Tryptophan: Food Sources, Serotonin and Supplements
Tryptophan is an essential amino acid the body uses to make serotonin. Food sources, what sleep and mood trials found, the 1989 contamination episode and serotonin syndrome cautions.
Content last updated . This page has not been medically reviewed.
What is Tryptophan good for?
What the body uses it for, and how strong the evidence is. A normal job in the body is not proof that extra supplements add benefit; each card says which.
Protein building block
Established roleTryptophan is an essential amino acid: the body cannot make it, so it must come from food. Amino acids join to form proteins.
Supplements: Normal dietary intake meets this role; the sources read show no extra benefit from supplements in well-fed people.
Starting material for serotonin
Established roleThe body uses tryptophan to make serotonin, a chemical messenger linked to mood.
Supplements: Being a precursor does not mean extra tryptophan raises serotonin or mood; trials are summarized below.
Time awake after falling asleep
Preliminary or mixedA 2022 analysis of four studies found tryptophan shortened time awake after falling asleep, mostly at 1 g a day or more; other sleep measures did not change.
Supplements: Few small studies; not proof it treats insomnia.
Mood in healthy adults
Preliminary or mixedIn a review of 11 trials in healthy adults, four found better mood or less negative feeling than the comparison group; aggressive feelings were not affected.
Supplements: Mixed results in healthy people; says nothing about treating depression.
Feelings of anxiety
Preliminary or mixedThe same review suggested tryptophan may reduce anxious feeling in healthy individuals.
Supplements: Limited and mixed; the review authors called for more studies.
Treatment of depression
Not enough evidenceThe review read tested healthy adults, not people being treated for depression, so no claim is made.
Supplements: Insufficient evidence from the sources read.
Connected topics
Open a group to see how each topic connects and how strong the evidence is.
Health goals (4)
- Anxiety SupportPreliminary or mixed
In the same review of healthy adults, some trials found less anxious feeling. Evidence is limited and mixed; it does not show treatment of an anxiety disorder.
- Better SleepPreliminary or mixed
Four small trials pooled in a 2022 analysis found fewer minutes awake after first falling asleep, mostly at the higher amounts studied; other sleep measures did not change. This is not proof it treats insomnia.
- Mood BalancePreliminary or mixed
A review of 11 trials in healthy adults found four with better mood or less negative feeling than the comparison group. Results are mixed and say nothing about treating depression.
- Sleep QualityPreliminary or mixed
Four small trials pooled in a 2022 analysis found fewer minutes awake after first falling asleep, mostly at the higher amounts studied; other sleep measures did not change. This is not proof it treats insomnia.
Body systems (2)
- Sleep & RecoveryPreliminary or mixed
Four small trials pooled in a 2022 analysis found fewer minutes awake after first falling asleep, mostly at the higher amounts studied; other sleep measures did not change. This is not proof it treats insomnia.
- Stress & MoodPreliminary or mixed
A review of 11 trials in healthy adults found four with better mood or less negative feeling than the comparison group. Results are mixed and say nothing about treating depression.
Body parts (1)
- CellsEstablished role
Tryptophan is one of nine essential amino acids; amino acids are the building blocks of proteins, so the body needs it from food.
Functional actions (2)
- Mood SupportPreliminary or mixed
A review of 11 trials in healthy adults found four with better mood or less negative feeling than the comparison group. Results are mixed and say nothing about treating depression.
- Sleep RegulationPreliminary or mixed
Four small trials pooled in a 2022 analysis found fewer minutes awake after first falling asleep, mostly at the higher amounts studied; other sleep measures did not change. This is not proof it treats insomnia.
Habits (1)
- Balanced NutritionEstablished role
Tryptophan cannot be made by the body, so it must come from protein foods.
Conditions & symptoms (1)
- Eosinophilia-Myalgia Syndrome, L-Tryptophan-RelatedDocumented risk
An outbreak of this rare inflammatory condition in 1989 was reported in people using L-tryptophan supplements. Whether impurities in the product or the tryptophan itself were responsible is not settled in the 2023 review read.
Documented risks and interactions (1)
- Contamination history (eosinophilia-myalgia syndrome). L-tryptophan supplements were taken off the market in 1989 after an outbreak of this rare inflammatory condition.
Urgent first
Serotonin syndrome is a potentially life-threatening reaction in which the body has too much serotonin. [1] Symptoms can include agitation, fast heartbeat, high body temperature, heavy sweating, tremor, loss of coordination and confusion. [1] Call 911 (US) or your local emergency number if these appear after starting or changing a medicine or supplement that affects serotonin. If you take an antidepressant, do not stop it on your own; talk to your health care provider first. [1]Overview
Tryptophan is one of the nine essential amino acids: the body cannot make it, so it must come from food. [2] It is also the starting material for serotonin, a chemical messenger linked to mood. [3] Being a starting material does not mean that taking more automatically raises serotonin or lifts mood; the trials below show what has actually been tested. For the other eight, see essential amino acids.Food sources
Amino acids come from animal foods such as meat, milk, fish and eggs and from plant foods such as soy, beans, legumes, nut butters and some grains. [4] A food-composition review found that tryptophan, along with lysine, methionine and threonine, generally occurs in low amounts in plant products and is enriched in animal products. [5] Per-food tryptophan amounts were not read for this page, so none are given. Health Canada's food-protein scoring pattern (for people aged 1 year and over) lists tryptophan at 7 mg per gram of protein, the smallest figure among the nine; this is a yardstick for judging food protein, not a daily target. [6]Evidence by use
Evidence labels: evidence in adequately nourished people (trials in healthy people), mixed, promising but limited, insufficient evidence.| Use | What the sources found | Evidence label |
|---|---|---|
| Sleep | A 2022 meta-analysis pooled data from four articles: tryptophan shortened time awake after falling asleep, with a larger effect at 1 g or more a day than below 1 g, but it did not affect other sleep components. [7] | Promising but limited (few trials) |
| Mood and anxiety in healthy adults | A systematic review of 11 randomized trials found four with differences in negative or happy feelings versus control; aggressive feelings were not affected. The authors concluded 0.14 to 3 g a day on top of usual meals could be expected to improve mood in healthy individuals. [3] These are study amounts, not advice. | Mixed |
| Depression treatment | Proper evidence not found: the review we read tested healthy adults, not people being treated for depression (searched PubMed for tryptophan and depression reviews). | Insufficient evidence |
| "Turkey makes you sleepy" | Not tested in the sources we read, so no claim is made. | Marketing claim / not assessed |
The sleep result is a change in minutes awake in a few small studies, not proof that tryptophan treats insomnia. If sleep problems last, see sleep supplements and natural aids, amino acids for sleep, anxiety and depression and sleep safety and when to get help.
Official intake figures and amounts
No daily requirement for tryptophan from NIH ODS, EFSA, the NHS, MedlinePlus or Health Canada could be verified, so none is quoted. A 2023 review notes that national health agencies have not set upper intake levels for amino acids because of a lack of well-conducted human dose-response trials; researchers working under a nonprofit amino acid science council proposed 4.5 g a day for relatively healthy adults. [8] That is a research proposal, not an official limit, and it says nothing about people with other conditions or on medicines.5-HTP and tryptophan are different
5-HTP (5-hydroxytryptophan) is the immediate precursor of serotonin and is sold separately. A 2004 review said no definitive cases of toxicity had emerged despite about 20 years of worldwide use, with one unresolved possible exception, and that it had been under vigilance because of its relationship to tryptophan. [9] That review dates from 2004; read the full 5-HTP guide. Do not assume findings for one transfer to the other.Frequently asked questions
Is tryptophan an essential amino acid?
Yes. The body cannot make it. [2]
Does tryptophan help you sleep?
A small meta-analysis found fewer minutes awake after falling asleep, mainly at 1 g a day or more, with no effect on other sleep components. [7]
Does eating turkey make you sleepy?
The sources read here did not test this idea, so no claim is made.
Can I take tryptophan with antidepressants?
Ask your prescriber or pharmacist first, and do not stop an antidepressant on your own. Serotonin syndrome is a risk when serotonin-affecting medicines are combined. [1]
Why were tryptophan supplements taken off the market in 1989?
An outbreak of eosinophilia-myalgia syndrome was traced to a contaminated product from a single manufacturer. [9]
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety: contamination history
Medicine interactions
Pregnancy, children, kidney and liver conditions, surgery
References
- MedlinePlus. Serotonin syndrome. National Library of Medicine, US. Read 2026-10-22.
- MedlinePlus. Amino acids. National Library of Medicine, US. Review date 1/21/2025. Read 2026-10-22.
- Kikuchi AM et al. A systematic review of the effect of L-tryptophan supplementation on mood and emotional functioning. J Diet Suppl. 2021. Read 2026-10-22.
- MedlinePlus. Protein in diet. National Library of Medicine, US. Read 2026-10-22.
- Li P, He W, Wu G. Composition of amino acids in foodstuffs for humans and animals. Adv Exp Med Biol. 2021. Read 2026-10-22.
- Health Canada. Dietary reference intakes tables: Reference values for macronutrients. Government of Canada, page dated 2025-11-19. Read 2026-10-22 through a web-fetch tool that summarised the page; rows as reported by that tool.
- Sutanto CN et al. The impact of tryptophan supplementation on sleep quality: a systematic review, meta-analysis, and meta-regression. Nutr Rev. 2022. Read 2026-10-22.
- Elango R. Tolerable upper intake level for individual amino acids in humans: a narrative review of recent clinical studies. Adv Nutr. 2023. Read 2026-10-22.
- Das YT et al. Safety of 5-hydroxy-L-tryptophan. Toxicol Lett. 2004. Read 2026-10-22.
- Ko SM et al. Safety concerns regarding impurities in L-tryptophan associated with eosinophilia myalgia syndrome. Food Chem Toxicol. 2023. Read 2026-10-22.