L-tryptophan
Other name(s):
a-amino-b-[3-indolyl]-propionic acid
What is L-tryptophan?
L-Tryptophan is an essential amino acid. This means it isn't made by the body and must come from your diet. L-tryptophan is important for making proteins. Red meat, poultry, dairy, and eggs are good sources of L-tryptophan.
Unproven claims
There may be benefits that haven't been proven yet 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 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). 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.
If you have diabetes, talk with your healthcare provider before using L-tryptophan.
People who are pregnant or breastfeeding should talk with a healthcare provider before taking any herbal or dietary supplements.
Don't take L-tryptophan if you take any of these medicines:
Online Medical Reviewer:
Brittany Poulson MDA RDN CD CDE
Online Medical Reviewer:
Stefania Manetti
Date Last Reviewed:
9/1/2025