Overview

L-Tryptophan is an essential amino acid that is necessary for making proteins. It is naturally found in red meat, poultry, eggs, and dairy.

L-tryptophan is important for many organs in the body. L-tryptophan is not made by the body and must be consumed from the diet. After absorbing L-tryptophan from food, the body converts some of it to 5-HTP and then to serotonin. Serotonin is a hormone that transmits signals between nerve cells. Changes in serotonin levels in the brain can affect mood.

People use L-tryptophan for severe PMS symptoms, depression, insomnia, and many other conditions, but there is no good scientific evidence to support any of these uses.

Uses & Effectiveness

Possibly Ineffective for

  • Depression. Taking L-tryptophan by mouth doesn't seem to be beneficial in patients with depression. Also, it may increase the risk of side effects of some medications.

There is interest in using L-tryptophan for a number of other purposes, but there isn't enough reliable information to say whether it might be helpful.

Side Effects

When taken by mouth: L-tryptophan occurs naturally in many foods, and is consumed as part of the diet. L-tryptophan supplements are possibly safe when taken for up to 3 weeks. L-tryptophan can cause some side effects such as drowsiness, stomach pain, vomiting, diarrhea, headache, blurry vision, and others.

In 1989, L-tryptophan was linked to cases of a neurological condition called eosinophilia-myalgia syndrome (EMS). But these cases might be due to contamination. About 95% of all EMS cases have been traced to L-tryptophan produced by a single manufacturer in Japan.

There isn't enough reliable information to know if L-tryptophan is safe when taken for more than 3 weeks.

Special Precautions and Warnings

When taken by mouth: L-tryptophan occurs naturally in many foods, and is consumed as part of the diet. L-tryptophan supplements are possibly safe when taken for up to 3 weeks. L-tryptophan can cause some side effects such as drowsiness, stomach pain, vomiting, diarrhea, headache, blurry vision, and others.

In 1989, L-tryptophan was linked to cases of a neurological condition called eosinophilia-myalgia syndrome (EMS). But these cases might be due to contamination. About 95% of all EMS cases have been traced to L-tryptophan produced by a single manufacturer in Japan.

There isn't enough reliable information to know if L-tryptophan is safe when taken for more than 3 weeks.

Pregnancy: It is possibly unsafe to take L-tryptophan in amounts greater than those found in foods during pregnancy. It might harm the unborn child.

Breast-feeding: There isn't enough reliable information to know if L-tryptophan is safe to use when breast-feeding. Stay on the safe side and stick to food amounts.

Interactions

    Moderate Interaction

    Be cautious with this combination

  • Serotonergic drugs interacts with L-Tryptophan

    L-tryptophan might increase a brain chemical called serotonin. Some medications also have this effect. Taking L-tryptophan along with these medications might increase serotonin too much. This might cause serious side effects including heart problems, seizures, and vomiting.

  • Sedative medications (CNS depressants) interacts with L-Tryptophan

    L-tryptophan might cause sleepiness and slowed breathing. Some medications, called sedatives, can also cause sleepiness and slowed breathing. Taking L-tryptophan with sedative medications might cause breathing problems and/or too much sleepiness.

Dosing

L-tryptophan supplements have most often been used by adults in doses of 60 mg by mouth daily for 16 weeks. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Keep in mind that some dietary supplement products might not list L-tryptophan separately on the label. Instead, it might be listed under niacin. Niacin is measured in niacin equivalents (NE). 60 mg of L-tryptophan is the same as 1 mg NE.
View References
Show More Show Less

CONDITIONS OF USE AND IMPORTANT INFORMATION: This information is meant to supplement, not replace advice from your doctor or healthcare provider and is not meant to cover all possible uses, precautions, interactions or adverse effects. This information may not fit your specific health circumstances. Never delay or disregard seeking professional medical advice from your doctor or other qualified health care provider because of something you have read on WebMD. You should always speak with your doctor or health care professional before you start, stop, or change any prescribed part of your health care plan or treatment and to determine what course of therapy is right for you.

This copyrighted material is licensed from Therapeutic Research Center, LLC. Information from this source is evidence-based and objective, and without commercial influence. For professional medical information on natural medicines, see Natural Medicines Comprehensive Database Professional Version.
Licensed from Therapeutic Research Center, LLC
Copyright © 1995-2025 by Therapeutic Research Center, LLC. All Rights Reserved.