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Complementary and Alternative Medicine - Cam

Search Health Information    L-Tryptophan

L-Tryptophan

Uses

What Are Star Ratings?

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.

3 Stars Reliable and relatively consistent scientific data showing a substantial health benefit.

2 Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.

1 Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support.

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

Used for Why
3 Stars
Insomnia
1 to 2 grams at bedtime
L-tryptophan has been used successfully for people with insomnia in many studies,including double-blind trials.
The amino acid , L-tryptophan, a serotonin precursor, taken in amounts of 1 to 4 grams at bedtime, has been used successfully for people with insomnia in many studies,2 , 3including double-blind trials.4 , 5 , 6 , 7 Some research indicates that people with more severe forms of insomnia may need to take L-tryptophan for several nights before improvement in sleep is noticed.8 , 9One controlled trial found that newborns receiving a bottle feeding in which 420 mg of L-tryptophan per 2.2 lbs of body weight had been added entered quiet sleep sooner and slept for a longer time.10 Some preliminary and controlled trials have not found L-tryptophan effective,11 or have found L-tryptophan effective only for people who awaken more frequently at night compared with those who awaken less frequently.12 Several studies combined L-tryptophan with a carbohydrate-containing meal to improve L-tryptophan uptake into the brain.13 , 14 A related compound that occurs naturally in the body, 5-HTP  is also converted into serotonin and might, therefore, be helpful for insomnia. In a double-blind study of people without insomnia, supplementation with 5-HTP (200 mg at 9:15 p.m. and 400 mg at 11:15 p.m.) increased rapid-eye-movement (REM) sleep, presumably indicating improved sleep quality.15 In a preliminary study of people with fibromyalgia , supplementing with 100 mg of 5-HTP three times a day improved sleep quality.16 However, additional research is needed to determine whether 5-HTP is safe and effective for people with insomnia.In a preliminary study, 5-HTP was also found to be an effective treatment for "sleep terrors,"17 a common problem in children that causes sudden awakening with persistent fear or terror, screaming, sweating, confusion, and increased heart rate.
3 Stars
Pain
2 to 4 grams per day
Double-blind research has also shown that oral L-tryptophan can increase tolerance to acute pain.
Other amino acids may be beneficial in reducing pain. Animal research has shown that the brain chemical serotonin is involved in pain perception,18 and some,19 , 20 though not all,21 preliminary human studies have reported reduced pain sensitivity when people took 2.0 to 2.75 grams per day of L-tryptophan, a precursor of serotonin. In a double-blind study, patients recovering from gallbladder surgery reported less pain when they were given L-tryptophan intravenously in the amount of 7.5 to 15 mg per 2.2 pounds body weight.22 Double-blind research has also shown that oral L-tryptophan can increase tolerance to acute pain when taken in amounts of at least 2 grams per day.23 , 24 Two double-blind trials found that 3 to 4 grams per day of L-tryptophan along with a low-protein, high-carbohydrate diet reduced pain in people with chronic pain.25 , 26 However, one controlled study did not find L-tryptophan (50 mg per 2.2 pounds of body weight per day) helpful for people with chronic pain around the temporomandibular joint.27 No research has been published investigating the pain control potential of 5-HTP (5-hydroxytryptophan), another serotonin precursor.
3 Stars
Premenstrual Syndrome
2 to 6 grams per day, during the second half of the menstrual cycle
Some research suggests that L-tryptophan may help balance mood symptoms associated with PMS.
Preliminary research suggests that imbalances of the neurotransmitter serotonin or its precursor, L-tryptophan, may be associated with PMS.28 In a double-blind trial, women with PMS who took 6 grams per day of L-tryptophan during the second half of their menstrual cycle reported a one-third reduction in the severity of abnormal mood symptoms.29 This confirmed the results of an earlier preliminary trial in which 2 grams per day of L-tryptophan taken during the second half of the menstrual cycle reduced depression and other symptoms associated with PMS.30
2 Stars
Depression
3 to 6 grams per day
Several controlled trials have found L-tryptophan as effective as antidepressant medications. Depressed people should consult a doctor before use.  

Disruptions in emotional well-being, including depression, have been linked to serotonin imbalances in the brain.31 L-Tryptophan is the precursor to serotonin, and low body levels of L-tryptophan are associated with depression symptoms.32 Furthermore, L-tryptophan supplements have been shown to increase serotonin levels.33  Many uncontrolled studies report that 3 to 6 grams per day of L-tryptophan helps improve mood in depressed people.34 , 35 Several controlled trials found that 3 to 6 grams per day of L-tryptophan were equally as effective as antidepressant medications.36 , 37 Some,38 , 39 , 40 though not all,41 , 42 double blind studies reported that similar amounts of L-tryptophan were superior to a placebo for improving depression symptoms. Trials using amounts above 6 grams per day of L-tryptophan have often found no benefit for depression, suggesting that 3 to 6 grams per day is optimum.43 5-Hydroxytryptophan (5-HTP), a breakdown product of L-tryptophan and a serotonin precursor, has also been studied as a treatment for depression. Some trials using 200 to 300 mg per day of 5-HTP with people suffering from depression have shown signs of efficacy.44 , 45 , 46 , 47 , 48 , 49 However, much of the research was either uncontrolled or used 5-HTP in combination with antidepressant drugs. Depressed people interested in considering 5-HTP should consult a doctor.

2 Stars
Obsessive-Compulsive Disorder
6 grams per day (only under a doctor's supervision)
With a doctor's supervision, some people with OCD have experienced some symptom relief from supplementing with L-tryptophan.
Serotonin-modifying drugs are often effective for OCD, suggesting that L-tryptophan, a precursor of serotonin, might also be effective.50 One preliminary human study reported improvement in OCD symptoms when 6 grams per day of L-tryptophan was added to therapy with a serotonin-enhancing drug.51 This treatment should be undertaken only with a doctor's supervision, because taking L-tryptophan can increase the adverse effects of serotonin-enhancing drugs. Another preliminary trial gave seven OCD patients 3 to 9 grams per day of L-tryptophan, 400 mg per day of vitamin B6, and 2 grams per day of niacin, and found considerable improvement in symptoms after one month.52 Double-blind research is needed to confirm these findings.
2 Stars
Schizophrenia
1 to 8 grams per day (under a doctor's supervision)
L-tryptophan supplementation has occasionally been helpful for specific schizophrenia symptoms, such as aggression and memory function.
Metabolism of the amino acid L-tryptophan may be abnormal in schizophrenia,53 and initially low blood levels of L-tryptophan rise when symptoms of schizophrenia improve but remain low in cases of poor recovery.54 L-tryptophan supplementation has occasionally been helpful for specific symptoms associated with schizophrenia. A small double-blind trial found that 4 to 8 grams per day of L-tryptophan reduced aggressive symptoms.55 Another double-blind trial found 1 gram per day of L-tryptophan improved memory function in schizophrenics.56 Schizoaffective disorder has features of both schizophrenia and mood disorders. A preliminary study reported that 8 grams per day of L-tryptophan improved mood symptoms in a group of patients with schizoaffective disorder, and a small, double-blind trial found that adding 9 grams per day of L-tryptophan to drug therapy was more effective for stabilizing mood in schizoaffective disorder than drug therapy plus a placebo.57 In contrast, other symptoms of schizophrenia have not responded to L-tryptophan in amounts from 1 to 20 grams per day, according to double-blind studies.58 , 59 In fact, a small preliminary study reported that schizophrenic patients on a low-tryptophan diet had improved scores on certain tests of brain function and also had small improvements in psychotic symptoms.60
2 Stars
Seasonal Affective Disorder
With doctor's supervision, 2 to 4 grams per day, increasing up to 6 grams if no improvement
Some research suggests that L-tryptophan alone or in combination with light therapy may improve SAD symptoms.
Since disturbances of serotonin metabolism may be part of the cause of SAD,61 and creating a deficiency of L-tryptophan, a precursor of serotonin, worsens symptoms of SAD,62 L-tryptophan supplementation might be helpful. One case report describes a patient with SAD who improved after taking L-tryptophan daily, 1 gram with dinner and 1 gram at bedtime.63 In a small, preliminary study, people with SAD who responded poorly or not at all to bright light therapy were given 3 grams per day of L-tryptophan for two weeks, in addition to light therapy. Nine of 14 people responded well to this combination.64 Another small preliminary study found that one of five SAD patients that did not respond to light therapy did improve after L-tryptophan supplementation in the amount of 4 grams per day, increased to 6 grams per day if no improvement occurred at the lower dose.65 A small controlled trial found that a combination of 1.5 grams of L-tryptophan, 50 mg of vitamin B6, 300 mg vitamin C, and eight ounces of fruit juice, taken three times daily, was more effective for reducing symptoms of SAD than the same combination without L-tryptophan.66 5-HTP (5-hydroxytryptophan) is a substance related to L-tryptophan that also increases serotonin production and has shown antidepressant activity.67 It may also be useful in the treatment of SAD, but there is currently no research testing this possibility.
1 Star
Anxiety
Refer to label instructions
Research suggests a connection between anxiety and serotonin deficiency and that its precursur L-tryptophan may help reduce anxiety in people with social axiety disorder and neurosis.
Animal research suggests that the brain chemical serotonin is involved in the mechanisms underlying anxiety,68 and double-blind studies have reported that creating deficiencies of L-tryptophan, a precursor of serotonin, worsens symptoms in people with anxiety disorders.69 , 70 A small double-blind trial tested a food bar containing 250 mg of L-tryptophan plus carbohydrate compared with a placebo bar containing only carbohydrate in a people diagnosed with social anxiety disorder.71 The bars were consumed one hour before doing a task designed to provoke anxiety, and anxiety was measured with two tests of heart rate changes and by ratings of anxiety by the participants. Only one of the two heart rate measures showed the L-tryptophan bar was more effective, and only slightly lower anxiety was reported when L-tryptophan was consumed.72 A double blind study in China reported that 3 grams per day of L-tryptophan improved symptoms, including anxiety, in a group of people diagnosed with “neurosis.”73 More research is needed to evaluate L-tryptophan as a treatment for anxiety disorders.
1 Star
Attention Deficit–Hyperactivity Disorder
Refer to label instructions
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
Imbalances in the brain chemical serotonin, or low blood levels of its precursor, L-tryptophan, have been associated with ADHD in some,74 though not all,75 studies.76 , 77 Preliminary human studies report that creating deficiencies in L-tryptophan worsens some symptoms of ADHD. A small double blind trial found that giving children with ADHD a daily supplement of 100 mg L-tryptophan per 2.2 pounds body weight per day for one week improved behavior according to parents’ ratings, but not teachers’ ratings.78 More studies are needed to better evaluate L-tryptophan as a treatment for ADHD.
1 Star
Bulimia
Refer to label instructions
L-tryptophan may be beneficial for people with bulimia, as this amino acid synthesizes serotonin, a hormone that helps regulate food intake and appetite.

Serotonin, a hormone that helps regulate food intake and appetite, is synthesized in the brain from the amino acid L-tryptophan. Preliminary data suggest that some people with bulimia have low serotonin levels.79 Researchers have reported that bulimic women with experimentally induced tryptophan deficiency tend to eat more and become more irritable compared to healthy women fed the same diet,80 , 81 though not all studies have demonstrated these effects.82

Weight-loss diets result in lower L-tryptophan and serotonin levels in women,83 which could theoretically trigger bingeing and purging in susceptible people. However, the benefits of L-tryptophan supplementation are unclear. One small, double-blind trial reported significant improvement in eating behavior, feelings about eating, and mood among women with bulimia who were given 1 gram of L-tryptophan and 45 mg of vitamin B6 three times per day.84 Other double-blind studies using only L-tryptophan have failed to confirm these findings.85 , 86 L-tryptophan is available by prescription only; most drug stores do not carry it, but “compounding” pharmacies do. Most cities have at least one compounding pharmacy, which prepares customized prescription medications to meet individual patient’s needs.

1 Star
Bulimia (Vitamin B6)
Refer to label instructions
Vitamin B6, when taken with L-tryptophan, has been shown to improve eating behavior, feelings about eating, and mood among women with bulimia.

People with eating disorders who restrict their food intake are at risk for multiple nutrient deficiencies, including protein, calcium , iron , riboflavin , niacin ,87 folic acid ,88 vitamin A , vitamin C ,89 and vitamin B6 ,90 and essential fatty acids.91 A general multivitamin-mineral formula can reduce the detrimental health effects of these deficiencies.

Serotonin, a hormone that helps regulate food intake and appetite, is synthesized in the brain from the amino acid L-tryptophan. Preliminary data suggest that some people with bulimia have low serotonin levels.92 Researchers have reported that bulimic women with experimentally induced tryptophan deficiency tend to eat more and become more irritable compared to healthy women fed the same diet,93 , 94 though not all studies have demonstrated these effects.95

Weight-loss diets result in lower L-tryptophan and serotonin levels in women,96 which could theoretically trigger bingeing and purging in susceptible people. However, the benefits of L-tryptophan supplementation are unclear. One small, double-blind trial reported significant improvement in eating behavior, feelings about eating, and mood among women with bulimia who were given 1 gram of L-tryptophan and 45 mg of vitamin B6 three times per day.97 Other double-blind studies using only L-tryptophan have failed to confirm these findings.98 , 99 L-tryptophan is available by prescription only; most drug stores do not carry it, but “compounding” pharmacies do. Most cities have at least one compounding pharmacy, which prepares customized prescription medications to meet individual patient’s needs.

1 Star
Hypertension
Refer to label instructions
The brain chemical serotonin may affect blood pressure regulation, and animal research suggests its precursur L-tryptophan may help prevent and manage hypertension.
The brain chemical serotonin may play a role in blood pressure regulation,108 and animal research suggests L-tryptophan, a precursor of serotonin, might be helpful in the prevention and treatment of hypertension.109 , 110 , 111 Preliminary human studies suggest that 3 to 4 grams per day of L-tryptophan can lower blood pressure in people with hypertension.112 , 113 Double blind trials are needed to confirm these promising reports.
1 Star
Migraine Headache
Refer to label instructions
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.

Interest in the effects of serotonin on the mechanisms of migraine has led to therapeutic trials using serotonin precursors such as L-tryptophan and 5-hydroxytryptophan (5-HTP).114 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.115 A small double-blind trial found that four of eight people had fewer and less intense migraines while receiving L-tryptophan (500 mg every six hours).116 Larger double-blind trials are needed to better evaluate L-tryptophan as a migraine prevention supplement.

In one study, 40 people with recurrent migraines received either 5-HTP (200 mg per day) or methysergide (a drug used to prevent migraines) for 40 days. Both compounds reduced the frequency of migraines by about 50%.117 Larger amounts of 5-HTP (600 mg per day) were also found to be as effective as medications for reducing migraine headache attacks in adults in two double-blind trials.118 , 119 Migraine attacks were reduced in frequency, severity, and duration in 90% of those taking 400 mg per day of 5-HTP in a double-blind placebo-controlled trial,120 though another trial found no benefit of 5-HTP.121 In another controlled study, 400 mg per day of DL-5-HTP (another form of 5-HTP, equivalent to 200 mg per day of 5-HTP per day led to reduced consumption of pain-killing drugs and pain scores after one to two months.122 Children who suffered from migraines and had problems sleeping had an improvement in both migraines and sleep disorders after taking 5-HTP in the amount of 20 mg for every 10 pounds of body weight in a controlled trial,123 though an earlier study showed 5-HTP had no better effect than placebo for children with migraines.124

1 Star
Obesity
Refer to label instructions
Animal research and preliminary human reports suggest that serotonin precursors such as L-tryptophan might help control appetite and promote weight loss.

Animal research and preliminary human reports suggest that serotonin precursors such as L-tryptophan or 5-HTP (5-hydroxytryptophan) might help control appetite and promote weight loss.125 , 126 In a controlled study, increasing L-tryptophan supplementation one hour before a meal from 1 gram to 2 grams to three grams resulted in progressively fewer calories and carbohydrates being consumed during the meal at the higher L-tryptophan dosages.127 While this effect might lead to weight loss over time, a small double-blind trial did not find a significant benefit from taking 1 gram of L-tryptophan before each meal as part of a six-week weight loss program.128 Weight-loss diets result in lower L-tryptophan and serotonin levels in women,129 which could theoretically trigger cravings and make dieting more difficult.130 More research is needed to determine whether L-tryptophan might improve the results of a long-term weight loss diet.

1 Star
Restless Legs Syndrome
1 to 2 grams at bedtime
Preliminary research has shown some benefit reducing symptoms of restless legs syndrome and the insomnia that often accompanies it.
Since restless legs syndrome is often accompanied by insomnia, and L-tryptophan has been helpful for promoting sleep,131 one investigator treated two patients having both restless legs syndrome and insomnia with 1 to 2 grams of L-tryptophan at bedtime.132 In both cases restless legs symptoms improved as well as insomnia. Controlled research is needed to confirm these findings.
1 Star
Smoking Cessation
Refer to label instructions
In one study, tryptophan supplements along with a high-carbohydrate diet lessened withdrawal symptoms and helped people smoke fewer cigarettes.
Nicotine addiction is thought to be caused by increased stimulation of nerve receptors for various brain chemicals, including serotonin.133 Withdrawal symptoms that accompany smoking cessation could be related to the sudden drop in nerve receptor stimulation. However, a double-blind study found that depleting blood levels of tryptophan, the precursor to serotonin, had no effect on withdrawal symptoms after five hours of smoking abstinence.134 In a controlled study, a daily tryptophan supplement (50 mg per 2.2 pounds of body weight) along with a high-carbohydrate diet (which increases brain uptake of tryptophan) was added to a smoking cessation program. While rates of complete abstinence were not significantly affected, tryptophan plus a high-carbohydrate diet lessened withdrawal symptoms and helped participants smoke fewer cigarettes.135 More research is needed to clarify whether supplementing with tryptophan or other serotonin precursors might help support smoking cessation.
1 Star
Tardive Dyskinesia
Refer to label instructions
Animal research and preliminary human reports suggest that L-tryptophan may help  reduce the severity of symptoms.

Animal research and preliminary human reports suggest that L-tryptophan may be helpful for reducing the severity of tardive dyskinesia symptoms.136 , 137 , 138 Typical supplementation has begun with 2 grams per day of L-tryptophan, increasing to as much as eight grams per day, sometimes accompanied by a low-protein, high-carbohydrate diet and 25 mg/day of niacin (nicotinic acid).139

How It Works

How to Use It

The typical Western daily diet contains 0.5-2.0 grams of L-tryptophan.140 Some authorities recommend taking L-tryptophan supplements with food or beverages high in carbohydrate and away from foods high in protein in order to improve absorption and uptake into the brain.141 , 142

Where to Find It

L-Tryptophan is found in most protein-containing foods except for gelatin.

Possible Deficiencies

Disruptions in emotional well-being, including depression and anxiety, have been linked to serotonin imbalances in the brain.143 People with fibromyalgia often have low serotonin levels in their blood.144 , 145 , 146 Supplements of L-tryptophan may increase serotonin synthesis in these cases. The cause of migraine headaches is related to abnormal serotonin function in blood vessels,147 and L-tryptophan may help correct this abnormality.

Interactions

Interactions with Supplements, Foods, & Other Compounds

“Serotonin syndrome,” a serious but uncommon condition caused by excessive amounts of serotonin, has not been reported to result from supplementation with L-tryptophan, but it can be triggered by combining L-tryptophan with drugs that increase serotonin activity (such as certain antidepressants and certain drugs used to treat migraines).148 , 149 Also, it is conceivable that L-tryptophan would increase the toxicity of St. John's wort.

Interactions with Medicines

Certain medicines interact with this supplement.

Types of interactions: Beneficial Adverse Check

Replenish Depleted Nutrients

  • Clozapine

    Some people who take clozapine become mentally depressed after taking the drug for a few weeks. Studies have shown that clozapine can reduce blood levels of the amino acid L-tryptophan, which is often deficient in people with depression .161 More controlled research is needed to determine whether the interaction is significant and whether individuals taking clozapine might benefit from supplemental L-tryptophan or 5-hydroxytryptophan (5-HTP).

  • Diclofenac

    Diclofenac causes complex changes to L-tryptophan levels in the blood,165 but the clinical implications of this are unknown. More research is needed to determine whether supplementation with L-tryptophan is a good idea for people taking diclofenac.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Reduce Side Effects

  • none

Support Medicine

  • Allopurinol

    In a preliminary study, seven of eight individuals with severe mental depression showed improvement when they took L-tryptophan and allopurinol;150 of these seven, five experienced full remission. Controlled research is necessary to determine whether this combination might be more effective for severe depression than standard treatment.

  • Amitriptyline

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .151 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.152 , 153

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Amoxapine

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .154 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.155 , 156

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Benztropine

    Akathisia is an adverse reaction to anti-psychotic drugs, where a person has an uncontrollable desire to be in constant motion. One preliminary report suggested that 4,000 mg of L-tryptophan and 25 mg niacin per day taken with benztropine enhances the treatment of akathisia.157 Controlled studies are necessary to determine whether L-tryptophan and niacin supplements might benefit most people taking benztropine who experience adverse reactions to anti-psychotic drugs.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Clomipramine

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .158 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.159 , 160

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Desipramine

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .162 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.163 , 164

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Doxepin

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .166 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.167 , 168

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Imipramine

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .169 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.170 , 171

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Lithium

    A small double-blind study found that combining 2–4 grams three times per day of L-tryptophan with lithium significantly improved symptoms in people with bipolar disorder or a mild form of schizophrenia.172 L-tryptophan is only available from doctors. It should be taken several hours before or after meals.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Nortriptyline

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .173 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.174 , 175

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Protriptyline

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .176 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.177 , 178

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Selegiline

    Both L-tryptophan and 5-HTP have been used to treat depression . One controlled study showed that taking selegiline at the same time as 5-HTP enhanced the antidepressant effect when compared with 5-HTP alone.179 Further research is needed to determine whether taking selegiline and 5-HTP together might result in unwanted side effects.

  • Trimipramine

    Combination of 6 grams per day L-tryptophan and 1,500 mg per day niacinamide (a form of vitamin B3) with imipramine has shown to be more effective than imipramine alone for people with bipolar disorder .180 These levels did not improve the effects of imipramine in people with depression . Lower amounts (4 grams per day of L-tryptophan and 1,000 mg per day of niacinamide) did show some tendency to enhance the effect of imipramine.

    The importance of the amount of L-tryptophan was confirmed in other studies, suggesting that if too much L-tryptophan (6 grams per day) is used, it is not beneficial, while levels around 4 grams per day may make tricyclic antidepressants work better.181 , 182

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Reduces Effectiveness

  • none

Potential Negative Interaction

  • Citalopram

    Citalopram increases serotonin activity in the brain. 5-HTP and L-tryptophan are converted to serotonin in the brain, and taking either of these compounds with citalopram may increase citalopram-induced side effects. Dietary supplements of L-tryptophan (available only by prescription from special compounding pharmacists) taken with paroxetine (a drug that has similar actions as citalopram) caused headache, sweating, dizziness, agitation, restlessness, nausea, vomiting, and other symptoms.183

    Some doctors have used small amounts of L-tryptophan in combination with SSRIs, to increase their effectiveness. However, because of the potential for side effects, 5-HTP and L-tryptophan should never be taken in combination with citalopram or other SSRIs, unless a doctor is closely monitoring the combination. Foods rich in L-tryptophan do not appear to interact with citalopram or other SSRIs.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Escitalopram

    Escitalopram increases serotonin activity in the brain. 5-HTP and L-tryptophan are converted to serotonin in the brain, and taking either of these compounds with escitalopram may increase escitalopram-induced side effects. Dietary supplements of L-tryptophan (available only by prescription from special compounding pharmacists) taken with paroxetine (a drug that has similar actions as escitalopram) caused headache, sweating, dizziness, agitation, restlessness, nausea, vomiting, and other symptoms.184

    Some doctors have used small amounts of L-tryptophan in combination with SSRIs, to increase their effectiveness. However, because of the potential for side effects, 5-HTP and L-tryptophan should never be taken in combination with escitalopram or other SSRIs, unless a doctor is closely monitoring the combination. Foods rich in L-tryptophan do not appear to interact with escitalopram or other SSRIs.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Fluoxetine

    L-tryptophan is an amino acid found in protein-rich foods. Foods rich in L-tryptophan are not believed to cause any problems during fluoxetine use. However, dietary supplements of L-tryptophan taken during fluoxetine treatment have been reported to cause headache, sweating, dizziness, agitation, restlessness, nausea, vomiting, and other symptoms.185

  • Fluvoxamine

    Fluvoxamine works by increasing serotonin activity in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them with fluvoxamine may increase fluvoxamine-induced side effects. Until more is known, 5-HTP and L-tryptophan should not be taken with any SSRI drug, including fluvoxamine.

  • Paroxetine

    Paroxetine increases serotonin activity in the brain. 5-HTP and L-tryptophan are converted to serotonin in the brain, and taking either of these compounds with paroxetine may increase paroxetine-induced side effects. Dietary supplements of L-tryptophan (available only by prescriptions from special compounding pharmacists) taken with paroxetine caused headache, sweating, dizziness, agitation, restlessness, nausea, vomiting, and other symptoms.186 Some doctors have used small amounts of L-tryptophan in combination with SSRIs, to increase the effectiveness of the latter. However, because of the potential for side effects, 5-HTP and L-tryptophan should never be taken in combination with paroxetine or other SSRIs, unless the combination is being closely monitored by a doctor. Foods rich in L-tryptophan do not appear to interact with paroxtine or other SSRIs.

    On the other hand, the combination of 45 mg DL-tryptophan (a synthetic variation of L-tryptophan) per pound of body weight (a relatively high dose) with zimelidine, a drug with a similar action to paroxetine, did not cause these side effects in another trial.187

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Sertraline

    Sertraline increases serotonin activity in the brain. 5-HTP and L-tryptophan are converted to serotonin in the brain, and taking either of these compounds with sertraline may increase sertraline-induced side effects.

    In one report, dietary supplements of L-tryptophan (available only by prescriptions from special compounding pharmacists) taken with paroxetine (a drug similar to sertraline) caused headache, sweating, dizziness, agitation, restlessness, nausea, vomiting, and other symptoms.188 On the other hand, the combination of 45 mg DL-tryptophan (a synthetic variation of L-tryptophan) per pound of body weight (a relatively high dose) with zimelidine, a drug with a similar action to sertraline, did not cause these side effects in another trial.189 Some doctors have used small amounts of L-tryptophan in combination with SSRIs, to increase the effectiveness of the latter. However, because of the potential for side effects, 5-HTP and L-tryptophan should never be taken in combination with sertraline or other SSRIs, unless the combination is being closely monitored by a doctor. Foods rich in L-tryptophan do not appear to interact with sertraline or other SSRIs.

  • Sibutramine

    The amino acids L-tryptophan and 5-hydroxytryptophan (5-HTP) are occasionally used to treat mental depression . Taking sibutramine with L-tryptophan or 5-HTP might result in a rare, but serious group of symptoms known as “serotonin syndrome.”190 Symptoms associated with serotonin syndrome may include confusion, anxiety, muscle weakness, incoordination, and vomiting. Therefore, individuals taking sibutramine should avoid supplementing with L-tryptophan and 5-HTP.

  • Tramadol

    Tramadol, which blocks serotonin reuptake in the brain, has been associated with two cases of serotonin syndrome.191 , 192 5-HTP and L-tryptophan are converted to serotonin in the brain. While no interactions have yet been reported with tramadol and 5-HTP or L-tryptophan, taking 5-HTP or L-tryptophan with tramadol may increase the risk of tramadol-induced side effects, including serotonin syndrome.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Venlafaxine

    Venlafaxine, a potent serotonin reuptake inhibitor, has been associated with several cases of serotonin syndrome.193 , 194 , 195 , 196 5-HTP and L-tryptophan are converted to serotonin in the brain, and taking them with venlafaxine may increase venlafaxine-induced side effects. While no interactions with venlafaxine and 5-HTP or L-tryptophan have been reported, until more is known, people taking venlafaxine are cautioned to avoid 5-HTP or L-tryptophan.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Zolpidem

    Nine cases of zolpidem-induced hallucinations associated with serotonin reuptake inhibiting antidepressants have been reported, some lasting for several hours.197 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them with zolpidem may increase zolpidem-induced hallucinations, though no interactions have yet been reported with zolpidem and 5-HTP or L-tryptophan.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.

Explanation Required

  • Almotriptan

    Triptans work by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them with eletriptan could increase eletriptan-induced side effects. However, no interactions have yet been reported with eletriptan and 5-HTP or L-tryptophan.

  • Clorazepate

    Test tube studies show that L-tryptophan and clorazepate dipotassium interact in the blood in such a way that the actions of the drug may be enhanced when high amounts of L-tryptophan are ingested.198 Controlled research is needed to determine the significance of this interaction and to investigate possible interactions between clorazepate and 5-hydroxytryptophan , a supplement related to L-tryptophan.

    The interaction is supported by preliminary, weak, fragmentary, and/or contradictory scientific evidence.
  • Eletriptan

    Eletriptan works by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them with eletriptan could increase eletriptan-induced side effects. However, no interactions have yet been reported with eletriptan and 5-HTP or L-tryptophan.

  • Frovatriptan

    Triptans work by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them at the same time as 5-HT1 agonists could increase unwanted side effects. However, at the time of this writing there are no known interactions with 5-HT1 agonists and 5-HTP or L-tryptophan.199

  • Naratriptan

    Triptans work by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them at the same time as 5-HT1 agonists could increase unwanted side effects. However, at the time of this writing there are no known interactions with 5-HT1 agonists and 5-HTP or L-tryptophan.200

  • Rizatriptan

    Triptans work by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them at the same time as 5-HT1 agonists could increase unwanted side effects. However, at the time of this writing there are no known interactions with 5-HT1 agonists and 5-HTP or L-tryptophan.201

  • Sumatriptan

    Sumatriptan works by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them with sumatriptan could increase sumatriptan-induced side effects. However, no interactions have yet been reported with sumatriptan and 5-HTP or L-tryptophan.

  • Zolmitriptan

    Zolmitriptan works by stimulating serotonin receptors in the brain. 5-HTP (5-Hydroxytryptophan) and L-tryptophan are converted to serotonin in the brain, and taking them with zolmitriptan could increase zolmitriptan-induced side effects. However, no interactions have yet been reported with zolmitriptan and 5-HTP or L-tryptophan.

The Drug-Nutrient Interactions table may not include every possible interaction. Taking medicines with meals, on an empty stomach, or with alcohol may influence their effects. For details, refer to the manufacturers’ package information as these are not covered in this table. If you take medications, always discuss the potential risks and benefits of adding a supplement with your doctor or pharmacist.

Side Effects

Side Effects

According to reports from clinical trials, most people tolerate L-tryptophan supplements without side effects. Occasionally, dizziness, stomach pain, and diarrhea have been reported.202

Until 1989, L-tryptophan was a popular nutritional supplement used for a variety of conditions.203 In that year, the US Food and Drug Administration removed L-tryptophan from the over-the-counter supplement market, citing the outbreak of an unusual ailment called eosinophilia-myalgia syndrome (EMS) that was associated with its use.204 Since then, researchers have determined that the most likely cause of this syndrome was a contaminant produced by a single manufacturer during the process of L-tryptophan production that was not effectively removed.205 , 206 Contamination errors have long since been corrected, and today L-tryptophan is again available as a supplement.

Two case reports suggested that a supplement containing L-tryptophan might have caused a scleroderma-like syndrome that resembled EMS in some ways.207 , 208 However, the supplement in one case contained a very small amount of L-tryptophan, and it also contained other ingredients.209 Larger surveys of people with scleroderma have found no link with L-tryptophan supplementation,210 , 211 so it is likely that these two cases were either a coincidence or it could be a contamination issue. 

The safety of taking L-tryptophan during pregnancy and breast-feeding is unclear. In a double-blind trial, the breathing activity of fetuses was temporarily altered when pregnant women took one gram of L-tryptophan.212 The relevance of that change to fetal health needs further study. In hamsters, supplementation with L-tryptophan during pregnancy decreased the litter size and increased the mortality of the offspring.213

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