L-tryptophan is an amino acid. Amino acids are protein building blocks. L-tryptophan is called an "essential" amino acid because the body can't make it on its own. It must be acquired from food.

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.


Is a Form of:

Amino acid

Primary Functions:

PMS symptoms

Also Known As:

L-Triptofano, L-Trypt, L-2-amino-3-(indole-3-yl) propionic acid, L-Tryptophane, Tryptophan

How Does It Work?

L-tryptophan is naturally found in animal and plant proteins. L-tryptophan is considered an essential amino acid because our bodies can't make it. It is important for the development and functioning of many organs in the body. After absorbing L-tryptophan from food, our bodies convert it to 5-HTP (5-hyrdoxytryptophan), and then to serotonin, melatonin, and vitamin B6 (nicotinamide). Serotonin is a hormone that transmits signals between nerve cells. It also causes blood vessels to narrow. Changes in the level of serotonin in the brain can alter mood. Melatonin is important for sleep and vitamin B6 is essential for energy metabolism.


  • 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.

Recommended Dosing

The following doses have been studied in scientific research:



  • 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.

L-Tryptophan Supplements Frequently Asked Questions

Is L Tryptophan safe to take?

When taken by mouth: L-tryptophan is POSSIBLY SAFE when taken by mouth, short-term. L-tryptophan can cause some side effects such as heartburn, stomach pain, belching and gas, nausea, vomiting, diarrhea, and loss of appetite.

Why was l tryptophan banned?

Eosinophilia–myalgia syndrome

After preliminary investigation revealed that the outbreak was linked to intake of tryptophan, the U.S. Food and Drug Administration (FDA) recalled tryptophan supplements in 1989 and banned most public sales in 1990, with other countries following suit.

How many mg of L Tryptophan should I take?

Adults: Take 8 to 12 grams of L-tryptophan by mouth per day. L-tryptophan should be taken in divided doses of three or four times a day. Pediatric: Safe and effective use in pediatric patients is not determined.

Is tryptophan good for anxiety?

Tryptophan, Mood, and Anxiety

As the availability of serotonin depends on the intake of tryptophan, dietary sources of this amino acid are seen as essential for good mental health and well-being. However, study results are mixed regarding the effects of tryptophan levels on mood and anxiety.

Does Tryptophan have side effects?

Side Effects & Safety

It can also cause headache, lightheadedness, drowsiness, dry mouth, visual blurring, muscle weakness, and sexual problems in some people. In 1989, L-tryptophan was linked to over 1500 reports of eosinophilia-myalgia syndrome (EMS) and 37 deaths.

How long does it take for L tryptophan to work?

How long does Tryptophan Take to Work? Tryptophan works within 30 minutes of ingestion, however the impact of tryptophan is regulated by conversion into 5-HTP by the body.

Does Tryptophan cause weight gain?

Since it is an essential amino acid, tryptophan deficiency may cause symptoms mirror those of protein deficiency. These include weight loss and impaired growth in infants and children. Other associated symptoms include carbohydrate cravings, overeating and weight gain.

Can you take too much L Tryptophan?

Although tryptophan is found in protein-containing foods, it's often taken as a supplement. It is likely safe at moderate doses. However, occasional side effects may occur. These side effects could become more serious if you're also taking medication that influences your serotonin levels, such as antidepressants.

Does L Tryptophan increase serotonin?

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.

Which is better for sleep L tryptophan or 5 HTP?

The amino acids 5-hydroxytryptophan (5-HTP) and l-tryptophan are precursors of serotonin. 5-HTP is generally recommended over l-tryptophan because it crosses the blood-brain barrier at a higher rate, is converted into serotonin more efficiently than l-tryptophan, and has a more pronounced antidepressant effect.

How much tryptophan should I take for anxiety?

Doses of 0.5–5 mg per day have been used, with 2 mg being the most common dose. For those who take tryptophan itself, doses of up to 5 grams per day have been reported.

Can you take L tryptophan during the day?

Our plan for the Eternus formulation was that it would be dosed during the day (ideally at breakfast). But, L-tryptophan isn't only used as a niacin equivalent in the body.

Is tryptophan an antidepressant?

Tryptophan. Tryptophan, an amino acid, is a precursor of serotonin and has been used since the 1970s to increase brain levels of serotonin. Before it was temporarily banned by the FDA (from 1989-2002), tryptophan was successfully used to supplement standard tricyclic antidepressants.

Can you take 5htp everyday?

These are all conditions that can be improved naturally through an increase in serotonin. According to one study, taking a 5-HTP supplement of 50 to 300 milligrams every day might improve symptoms of depression, binge eating, chronic headaches, and insomnia.

Can Tryptophan make you depressed?

Summary Research has shown that low levels of tryptophan may contribute to mood disorders, including depression and anxiety.

Does Tryptophan help you lose weight?

Excessive intake of sugars and other carbohydrates is known to increase brain serotonin levels. By increasing serotonin levels, tryptophan can function as an appetite suppressant at low doses, and is sometimes very effective for weight loss. As well, tryptophan has been successfully used as a sleep aid.

What time of day should I take tryptophan?

Tryptophan (TRP) is an essential amino acid, and it has been suggested that TRP intake at breakfast combined with daytime bright light exposure can increase nocturnal melatonin secretion.

Does L tryptophan help you sleep?

Supplementing with L-tryptophan helps improve sleep because it increases melatonin and serotonin, which work in harmony to regulate a person's sleep-wake cycle. The research also showed that L-tryptophan decreased sleeplessness during the night and reduced sleep latency — the amount of time it takes to fall asleep.

Does L Tryptophan make you sleepy?

Tryptophan, after all, makes you sleepy. Serotonin is a precursor to melatonin, a hormone that helps regulate sleep.” “Science has shown that L-tryptophan in doses of 1 g or more produces an increase in rated subjective sleepiness and a decrease in the amount of time it takes you to get to sleep,” explains Glassman.

What is the difference between tryptophan and L Tryptophan?

There are two types of tryptophan: L-tryptophan and D-tryptophan. The only difference between the two types is the orientation of the molecule. You can get tryptophan through certain foods or a supplement in powder form.

Does Tryptophan raise blood pressure?

The effects of L-tryptophan on blood pressure and brain serotonin have been investigated in normotensive and spontaneously hypertensive rats. The lower doses of L-tryptophan also increased blood pressure in hypertensive rats but, in contrast, the highest dose (100 mg/kg) lowered blood pressure by 30 to 35 mm Hg.

Should L Tryptophan be taken on an empty stomach?

L-Tryptophan competes with other amino acids for intestinal absorption and for uptake into the brain. L-tryptophan is most effective when taken on an empty stomach along with some carbohydrate (such as a small glass of orange juice or a piece of fruit).

Is L Tryptophan the same as 5 HTP?

5-hydroxytryptophan (5-HTP) is a chemical that the body makes from L-tryptophan. After tryptophan is converted into 5-HTP, it is then changed into serotonin. 5-HTP dietary supplements help raise serotonin levels in the brain.

Clinical Studies