What is it?
People use L-tryptophan for some mental health disorders, to help quit smoking, for athletic performance, and for emotional symptoms in people with premenstrual dysphoric disorder (PMDD), but there is no good scientific evidence to support many of these uses. There is also concern that using L-tryptophan might cause a condition called eosinophilia-myalgia syndrome (EMS).
How effective is it?
Natural Medicines Comprehensive Database rates effectiveness based on scientific evidence according to the following scale: Effective, Likely Effective, Possibly Effective, Possibly Ineffective, Likely Ineffective, Ineffective, and Insufficient Evidence to Rate.
The effectiveness ratings for L-TRYPTOPHAN are as follows:
Possibly effective for...
- Premenstrual dysphoric disorder (PMDD). Taking 6 grams of L-tryptophan per day seems to decrease mood swings, tension, and irritability in women with PMDD.
- To help people quit smoking. Taking L-tryptophan seems to help people quit smoking when used with conventional treatment.
Possibly ineffective for...
- Teeth grinding (bruxism). Taking L-tryptophan by mouth doesn't help treat teeth grinding.
- Facial pain. Taking L-tryptophan by mouth doesn't help reduce facial pain.
Insufficient evidence to rate effectiveness for...
- Improving athletic ability. Some research shows that taking L-tryptophan for 3 days before exercising can improve power during exercise. This improvement in power helps increase the distance an athlete can go in the same amount of time. But other early research shows that taking L-tryptophan during exercise doesn't improve endurance during a cycling exercise. Reasons for the conflicting results are not clear. It is possible that L-tryptophan improves some measures of athletic ability but not others. On the other hand, L-tryptophan might need to be taken for a few days before exercise in order to see any benefit.
- Attention deficit-hyperactivity disorder (ADHD). There is some evidence that L-tryptophan levels are lower in children with ADHD. But taking L-tryptophan supplements does not appear to improve ADHD symptoms.
- Problems with mental function in the elderly. Taking a mixture of L-tryptophan and other ingredients can slightly improve mental function in older people. But the improvement is very small, so it might not be meaningful. Also, it's not known if any potential benefit is due to L-tryptophan or another ingredient.
- Depression. Early research suggests that L-tryptophan might improve the effectiveness of common medications for depression.
- Healing ulcers caused by the bacteria Helicobacter pylori (H pylori). Research shows that taking L-tryptophan in combination with the ulcer medication omeprazole improves ulcer healing rates compared to taking omeprazole alone.
- 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.
- Seasonal affective disorder (SAD). Early research suggests L-tryptophan might be helpful in SAD.
- Treating sleep apnea. There is some evidence that taking L-tryptophan might decrease episodes in some people who periodically stop breathing during sleep (sleep apnea).
- Other conditions.
How does it work?
Are there safety concerns?
In 1990, L-tryptophan was recalled from the market due to these safety concerns. After the limitation of L-tryptophan products, the number of EMS cases dropped sharply. The exact cause of EMS in patients taking L-tryptophan is unknown, but some evidence suggests it may be due to contaminated L-tryptophan products. About 95% of all EMS cases were traced to L-tryptophan produced by a single manufacturer in Japan. Currently, under the Dietary Supplement Health and Education Act (DSHEA) of 1994, L-tryptophan is available and marketed as a dietary supplement.
L-tryptophan can cause some side effects such as heartburn, stomach pain, belching and gas, nausea, vomiting, diarrhea, and loss of appetite. It can also cause headache, lightheadedness, drowsiness, dry mouth, visual blurring, muscle weakness, and sexual problems.
Special precautions & warnings:Pregnancy and breast-feeding: L-tryptophan is LIKELY UNSAFE in pregnancy because it may harm the unborn child. Not enough is known about the safety of L-tryptophan during breast-feeding. Avoid using L-tryptophan during pregnancy and breast-feeding.
A white blood cell disorder called eosinophilia: L-tryptophan might make this condition worse. L-tryptophan has been associated with the development of eosinophilia-myalgia syndrome (EMS).
Liver or kidney disease: L-tryptophan might make these conditions worse since it has been associated with the development of eosinophilia-myalgia syndrome (EMS).
Are there interactions with medications?
- Sedative medications (CNS depressants)
- L-tryptophan might cause sleepiness and drowsiness. Medications that cause sleepiness are called sedatives. Taking L-tryptophan along with sedative medications might cause too much sleepiness.
Some sedative medications include clonazepam (Klonopin), lorazepam (Ativan), phenobarbital (Donnatal), zolpidem (Ambien), and others.
- Dextromethorphan (Robitussin DM, and others)
- L-tryptophan can affect a brain chemical called serotonin. Dextromethorphan (Robitussin DM, others) can also affect serotonin. Taking L-tryptophan along with dextromethorphan (Robitussin DM, others) might cause there to be too much serotonin in the brain and serious side effects including heart problems, shivering and anxiety could occur. Do not take L-tryptophan if you are taking dextromethorphan (Robitussin DM, others).
- Medications for depression (Antidepressant drugs)
- L-tryptophan increases a brain chemical called serotonin. Some medications for depression also increase the brain chemical serotonin. Taking L-tryptophan along with these medications for depression might increase serotonin too much and cause serious side effects including heart problems, shivering, and anxiety. Do not take L-tryptophan if you are taking medications for depression.
Some of these medications for depression include fluoxetine (Prozac), paroxetine (Paxil), sertraline (Zoloft), amitriptyline (Elavil), clomipramine (Anafranil), imipramine (Tofranil), and others.
- Medications for depression (MAOIs)
- L-tryptophan increases a chemical in the brain. This chemical is called serotonin. Some medications used for depression also increase serotonin. Taking L-tryptophan with these medications used for depression might cause there to be too much serotonin. This could cause serious side effects including heart problems, shivering, and anxiety.
Some of these medications used for depression include phenelzine (Nardil), tranylcypromine (Parnate), and others.
- Meperidine (Demerol)
- L-tryptophan increases a chemical in the brain called serotonin. Meperidine (Demerol) can also increase serotonin in the brain. Taking L-tryptophan along with meperidine (Demerol) might cause too much serotonin in the brain and serious side effects including heart problems, shivering, and anxiety.
- Pentazocine (Talwin)
- L-tryptophan increases a brain chemical called serotonin. Pentazocine (Talwin) also increases serotonin. Taking L-tryptophan along with pentazocine (Talwin) might cause serious side effects including heart problems, shivering, and anxiety. Do not take L-tryptophan if you are taking pentazocine (Talwin).
- Taking L-tryptophan with phenothiazines can cause serious side effects including movement disorders.
Some phenothiazines include chlorpromazine (Thorazine), fluphenazine (Prolixin), trifluoperazine (Stelazine), thioridazine (Mellaril), and others.
- Sedative medications (Benzodiazepines)
- Sedative medications can affect the nervous system. L-tryptophan can also affect the nervous system. Taking L-tryptophan along with sedative medications can cause serious side effects. Do not take L-tryptophan if you are taking sedative medications.
Some of these sedative medications include clonazepam (Klonopin), diazepam (Valium), lorazepam (Ativan), and others.
- Tramadol (Ultram)
- Tramadol (Ultram) can affect a chemical in the brain called serotonin. L-tryptophan can also affect serotonin. Taking L-tryptophan along with tramadol (Ultram) might cause too much serotonin in the brain and side effects including confusion, shivering, and stiff muscles could result.
Are there interactions with herbs and supplements?
- Herbs and supplements that act like sedatives
- L-tryptophan can cause drowsiness and relaxation. Using it along with other herbs and supplements that also have sedative effects might cause too much drowsiness. Some of these herbs and supplements include 5-HTP, calamus, California poppy, catnip, hops, Jamaican dogwood, kava, St. John's wort, skullcap, valerian, yerba mansa, and others.
- Herbs and supplements that increase serotonin levels
- L-tryptophan seems to raise the level of serotonin, a hormone that transmits signals between nerve cells and affects mood. There is a concern that using it with other herbs and supplements that increase serotonin, might increase the effects and side effects of those herbs and supplements. Some of those include 5-HTP, Hawaiian baby woodrose, and S-adenosylmethionine (SAMe).
- St. John's wort
- Combining L-tryptophan with St. John's wort might increase the risk of serotonin syndrome, a possibly fatal condition that occurs when there is too much serotonin in the body. There is a report of serotonin syndrome in a patient who took L-tryptophan and high doses of St. John's wort.
Are there interactions with foods?
- There are no known interactions with foods.
What dose is used?
- Premenstrual dysphoric disorder (PMDD): Doses of 6 grams of L-tryptophan have been taken daily from ovulation to the third day of the period.
- To help people quit smoking: Doses of 50 mg/kg of L-tryptophan have been taken daily.
To learn more about how this article was written, please see the Natural Medicines Comprehensive Database methodology.
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