NSTK · 01.2026Independent supplement reference
NutriStack
Edition 1.0Updated August 1, 2026

Supplement × Supplement·Evidence index

5-HTP and Melatonin: what the published research says

PubMed indexes 8 records that name 5-HTP and Melatonin together, either in the title or in an interaction, co-administration, or pharmacokinetic context. Each one is listed below with its study design and, where the abstract states one, the authors’ own conclusion, quoted and linked. This page reports that literature. It does not tell you whether to combine them.

Read this first

An evidence index, not guidance.

Every statement below is attributed to a named, dated, linked source.

This page lists published research relevant to 5-HTP and Melatonin. It deliberately does not state whether the combination is safe, whether it interacts, in which direction, at what dose, or how far apart to take them.

The research

8 studies naming 5-HTP and Melatonin.

Strongest relevance first: papers naming both substances in the title, then human trials and systematic reviews.

Detection of melatonin and 5-HTP in dietary supplements based on multiple spectra.

Frontiers in nutrition · 2025 · PMID 39935577

“Finally, it is demonstrated that THz technology can effectively detect melatonin and 5-HTP in commercial dietary supplements. This study establishes a rapid, efficient, and non-destructive approach for the regulation and quantitative analysis of dietary supplements.”

Yang et al. · From the abstract

Names both 5-HTP and Melatonin in its title.

Effects of Duodenal 5-Hydroxytryptophan Perfusion on Melatonin Synthesis in GI Tract of Sheep.

Molecules (Basel, Switzerland) · 2021 · PMID 34500708

Animal study

“The current study provides further evidence to support that GI tract is the major site for melatonin synthesis and the GI melatonin also contributes to the circulatory melatonin level since plasma melatonin concentrations in 5-HTP treated groups were significantly higher than those in the control group.”

Pan et al. · From the abstract

Names both 5-HTP and Melatonin in its title.

Rumen-Protected 5-Hydroxytryptophan Improves Sheep Melatonin Synthesis in the Pineal Gland and Intestinal Tract.

Medical science monitor : international medical journal of experimental and clinical research · 2019 · PMID 31091223

Animal study

“In addition, the AADC (P<0.01) and AA-NAT (P<0.05) gene expression levels in the duodenum and jejunum were increased by the supplementation of RP 5-HTP. CONCLUSIONS Rumen-protected 5-hydroxytryptophan promoted melatonin synthesis in the pineal gland and intestinal tract during the natural light period.”

Zhao et al. · From the abstract

Names both 5-HTP and Melatonin in its title.

5-hydroxytryptophan is a more potent in vitro hydroxyl radical scavenger than melatonin or vitamin C.

Journal of pineal research · 2005 · PMID 15617538

“For vitamin C an IC50 of 12.7 microm was measured, whereas melatonin in pure demineralized water was much less efficient (IC50=724 microm). A comparison between melatonin in aqueous solution and melatonin in ethanol solution revealed that melatonin was significantly more effective in pure demineralized water.”

Keithahn et al. · From the abstract

Names both 5-HTP and Melatonin in its title.

Elevation of melatonin in chicken retina by 5-hydroxytryptophan: differential light/dark responses.

Neuroreport · 1998 · PMID 9926844

Animal study

“The results suggest that TPH, but not AA-NAT or other enzymes in the melatonin biosynthetic pathway, is saturated with substrate in situ. The rate of melatonin production appears to be a function of the concentration of serotonin, which is regulated by TPH, and by the level of activity of AA-NAT.”

Thomas et al. · From the abstract

Names both 5-HTP and Melatonin in its title.

Limitations

What this evidence cannot tell you.

Search-based evidence indexes have real limits, and it is worth being explicit about them:

NutriStack

Track what you actually take.

NutriStack is a free iPhone app for organising a supplement routine: what you take, when, and what the published record says about it. Its exploratory interaction checker covers 5-HTP, Melatonin, and several hundred other substances.

The checker is a research and organisation tool, not a clinical decision aid, and its per-pair assessments are excluded from search until they pass claim-level review.

NutriStack is an informational and organizational tool, not a medical service, and not a substitute for professional advice. Always consult a qualified healthcare professional before starting, stopping, or changing any supplement or medication.