Loading…
We use essential cookies (authentication, your saved goals/stack) by default. With your permission we’ll also enable privacy-respecting analytics (Vercel Web Analytics, anonymous load-time metrics) and error-replay diagnostics (Sentry — DOM snapshots only when an error fires) so we can fix bugs faster. Learn more about cookies
Head-to-head evidence comparison — which supplement is right for you?
Vitamin A vs Vitamin D3: Vitamin D3 has the stronger overall evidence (7.5 vs 7/10); they're alternatives for support immune system — the best pick depends on your goals. Take the 60-second quiz for a pick tailored to your goals.
Vitamin D3 wins 3 of 3 categories. Both are solid choices — the best pick depends on your specific goals.
Verdict
Mixed evidence
8 of 17 studies with measurable effects showed benefit.
Top outcomes
Verdict
Probably helps
13 of 23 studies with measurable effects showed benefit.
Top outcomes
Shared outcomes (2)
Outcomes where both Vitamin A and Vitamin D3 have evidence — compare verdict strength side-by-side.
2500-5000 IU daily (retinol); up to 25000 IU (beta-carotene)
With fat-containing meal, Any time of day
Mixed carotenoids or low-dose retinyl palmitate
2000-4000 IU daily
Morning with breakfast
D3 (cholecalciferol) softgel or liquid
and 2 more not shown
and 1 more not shown
Very high vitamin A may interfere with vitamin D signaling
Avoid very high doses of vitamin A (>10,000 IU) with vitamin D therapy.
2-4 weeks
2-4 weeks
4-8 weeks
With chronic excess
4-8 weeks
4-8 weeks
2-4 weeks
4-8 weeks
Effects of primary or secondary prevention with vitamin A supplementation on clinically important outcomes: a systematic review of randomised clinical trials with meta-analysis and trial sequential analysis
BMJ open (2024) · Meta analysis · n=672
Vitamin A did not reduce mortality in individually randomised trials (RR 0.99, 95% CI 0.93 to 1.05; I²=32%; p=0.19; 105 trials; moderate certainty), and this effect was not affected by the risk of bias.
Vitamin and Mineral Supplementation During Pregnancy on Maternal, Birth, Child Health and Development Outcomes in Low- and Middle-Income Countries: A Systematic Review and Meta-Analysis
Nutrients (2020) · Meta analysis · n=451723
IFA supplementation showed notable improvement in maternal anemia and the reduction in low birthweight, whereas LNS supplementation had no apparent effect on outcomes; further research that compares LNS and MMN supplementation could help understand differences with these commodities.
Vitamin A supplements for reducing mother-to-child HIV transmission
The Cochrane database of systematic reviews (2017) · Meta analysis · n=6601
Antepartum or postpartum vitamin A supplementation, or both, probably has little or no effect on mother-to-child transmission of HIV in women living with HIV infection and not on antiretroviral drugs.
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 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 (7.5/10 vs 7/10) and wins in 3 of 3 categories.
For support immune system, Vitamin D3 has a higher relevance score (92 vs 75).
Very high vitamin A may interfere with vitamin D signaling Avoid very high doses of vitamin A (>10,000 IU) with vitamin D therapy. Consult a healthcare provider for personalized advice.
Commonly recommended vs ask-your-clinician vs avoid — a general, safety-first overview.
The honest tier list — proven staples vs situational vs mostly marketing. The hub the other guides feed into.
On Ozempic/Wegovy/Mounjaro? What actually helps — muscle preservation, GI relief, nutrient gaps (no upsell).
Tired? Why most "energy" pills only work if they fix a deficit — and how to find yours first.
The right pick depends on your goals. Answer a few quick questions for a personalised recommendation — or dig into the full evidence on each.