Limited evidenceStress & mood

5-HTP

Despite decades of popularity as a natural antidepressant, 5-HTP's clinical evidence is thin and dated: systematic reviews found almost no trials of acceptable quality, and the drug-interaction risk is real.

What the science says

Antidepressant evidence does not meet modern standards Limited evidence
A Cochrane review and its companion meta-analysis identified 108 trials of 5-HTP and tryptophan for depression, but only 2 studies totalling 64 participants met basic quality criteria. Those two favoured the amino acids over placebo, but the reviewers explicitly concluded the evidence base is too small and too flawed to support clinical use.
Fibromyalgia and migraine claims rest on small, old, mostly open-label studies Limited evidence
The frequently cited fibromyalgia and migraine prophylaxis trials date from the 1980s-90s, involved fewer than 100 participants each, and were often unblinded or lacked placebo controls. No adequately powered modern replication exists for either indication.
Appetite and weight-loss effects are unreplicated Limited evidence
A handful of small trials in the late 1980s and 1990s reported reduced calorie intake and modest weight loss with 600-900 mg/day of 5-HTP, but nausea was frequent enough to compromise blinding. These findings have not been confirmed in contemporary controlled trials.

Dosage & safety

Studied doseTrials used 150-800 mg/day in divided doses, commonly 100-300 mg/day for mood and up to 900 mg/day in appetite studies. Products are often paired with carbidopa in research settings to prevent peripheral conversion; consumer products are not.

SafetyNausea is common and dose-limiting; also reported are diarrhea, drowsiness and vivid dreams. The major hazard is serotonin syndrome when combined with SSRIs, SNRIs, MAOIs, tricyclics, triptans, tramadol, St John's wort or lithium — this combination should be avoided outright. Some commercial 5-HTP has contained 'peak X', a contaminant chemically related to the compounds implicated in the 1989 eosinophilia-myalgia syndrome outbreak, though no confirmed EMS cases have been attributed to 5-HTP. Long-term use has been theorized to deplete dopamine, and there are case reports of cardiac valve concerns via peripheral serotonin, neither firmly established. 5-HTP is prescription-only or otherwise restricted in several countries, including Australia and Canada.

Scientific references

Tryptophan and 5-hydroxytryptophan for depression
Shaw K, et al. — Cochrane Database Syst Rev, 2002
Are tryptophan and 5-hydroxytryptophan effective treatments for depression? A meta-analysis
Shaw K, et al. — Aust N Z J Psychiatry, 2002

Where to buy

NOW Foods, 5-HTP, 100 mg, 120 Veg Capsules

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