Tryptophan
L-Tryptophan
An essential amino acid that serves as the precursor to serotonin and melatonin for mood and sleep support.
L-Tryptophan is an essential amino acid that the body cannot produce, requiring dietary intake. It's the sole precursor to serotonin (the 'feel-good' neurotransmitter) and subsequently melatonin (the sleep hormone). Unlike 5-HTP, tryptophan is one step earlier in the synthesis pathway, offering a more gradual approach to supporting mood and sleep.
Mechanisms of Action
Serotonin Precursor
Converts to serotonin, supporting mood and well-being
Melatonin Synthesis
Serotonin is further converted to melatonin for sleep
Niacin Pathway
Can also be converted to niacin (vitamin B3)
Recommended Dose
500-1000mg before bed
Loading: Not applicable; start with lower dose and adjust
Optimal Timing
- 30-60 minutes before bed
- On empty stomach or with carbohydrates
Can be taken without food
Best Form
L-Tryptophan capsules
Alternatives: Powder, Tablets
Use pharmaceutical-grade L-Tryptophan from reputable sources to ensure purity.
Duration
Minimum: 2 weeks
Optimal: 8 weeks
Cycling: Not required
Note: Taking with carbohydrates may enhance brain uptake by reducing competition from other amino acids. Avoid taking with high-protein foods.
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Faster Sleep Onset
Fall asleep more quickly
Improved Mood
Better overall sense of well-being
Reduced Anxiety
Calming effect through serotonin pathway
Daytime Drowsiness
May cause sleepiness if taken during the day
Consult healthcare provider; limited data
Start with lower doses; may be more sensitive to sedation
Who Should NOT Take This
- Taking SSRIs, SNRIs, or MAOIs (serotonin syndrome risk)
- Eosinophilia-myalgia syndrome history
Drug Interactions
Risk of serotonin syndrome - do not combine
May enhance sedative effects
Increased serotonin syndrome risk
High risk of serotonin syndrome
Possible Side Effects
Tip: Take only before bed; reduce dose if excessive
Tip: Take with a small amount of food
Warnings
- Do NOT combine with serotonergic medications
- Use only pharmaceutical-grade products from reputable manufacturers
Top studies from 40+ peer-reviewed papers
Almulla AF et al. • Cells (2022)
“Patients with affective disorders with melancholic and psychotic features and suicidal behaviors showed normal IDO enzyme activity but a lowered availability of plasma/serum TRP to the brain, which is probably due to other processes such as low albumin levels.”
Key Findings:
- Severe patients showed significant lower (p < 0.0001) TRP (standardized mean difference, SMD = -0.517, 95% confidence interval, CI: -0.735; -0.299) and TRP/CAAs (SMD = -0.617, CI: -0.957; -0.277) levels with moderate effect sizes, while no significant difference in CAAs were found.
- Kynurenine (KYN) levels were unaltered in severe MDD/BD phenotypes, while the KYN/TRP ratio showed a significant increase only in patients with psychotic features (SMD = 0.224, CI: 0.012; 0.436).
- Quinolinic acid (QA) was significantly increased (SMD = 0.358, CI: 0.015; 0.701) and kynurenic acid (KA) significantly decreased (SMD = -0.260, CI: -0.487; -0.034) in severe MDD/BD.
Hughes JR et al. • The Cochrane database of systematic reviews (2014)
“The antidepressants bupropion and nortriptyline aid long-term smoking cessation.”
Key Findings:
- There was high quality evidence that, when used as the sole pharmacotherapy, bupropion significantly increased long-term cessation (44 trials, N = 13,728, risk ratio [RR] 1.62, 95% confidence interval [CI] 1.49 to 1.76).
- There was moderate quality evidence, limited by a relatively small number of trials and participants, that nortriptyline also significantly increased long-term cessation when used as the sole pharmacotherapy (six trials, N = 975, RR 2.03, 95% CI 1.48 to 2.78).
- There is insufficient evidence that adding bupropion (12 trials, N = 3487, RR 1.9, 95% CI 0.94 to 1.51) or nortriptyline (4 trials, N = 1644, RR 1.21, 95% CI 0.94 to 1.55) to nicotine replacement therapy (NRT) provides an additional long-term benefit.
- Pooled results from four trials comparing bupropion to varenicline showed significantly lower quitting with bupropion than with varenicline (N = 1810, RR 0.68, 95% CI 0.56 to 0.83).
Saarto T et al. • The Cochrane database of systematic reviews (2005)
“Antidepressants are effective for a variety of neuropathic pains.”
Key Findings:
- Amitriptyline has an NNT of 2 (95%CI 1.7 to 2.5) RR 4.1(95%CI 2.9-5.9) for the achievement of at least moderate pain relief.
- For diabetic neuropathy the NNT for effectiveness was 1.3 (95%CI 1.2 to 1.5) RR 12.4(95%CI 5.2-29.2) (five studies); for postherpetic neuralgia 2.2 (95%CI 1.7 to 3.1), RR 4.8(95%CI 2.5-9.5)(three studies).
- The number needed to harm(NNH) for major adverse effects defined as an event leading to withdrawal from a study was 16 (95%CI: 10-45).
- The NNH for minor adverse effects was 4.6 (95%CI 3.3-6.7)
Ma T et al. • Cell reports. Medicine (2025)
“All rights reserved.”
Key Findings:
- A randomized, double-blind, placebo-controlled crossover trial involving 110 adults with chronic constipation (Rome IV criteria) demonstrates that a 3-week Probio-Eco intervention significantly improves constipation symptoms, stool straining, and worry scores.
- These findings highlight the comprehensive efficacy of Probio-Eco and provide robust evidence for its clinical application in constipation management.
- This study was registered at Chinese Clinical Trial Registry (ChiCTR2100054376).Copyright © 2025 The Authors.
- Published by Elsevier Inc.
Cheng YC et al. • Psychological medicine (2025)
“This extensive systematic review and NMA of nutraceuticals for treating depressive disorders indicated a number of nutraceuticals that could offer benefits, either as adjuncts or monotherapies.”
Key Findings:
- Adjunctive nutraceuticals consistently showed better efficacy than antidepressants (ADT) alone in outcomes including SMD, remission, and response.
- This extensive systematic review and NMA of nutraceuticals for treating depressive disorders indicated a number of nutraceuticals that could offer benefits, either as adjuncts or monotherapies.
- Further research warranted to confirm findings
Study Type Distribution
Goals This Supplement Supports
Related Goals
This information is for educational purposes only and is not intended as medical advice. Always consult a qualified healthcare provider before starting any supplement.