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Head-to-head evidence comparison — which supplement is right for you?
Vitamin D3 wins 1 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Mostly mechanism / observational
0 of 2 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 SAMe and Vitamin D3 have evidence — compare verdict strength side-by-side.
400-1600mg for mood; 600-1200mg for joints
On empty stomach, Morning and/or midday
Enteric-coated tablets (SAMe tosylate or butanedisulfonate)
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
2-6 weeks
4-8 weeks
4-8 weeks
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
S-Adenosylmethionine for osteoarthritis of the knee or hip
The Cochrane database of systematic reviews (2009) · Meta analysis · n=656
For pain, the analysis indicated a small SMD of -0.17 (95% CI -0.34 to 0.01), corresponding to a difference in pain scores between SAMe and placebo of 0.4 cm on a 10 cm VAS, with no between trial heterogeneity (I(2) = 0).
Efficacy of Pharmacological Interventions in Milder Depression: A Systematic Review and Meta-Analysis
Neuropsychopharmacology reports (2025) · Meta analysis · n=1049
A meta-analysis found no significant difference in response rates between the two treatments (risk ratio [RR] = 0.96, 95% CI: 0.78-1.18) or dropout rates (RR = 1.08, 95% CI: 0.62-1.88).
S-Adenosylmethionine (SAMe) for Liver Health: A Systematic Review
Nutrients (2024) · Systematic review · n=15
The most common doses were SAMe 1000 mg or 1200 mg per day with or without another treatment or natural supplement.
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
Meta-analysis of 656 patients showed small effect size (SMD -0.17) corresponding to only 0.4cm improvement on 10cm pain scale. Effect is modest and barely reaches statistical significance threshold.
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 9/10) and wins in 1 of 3 categories.
For support mood, SAMe has a higher relevance score (90 vs 75).
No known interactions between SAMe and Vitamin D3 have been documented in our database. However, always consult a healthcare provider before combining supplements.