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Head-to-head evidence comparison — which supplement is right for you?
Vitamin D3 wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Likely helps
6 of 7 studies with measurable effects showed benefit.
Top outcomes
Verdict
Probably helps
15 of 26 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (1)
Outcomes where both 5-HTP and Vitamin D3 have evidence — compare verdict strength side-by-side.
50-100mg for sleep; 150-300mg for mood
For sleep: 30-45 minutes before bed, For mood: 2-3 divided doses with meals
Capsules
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
2-4 weeks
1-2 weeks
2-4 weeks
First 1-2 weeks
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
Early pharmacological interventions for universal prevention of post-traumatic stress disorder (PTSD)
The Cochrane database of systematic reviews (2022) · Systematic review · n=2023
This review provides uncertain evidence only regarding the use of hydrocortisone, propranolol, dexamethasone, omega-3 fatty acids, gabapentin, paroxetine, PulmoCare formula, Oxepa formula, or 5-hydroxytryptophan as universal PTSD prevention strategies.
Combination pharmacotherapy for the treatment of fibromyalgia in adults
The Cochrane database of systematic reviews (2018) · Systematic review · n=1474
Two studies only reported any primary outcomes of interest (patient-reported pain relief of 30%, or 50%, or greater).
The Impact of 5-Hydroxytryptophan Supplementation on Cognitive Function and Mood in Singapore Older Adults: A Randomized Controlled Trial
Nutrients (2025) · Rct · n=30
Results: A significant time effect was observed in the MoCA score, which was mainly explained by a significant increase in the 5-HTP group (week 0 vs. week 12: 26.6 ± 1.4 a.u. vs. 27.6 ± 1.4 a.u., p < 0.05).
Vitamin D supplementation vs. placebo and incident type 2 diabetes in an ancillary study of the randomized Vitamin D and Omega-3 Trial
Nature communications (2025) · Meta analysis · n=5205
Mean body mass index (BMI) was 27.5 kg/m2 (SD = 5.3), with 51% female and 17% Black race/ethnicity.
Vitamin D Supplementation for Patients with Dysmenorrhoea: A Meta-Analysis with Trial Sequential Analysis of Randomised Controlled Trials
Nutrients (2024) · Meta analysis · n=687
TSA revealed that the current RCTs provide sufficient information.
Vitamin D and respiratory tract infections
BMJ (2017) · Meta analysis · n=11321
12% reduction in respiratory infections overall
Limited evidence from small RCTs (n=30, n=166). Effectiveness constrained by mixed study populations and preliminary findings. Higher doses associated with increased nausea risk.
Meta-analysis showed 12% overall reduction in respiratory infections, with greater benefits in severely deficient individuals. Daily dosing more effective than bolus. Conservative estimate assumes most users not severely deficient.
AI-estimated from published studies. Interpret as directional guidance.
Vitamin D3 has a higher evidence score (9/10 vs 8.5/10) and wins in 3 of 3 categories.
Both 5-HTP and Vitamin D3 score equally (75) for support mood.
No known interactions between 5-HTP and Vitamin D3 have been documented in our database. However, always consult a healthcare provider before combining supplements.