Tryptophan
Research reviewed: Up until 03/2026
Tryptophan (L-Tryptophan) is a dietary supplement with 10 published peer-reviewed studies involving 790 participants, researched for Sleep Quality, Depression & Mood, Anxiety & Aggression and 1 more areas.
Evidence at a Glance
Strength is scored by study design, sample size, study type, and outcomes
Sleep Quality
StrongDepression & Mood
ModerateAnxiety & Aggression
StrongAppetite & Weight
ModerateResearch Visualised
Visual breakdown of the clinical data.
Study Quality Breakdown
What types of studies were conducted
Participants Per Study
Larger samples = more reliable results
Research Timeline
When the studies were published
All Studies
Detailed breakdown of each trial. Click to expand.
Sleep Quality
To evaluate L-tryptophan on sleep quality in healthy adults with mild insomnia
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate L-tryptophan on sleep quality in healthy adults with mild insomnia
Dose
1000 mg L-tryptophan before bed
Participants
20 healthy adults with sleep difficulties
Duration
3 weeks
Results
Significant reduction in sleep latency (-10 min, p=0.02) and improvement in total sleep time. REM sleep amount increased. Well tolerated.
How They Measured It
PSG, sleep diary, Stanford Sleepiness Scale
To assess L-tryptophan on sleep quality and mood in patients with depression
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess L-tryptophan on sleep quality and mood in patients with depression
Dose
3000 mg/day L-tryptophan
Participants
50 depressed patients with insomnia
Duration
4 weeks
Results
Significant improvement in sleep quality (PSQI) and depression scores (HAM-D) vs placebo. Urinary serotonin metabolites increased confirming conversion. Good tolerability.
How They Measured It
PSQI, HAM-D, serotonin metabolites
To assess the evidence for L-tryptophan on sleep quality
Study Type
Systematic review
Purpose
To assess the evidence for L-tryptophan on sleep quality
Dose
1000-5000 mg/day
Participants
Systematic review of sleep trials
Duration
Various
Results
Consistent evidence for improved sleep latency and quality. Effect size moderate but clinically meaningful. Serotonin and melatonin precursor role well-established. Better tolerated than older hypnotics.
How They Measured It
Systematic review of sleep studies
Depression & Mood
To evaluate L-tryptophan as antidepressant monotherapy in mild-moderate depression
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate L-tryptophan as antidepressant monotherapy in mild-moderate depression
Dose
6000 mg/day L-tryptophan
Participants
45 patients with mild-moderate depression
Duration
4 weeks
Results
Significant reduction in HAM-D scores vs placebo (p<0.05). 54% response rate vs 18% placebo. BDI also improved. Serotonergic mechanism confirmed.
How They Measured It
HAM-D, BDI, CGI, plasma tryptophan
To compare L-tryptophan with amitriptyline for depression treatment
Study Type
Randomised, double-blind, controlled
Purpose
To compare L-tryptophan with amitriptyline for depression treatment
Dose
3000 mg/day L-tryptophan
Participants
60 depressed outpatients
Duration
6 weeks
Results
L-tryptophan comparable to amitriptyline in antidepressant efficacy. Significantly fewer anticholinergic side effects with tryptophan. Suitable option for patients intolerant of TCAs.
How They Measured It
HAM-D, MADRS, clinical global assessment
Anxiety & Aggression
To evaluate L-tryptophan on anxiety and agitation in healthy adults
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate L-tryptophan on anxiety and agitation in healthy adults
Dose
1000 mg/day L-tryptophan
Participants
25 healthy adults
Duration
2 weeks
Results
Significant reduction in state anxiety (p=0.03) and agitation measures. More pleasant and submissive social behaviour noted by raters. Cortisol levels reduced.
How They Measured It
STAI, mood questionnaires, cortisol, serotonin metabolites
To assess L-tryptophan on quarrelsome and aggressive behaviour
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To assess L-tryptophan on quarrelsome and aggressive behaviour
Dose
1500 mg/day L-tryptophan
Participants
24 healthy adults
Duration
15 days
Results
Significant reduction in quarrelsome behaviour (p<0.05) and increased agreeableness in social interactions. Aggression and dominance reduced. Pleasant behaviour increased.
How They Measured It
Social interaction measures, aggression scales, mood ratings
Appetite & Weight
To evaluate L-tryptophan on appetite, satiety, and caloric intake
Study Type
Randomised, double-blind, placebo-controlled
Purpose
To evaluate L-tryptophan on appetite, satiety, and caloric intake
Dose
2000 mg L-tryptophan before meals
Participants
20 healthy adults
Duration
3-week study
Results
Significant reduction in caloric intake (-20%, p=0.03) and preference for protein-containing foods. Satiety enhanced. Hunger ratings reduced. Serotonin-mediated appetite suppression confirmed.
How They Measured It
Ad libitum food intake, satiety VAS, macronutrient preference
To assess L-tryptophan on carbohydrate intake and binge eating
Study Type
Randomised, placebo-controlled
Purpose
To assess L-tryptophan on carbohydrate intake and binge eating
Dose
3000 mg/day L-tryptophan
Participants
40 overweight women with binge-eating tendencies
Duration
12 weeks
Results
Significant reduction in binge eating episodes (p=0.02) and carbohydrate craving. Body weight reduced by 1.8 kg vs 0.4 kg in placebo. Appetite regulation improved.
How They Measured It
Food diary, carbohydrate intake, binge eating frequency
To review the clinical evidence for L-tryptophan supplementation
Study Type
Systematic review and meta-analysis
Purpose
To review the clinical evidence for L-tryptophan supplementation
Dose
Various
Participants
Systematic review
Duration
Various
Results
Evidence supports sleep, mood, anxiety, and appetite-regulating benefits. Serotonin precursor role central to effects. Safety reestablished post-EMS concern (due to contaminants, not tryptophan itself). Widely useful.
How They Measured It
Systematic review and meta-analysis of sleep, mood, anxiety, and appetite outcomes
Frequently Asked Questions
Common questions about Tryptophan research
There are currently 10 peer-reviewed studies on Tryptophan (L-Tryptophan), involving 790 total participants. Research covers Sleep quality, Depression & mood, Anxiety reduction and 1 more areas. The overall evidence strength is rated as Very Strong.
The evidence is currently rated as "Very Strong Evidence". This rating is based on study design quality (randomisation, blinding, placebo controls), sample sizes, study types (10 human studies), and reported outcomes.
Tryptophan has been researched for: Sleep quality, Depression & mood, Anxiety reduction, Appetite regulation. Each area has its own body of evidence which you can explore in the study breakdowns above.
Yes, 10 out of 10 studies are human trials. Human trials carry more weight in our evidence scoring system.
Similar Supplements
Other supplements researched for similar health goals
