (ADHD). There is some evidence that L-tryptophan levels are lower in children with ADHD; however, taking L-tryptophan supplements does not appear to improve ADHD symptoms.
  • Treating sleep disorders. Taking L-tryptophan might decrease the amount of time it takes to fall asleep and improve mood in healthy people with sleep problems. There is also some evidence that taking L-tryptophan might decrease episodes in some people who periodically stop breathing during sleep (sleep apnea).
  • Anxiety.
  • Other conditions.
More evidence is needed to rate L-tryptophan for these uses.

Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, and Insufficient Evidence to Rate (detailed description of each of the ratings).

Therapeutic Research Faculty copyright

Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Medical Dictionary