What is it?
People use L-tryptophan for severe PMS symptoms (premenstrual dysphoric disorder or PMDD) and quitting smoking. It is also used for athletic performance, depression, insomnia, and many other conditions, but there is no good scientific evidence to support many of these uses.
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...
- Severe PMS symptoms (premenstrual dysphoric disorder or PMDD). Taking 6 grams of L-tryptophan per day seems to decrease mood swings, tension, and irritability in women with PMDD.
- Quitting 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.
- A condition that causes persistent muscle pain (myofascial pain syndrome). Taking L-tryptophan by mouth doesn't help reduce persistent muscle pain.
Insufficient evidence to rate effectiveness for...
- Athletic performance. 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.
- Depression. Early research suggests that L-tryptophan might improve the effectiveness of common medications for depression.
- A digestive tract infection that can lead to ulcers (Helicobacter pylori or H. pylori). Research shows that taking L-tryptophan in combination with the ulcer medication omeprazole improves ulcer healing rates compared to taking omeprazole alone.
- Insomnia. Taking L-tryptophan might decrease the amount of time it takes to fall asleep and improve mood in healthy people with sleep problems. Taking L-tryptophan might also improve sleep in people with sleep problems related to withdrawal of illegal drugs.
- Seasonal depression (seasonal affective disorder or SAD). Early research suggests L-tryptophan might be helpful in SAD.
- A sleep disorder in which people temporarily stop breathing while asleep (sleep apnea). There is some evidence that taking L-tryptophan might decrease episodes in some people who periodically stop breathing during sleep (sleep apnea).
- Decline in memory and thinking skills in older people that is more than what is normal for their age.
- Premenstrual syndrome (PMS).
- Tourette syndrome.
- Other conditions.
How does it work?
Are there safety concerns?
There isn't enough reliable information to know if L-tryptophan is safe when taken by mouth long-term.
Special precautions & warnings:Pregnancy and breast-feeding: L-tryptophan is LIKELY UNSAFE in pregnancy because it may harm the unborn child. There isn't enough reliable information to know if L-tryptophan is safe to use when breast-feeding. Stay on the safe side and avoid L-tryptophan during pregnancy and breast-feeding.
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 with sedative properties
- 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 with serotonergic properties
- 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?
- For severe PMS symptoms (premenstrual dysphoric disorder or PMDD): 6 grams of L-tryptophan have been taken daily from ovulation to the third day of the period.
- For quitting smoking: 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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