Last updated: August 15, 2021

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To start the day well, our sleep quality plays an important role. A long and uninterrupted REM phase allows us to complete our tasks more efficiently the next day and our mood does not sink into the basement so quickly. L-tryptophan is an amino acid responsible for the synthesis of the "happiness hormone" serotonin. Without this hormone, we might have trouble falling asleep and it is also directly linked to our mood.

In this article, we have written together the most important scientific information for you so that you can learn more about this relevant amino acid and make the best possible decision when making your purchase.

The most important facts

  • L-tryptophan is a key element for our mental as well as physical health. This amino acid supports the synthesis of many substances that sustain our bodies. We find these ingredients in protein-rich foods.
  • Over time, this amino acid has been studied and analysed. Many results indicate that taking L-tryptophan can improve sleep quality and mood.
  • In the literature and in scientific papers, L-tryptophan is also written without L, because the other form (D-tryptophan) is often of little importance.

The Best L-Tryptophan: Our Picks

Guide: Questions you should ask yourself before buying L-tryptophan

What is L-tryptophan?

L-tryptophan was discovered at the beginning of the 20th century and it is one of the amino acids that our body cannot produce itself, so it is taken in through the diet. Together with tyrosine, histidine and phenylalanine, it forms the group of aromatic amino acids. Furthermore, L-tryptophan is one of the proteinogenic amino acids, which means they are needed for protein synthesis in our body.

It plays an important role in many metabolic processes. Some of these are:

  • Melatonin synthesis: This influences your sleep rhythm as well as your digestive processes and gastrointestinal motility.
  • Serotonin synthesis: Even though only 1% of the ingested L-tryptophan is destined for our brains, it has a strong effect on our psychiatric state and psychological processes.
  • Tryptamine synthesis: serves to control the balance between excitatory and inhibitory functions of serotonin (1).

What are the effects of L-tryptophan?

Since the discovery of L-tryptophan, many of its effects on our body have been studied and found. Its sleep-inducing effect was investigated in a 1979 study. The researchers discovered that taking 1 gram of L-tryptophan shortened the time it took to fall asleep and that taking ¼ gram extended the deep sleep phase (2).

With L-tryptophan you can also determine your own sleep rhythm, because it can effectively promote sleep phases even if they do not coincide with your biological rhythm (3). For people suffering from Obstructive Sleep Apnoea Syndrome (OSAS), taking L-tryptophan has also shown positive effects. The breathing disorders were alleviated and thus their REM phase was prolonged and their REM latency reduced (4).

For women suffering from PMS, a dinner high in L-tryptophan and carbohydrates relieved their pain, depression, anger and fatigue the next day. In comparison, the other group had only a high-carbohydrate dinner where the changes did not show up (5). Because of its role in serotonin synthesis, L-tryptophan has also been linked to promoting a better mood.

It is also claimed by some that L-tryptophan helps with weight loss. This effect has not been adequately studied. The results of many studies yielded contradictory results. In the study published in the "Journal of Obesity Studies", the weight loss of the overweight subjects was not significant enough to directly link this decrease to the intake of L-tryptophan (6).

This statement could have spread because serotonin receptors block the craving for carbohydrates, which can subsequently lead to weight loss. However, it must be taken into account that with a high-protein and low-carbohydrate meal, the body supplies itself with other amino acids that compete with L-tryptophan. So the brain is supplied with less L-tryptophan and therefore less serotonin is produced (7).

Why is L-tryptophan important?

Without this amino acid, the creation of the "happiness hormone" serotonin would not take place. Even though serotonin does not focus only on a specific function in our brain, this hormone is responsible for food intake, activity rhythm, sexual behaviour and emotional states (8).


Serotonin also plays an important role in memory and learning
(Image source: / Helena Lopes)

In addition, L-tryptophan is necessary for the "sleep hormone" melatonin and for the synthesis of nicotinic acid.

Nicotinic acid is involved in the activation of all the enzymes found in our body and thus it regulates many processes that should happen in our body (1).

What is the right dosage of L-tryptophan?

When determining the correct dosage of this amino acid, age, weight, body type, exercise, diet, stress and health status are criteria that should be taken into account. Apart from this, the L-tryptophan requirement of an average adult could be estimated and this value is between 3.5 and 6 milligrams per body weight per day and depends on the type of source (9)

It has been calculated that we normally consume between 0.5 to 2 grams of L-tryptophan per day through a healthy diet and even this small amount improves our sleep quality. The quality of our deep sleep will be improved by the intake of only 1/4 gram (250 milligrams) (10)

To improve and prolong the REM phase for people who have sleep disordered breathing (OSAS), taking 2.5 grams of L-tryptophan, preferably before bedtime, is sufficient (11)

When taking L-tryptophan and additionally 5-HTP (5 hydroxy tryptophan), the dosage should be reduced.

Since both amino acids cause an increase in serotonin levels, this combination can lead to an excess of serotonin in the brain, which can have negative effects (12).

What are the possible side effects of L-tryptophan?

On the market, some manufacturers offer L-tryptophan together with 5-HTP. You should never exceed the daily amount, because an excess of serotonin can cause nausea, dizziness, dizziness and excessive sweating.

There are no side effects if you only get your L-tryptophan intake from food.

No side effects have been found for breastfeeding women either. In 2015, a study published in the Journal of European Neuropsychopharmacology showed that L-tryptophan supplements maintain normal L-tryptophan levels in breast milk. Therefore, there is no danger for the baby (13).

For pregnant women, however, it has not yet been established whether taking L-tryptophan supplements is safe. So it is best to talk to your doctor first or not to take L-tryptophan supplements.

Who should take L-tryptophan supplements?

In a healthy balanced diet we already supply our body with enough L-tryptophan. However, there are factors that impair the absorption of this amino acid. One group of people who have trouble absorbing L-tryptophan are those who suffer from fructose malabsorption (14).


The quality of our bedtime affects our ability to learn, memory and mood. One reason why you should not neglect it.
(Image source: / Kinga Cichewicz)

People who want to improve their sleep patterns can also take L-tryptophan supplements. Better sleep quality affects mood and moodiness. The length and quality of sleep have been linked to the maintenance of a positive mood (15). Pregnant women should avoid L-tryptophan supplements for the time being, because their effects on the baby have not yet been classified as "safe".

Decision: What types of L-tryptophan are there and which is right for you?

With L-tryptophan intake coming exclusively from food, there will usually be no overdose. But for people who need a higher concentration of this amino acid, the following options are on the market. The next few lines should help you make the best decision.

What distinguishes L-tryptophan in capsules and what are its advantages and disadvantages?

When taking the L-tryptophan amino acid in capsules, the substance is better absorbed by our bodies.

  • Easy to transport
  • Robust packaging
  • Easy dosage without having to weigh
  • Sufficient liquid is necessary when taking the capsules

What are the advantages and disadvantages of powdered L-tryptophan?

When taking powder, it is also possible to mix it with yoghurt or muesli.

  • Easy to transport
  • dosage can be adjusted
  • Packaging can be torn
  • sufficient liquid is necessary when taking

What distinguishes L-tryptophan as an oral spray and what are its advantages and disadvantages?

You often need to shake it well before use so that the other ingredients are well mixed. The mouth spray works faster than another dosage form. The sprayed substance comes into contact with your oral mucosa immediately, which means there is no digestion process and the substance enters your bloodstream immediately.

  • Space-saving packaging
  • Works much faster than powder or capsule
  • For sleeping only
  • Not much choice on the market

Buying criteria: These are the factors you can use to compare and evaluate L-tryptophan

Since this ingredient improves important functions of our body, you can find it on the market in various forms.


If you are stressed about work or university and find it difficult to fall asleep, you can use the capsules, powder or oral spray. All three forms will improve the quality of your sleep. One important difference is that the mouth spray works faster because it doesn't have to be digested first like the other forms.


Since the correct dosage depends greatly on your body composition, age and weight, it is not the same for everyone. If you decide to take the powder, you can calculate it yourself and take the exact amount. With capsules, the daily requirement is already determined and you are therefore less flexible with the dosage.

Dosage form

All three options have their advantages and disadvantages, which have already been explained above. Only your opinion is important here. Some people don't get on with the capsules and for others it's no problem. So just choose the option that suits you best.

Facts worth knowing about L-tryptophan

Which foods contain L-tryptophan?

L-tryptophan is one of the amino acids that can be supplied by certain foods or preparations, because our body cannot produce it itself. Certain foods have higher levels of L-tryptophan and we have listed these for you in a table with their corresponding concentration.

Food L-tryptophan (mg) content per 100 grams
bran 250
oatmeal 190
millet 180
lima beans 300
soya beans 450
tuna 300
mackerel 270
salmon 260
pork liver 310
pork 300
ham 294

(source: vitalstoff-lexikon. de).de) (16).

Fruits and vegetables usually contain little L-tryptophan. Some vegetables with higher L-tryptophan are kale with 64 mg and chanterelles with 48 mg.

When is the best time to take L-tryptophan?

The manufacturers of L-tryptophan supplements have a recommendation written on the packaging or their website. They usually recommend taking the supplements or capsules 30 minutes or just before bedtime.

Image source: Piotrkt/

References (16)

1. Autoren: Dawn M Richard, Michael A Dawes, Charles W Mathias, Ashley Acheson, Nathalie Hill-Kapturczak, and Donald M Dougherty

2. Autor: Hartmann E, Spinweber CL.

3. Autor: Schmidt HS.

4. Autor: Schmidt HS.

5. Autor: Wurtman JJ, Brzezinski A, Wurtman RJ, Laferrere B.

6. Autor: Strain GW, Strain JJ, Zumoff B.

7. Autor: Wurtman RJ, Wurtman JJ.

8. Autor: Buhot MC, Martin, S.

9. Autor: United Nations University

10. Autor: Hartmann E, Spinweber CL.

11. Autor: Schmidt HS.

12. Autor: Volpie-Abadie, J., Kaye A.

13. Autor: Dowlati Y, Ravindran AV, Maheux M, Steiner M, Stewart DE, Meyer JH.

14. Autor: Ledochowski M, Widner B, Propst-Braunsteiner T, Vogel W, Sperner-Unterweger B, Fuchs D.

15. Autor: Silber BY1, Schmitt JA.

16. Autor: Doc Medicus

Why you can trust me?

L-Tryptophan: Basic Metabolic Functions, Behavioral Research and Therapeutic Indications
Autoren: Dawn M Richard, Michael A Dawes, Charles W Mathias, Ashley Acheson, Nathalie Hill-Kapturczak, and Donald M Dougherty
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Sleep induced by L-tryptophan. Effect of dosages within the normal dietary intake
Autor: Hartmann E, Spinweber CL.
Go to source
L-tryptophan: effects on daytime sleep latency and the waking EEG.
Autor: Schmidt HS.
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L-tryptophan in the treatment of impaired respiration in sleep
Autor: Schmidt HS.
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Effect of nutrient intake on premenstrual depression
Autor: Wurtman JJ, Brzezinski A, Wurtman RJ, Laferrere B.
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L-tryptophan does not increase weight loss in carbohydrate-craving obese subjects
Autor: Strain GW, Strain JJ, Zumoff B.
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Carbohydrate craving, obesity and brain serotonin
Autor: Wurtman RJ, Wurtman JJ.
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Role of serotonin in memory impairment
Autor: Buhot MC, Martin, S.
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Recent 24-hour tracer studies of amino acid requirements
Autor: United Nations University
Go to source
Sleep induced by L-tryptophan. Effect of dosages within the normal dietary intake.
Autor: Hartmann E, Spinweber CL.
Go to source
L-tryptophan in the treatment of impaired respiration in sleep.
Autor: Schmidt HS.
Go to source
Serotonin Syndrome
Autor: Volpie-Abadie, J., Kaye A.
Go to source
No effect of oral L-tryptophan or alpha-lactalbumin on total tryptophan levels in breast milk.
Autor: Dowlati Y, Ravindran AV, Maheux M, Steiner M, Stewart DE, Meyer JH.
Go to source
Fructose malabsorption is associated with decreased plasma tryptophan
Autor: Ledochowski M, Widner B, Propst-Braunsteiner T, Vogel W, Sperner-Unterweger B, Fuchs D.
Go to source
Effects of tryptophan loading on human cognition, mood, and sleep.
Autor: Silber BY1, Schmitt JA.
Go to source
Tryptophan-Gehalt – angegeben in mg – pro 100 g Lebensmittel
Autor: Doc Medicus
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