Also indexed as:Tryptophan
L-Tryptophan: Main Image

L-Tryptophan is an essential amino acid that the body requires to synthesize proteins and specialized molecules such as the neurotransmitter serotonin. Serotonin appears to play significant roles in sleep, emotional moods, pain control, inflammation, intestinal peristalsis, and other body functions.1

  • Reliable and relatively consistent scientific data showing a substantial health benefit.
  • Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
  • For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

Our proprietary “Star-Rating” system was developed to help you easily understand the amount of scientific support behind each supplement in relation to a specific health condition. While there is no way to predict whether a vitamin, mineral, or herb will successfully treat or prevent associated health conditions, our unique ratings tell you how well these supplements are understood by the medical community, and whether studies have found them to be effective for other people.

For over a decade, our team has combed through thousands of research articles published in reputable journals. To help you make educated decisions, and to better understand controversial or confusing supplements, our medical experts have digested the science into these three easy-to-follow ratings. We hope this provides you with a helpful resource to make informed decisions towards your health and well-being.

This supplement has been used in connection with the following health conditions:

Used for AmountWhy
1 to 2 grams at bedtime 3 stars[3 stars]
L-tryptophan has been used successfully for people with insomnia in many studies,including double-blind trials.
2 to 4 grams per day 3 stars[3 stars]
Double-blind research has also shown that oral L-tryptophan can increase tolerance to acute pain.
Premenstrual Syndrome
2 to 6 grams per day, during the second half of the menstrual cycle 3 stars[3 stars]
Some research suggests that L-tryptophan may help balance mood symptoms associated with PMS.
Bipolar Disorder
Refer to label instructions 2 stars[2 stars]
Supplementation with L-tryptophan has led to improvement in depression in many studies, though its effect on bipolar disorder needs more study.
3 to 6 grams per day 2 stars[2 stars]
Several controlled trials have found L-tryptophan as effective as antidepressant medications. Depressed people should consult a doctor before use.  
1,000 mg three times daily before meals2 stars[2 stars]
Preliminary clinical trials suggest that serotonin precursors such as L-tryptophan might help control appetite and promote weight loss.
Obsessive-Compulsive Disorder
6 grams per day (only under a doctor's supervision) 2 stars[2 stars]
With a doctor's supervision, some people with OCD have experienced some symptom relief from supplementing with L-tryptophan.
1 to 8 grams per day (under a doctor's supervision) 2 stars[2 stars]
L-tryptophan supplementation has occasionally been helpful for specific schizophrenia symptoms, such as aggression and memory function.
Seasonal Affective Disorder
With doctor's supervision, 2 to 4 grams per day, increasing up to 6 grams if no improvement 2 stars[2 stars]
Some research suggests that L-tryptophan alone or in combination with light therapy may improve SAD symptoms.
Alcohol Withdrawal

(Glutamine, L-Tyrosine, Multivitamin, Phenylalanine)
Refer to label instructions 1 star[1 star]
In double-blind research, alcoholics treated with L-tyrosine combined with DLPA (D,L-phenylalanine), L-glutamine, prescription L-tryptophan, plus a multivitamin had reduced withdrawal symptoms and decreased stress.
Refer to label instructions 1 star[1 star]
Research suggests a connection between anxiety and serotonin deficiency and that its precursur L-tryptophan may help reduce anxiety in people with social anxiety disorder and neurosis.
Attention Deficit–Hyperactivity Disorder
Refer to label instructions 1 star[1 star]
Imbalances in the brain chemical serotonin, or low blood levels of its precursor, L-tryptophan, have been associated with ADHD in some (though not all) studies
Refer to label instructions 1 star[1 star]
L-tryptophan may be beneficial for people with bulimia, as this amino acid synthesizes serotonin, a hormone that helps regulate food intake and appetite.

(Vitamin B6)
Refer to label instructions 1 star[1 star]
Vitamin B6, when taken with L-tryptophan, has been shown to improve eating behavior, feelings about eating, and mood among women with bulimia.
3 to 4 grams per day1 star[1 star]
Supplementing with L-tryptophan can temporarily raise blood serotonin levels and lower blood pressure, but whether L-tryptophan can help prevent and manage hypertension in the long-term is still unknown.
Migraine Headache
Refer to label instructions 1 star[1 star]
Preliminary research has found abnormally low levels of serotonin in the brains of people suffering a migraine attack, which was reversed with L-tryptophan supplements.
Restless Legs Syndrome
1 to 2 grams at bedtime 1 star[1 star]
Preliminary research has shown some benefit reducing symptoms of restless legs syndrome and the insomnia that often accompanies it.
Smoking Cessation
Refer to label instructions 1 star[1 star]
In one study, tryptophan supplements along with a high-carbohydrate diet lessened withdrawal symptoms and helped people smoke fewer cigarettes.
Tardive Dyskinesia
Refer to label instructions 1 star[1 star]
Animal research and preliminary human reports suggest that L-tryptophan may help  reduce the severity of symptoms.

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The information presented by TraceGains is for informational purposes only. It is based on scientific studies (human, animal, or in vitro), clinical experience, or traditional usage as cited in each article. The results reported may not necessarily occur in all individuals. Self-treatment is not recommended for life-threatening conditions that require medical treatment under a doctor's care. For many of the conditions discussed, treatment with prescription or over the counter medication is also available. Consult your doctor, practitioner, and/or pharmacist for any health problem and before using any supplements or before making any changes in prescribed medications. Information expires December 2024.