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5-HTP (5-Hydroxytryptophan)

Also known as: 5-Hydroxytryptophan, oxitriptan, L-5-HTP, 5-hydroxy-L-tryptophan

Effective Dosage

50-300 mg daily (general knowledge; no dose established from provided studies)

What the Science Says

5-HTP is a naturally occurring amino acid derivative and the direct chemical precursor to serotonin, a neurotransmitter that regulates mood, sleep, and appetite. Your body makes 5-HTP from tryptophan found in food, and taking it as a supplement is thought to raise serotonin levels in the brain. It is commonly marketed for mood support, sleep improvement, and appetite control, though the clinical evidence base from the studies provided here is very limited.

What It Doesn't Do

Not a proven antidepressant — don't replace prescribed medications with it. Won't cure anxiety or depression on its own. No solid evidence it causes meaningful weight loss. Not a sleep medication, even if it may have mild effects. The one paper provided focused on tryptophan in anorexia nervosa, not 5-HTP specifically in healthy adults.

Evidence-Based Benefits

5-HTP is a direct precursor to serotonin and melatonin synthesis. A 12-week RCT (PMID: 38309227) found 100 mg/day improved subjective sleep quality and increased serum serotonin in older adults, with benefits most pronounced in poor sleepers. An fMRI RCT (PMID: 34737364) found acute 5-HTP intake influenced social cognition, including stricter moral evaluation and improved recognition of positive emotions in older participants. A review (PMID: 41928689) notes five decades of clinical evidence suggesting 5-HTP can augment SSRI efficacy, though it characterizes 5-HTP as having 'poor drug properties.'

Weak Evidence

Effective at: 100 mg daily based on available RCT data; higher doses used in some contexts

Source: auto-research

Absorption & Bioavailability

Good — 5-HTP crosses the blood-brain barrier more readily than tryptophan and does not compete with other amino acids for transport, making it more efficiently converted to serotonin than dietary tryptophan. However, this is based on general pharmacological knowledge, not the provided studies.

Red Flags to Watch For

  • Do NOT combine with antidepressants (SSRIs, MAOIs, SNRIs) — risk of serotonin syndrome, a potentially life-threatening condition
  • Long-term safety is not well established; some animal studies raised concerns about cardiac valve changes at high doses
  • Can cause nausea, diarrhea, and stomach cramps, especially at higher doses or without food
  • Only one paper was provided and it focused on tryptophan in anorexia nervosa — not direct clinical evidence for 5-HTP supplementation in general populations
  • Widely sold (1,000+ registered products) despite a very thin clinical evidence base — marketing often outpaces the science

Research Sources

  • General knowledge
  • PMID: 28438641 (tryptophan in anorexia nervosa context only)

This information is for educational purposes only and is not medical advice. Always consult a healthcare professional before starting any supplement regimen. Last updated: 2026-04-06