Other name(s):

a-amino-b-[3-indollyl]-propionic acid

Unproven claims

There may be benefits that haven't yet been proven through research.

L-tryptophan may make you sleepy. It’s been used to treat insomnia. It may be a natural antidepressant and stress reducer. It may help treat hyperactivity in children. It may also treat manic episodes in people with bipolar disorder. L-tryptophan also decreases appetite. It may help treat symptoms of severe premenstrual syndrome (PMS). It may help people quit smoking, when used with other conventional treatment methods.

Recommended intake

L-tryptophan is an amino acid that is naturally found in animal and plant foods. After eating foods with L-tryptophan, your body converts it into serotonin, vitamin B-6, and melatonin. Experts advise that no one take L-tryptophan as a supplement. This is because it may be unsafe. It can make some health conditions worse.

Side effects, toxicity, and interactions

The use of L-tryptophan has been linked with a condition that can be fatal. This is called eosinophilic myositis. It is also called eosinophilia-myalgia (EMS). This issue was linked to L-tryptophan made by a Japanese company that had recently changed its chemical processes. The cause of the condition has been debated. Most experts doubt that L-tryptophan itself caused the problem. Instead, they think it may have been caused by something else in the compound.

Ongoing studies have found that 4,5-tryptophan-dione is likely at fault for this problem. In a study of over-the-counter L-tryptophan, this chemical was found to make up 0.5% to 10.3% of the samples of L-tryptophan. The FDA has allowed the sale of L-tryptophan since 2005. But you should only use L-tryptophan under the direction of a healthcare provider.

Don't take L-tryptophan if you take any of these medicines:

  • Antidepressants/anxiolytics (tricyclics, MAOIs, and SSRIs)

  • Monoamine oxidase inhibitors

  • Linezolid

  • Carbidopa

Online Medical Reviewer: Brittany Poulson MDA RDN CD CDE
Online Medical Reviewer: Diane Horowitz MD
Online Medical Reviewer: Heather M Trevino BSN RNC
Date Last Reviewed: 6/1/2021