Vitamin D and vitamin A work together like a team to help your body calm down inflammation and fight off germs better than either one could alone.
See the scientific wording
Vitamin D and vitamin A interact in a synergistic manner to jointly regulate immune and inflammatory signaling pathways.
Unverified — no studies directly back this
We haven't found enough studies to verify this claim yet.
Score breakdown, mechanism chain, raw evidence, ideal studies needed
Related videos
How Fit Body Science checks a claim
- 1
We isolate the claim
Health advice from videos, articles and studies is broken down into single, testable claims.
- 2
We find the research
Each claim is matched against peer-reviewed studies, with every source cited by DOI.
- 3
We grade the evidence
Studies are scored on methodology, statistical rigor, transparency and publication quality.
The fitness and health internet is full of confident claims. We check them against real research.
Every claim on this site is traced back to peer-reviewed studies, scored on methodology and reporting quality, and given a verdict you can audit yourself — sources, DOIs and all.
- Full evidence breakdown and mechanism chains
- Ask our AI anything about a claim or its studies
- Get notified when new research changes a verdict
Vitamin D and vitamin A work together like a team to help your body calm down inflammation and fight off germs better than either one could alone.
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Whether combined vitamin D and A supplementation produces a synergistic (greater-than-additive) effect on immune/inflammatory biomarkers compared to either alone or placebo.
A 4-arm, double-blind, placebo-controlled RCT in healthy adults (n=400) with baseline vitamin D <30 ng/mL and vitamin A <1.05 µmol/L. Participants randomized to: (1) placebo, (2) vitamin D (4000 IU/day), (3) vitamin A (2500 IU/day), (4) vitamin D + A (same doses). Primary outcomes: serum IL-6, TNF-α, and 25(OH)D/retinol levels at 0, 8, 16, and 24 weeks. Secondary: gene expression of VDR, RARα, and NF-κB in PBMCs. Synergy assessed via statistical interaction terms (e.g., ANCOVA with multiplicative interaction). Duration: 24 weeks.
Whether pooled data from existing RCTs show consistent synergistic effects of combined vitamin D and A on inflammatory markers.
Systematic review and meta-analysis of all published RCTs (n≥50 per group) testing combined vitamin D and A supplementation in humans, with pre-specified outcomes: CRP, IL-6, TNF-α, and vitamin D receptor (VDR) or retinoic acid receptor (RAR) expression in immune cells. Only trials with adequate dosing (≥2000 IU D, ≥1500 IU A) and duration (≥12 weeks) included. Synergy quantified using interaction effect sizes (e.g., difference-in-differences between combination vs. single-agent arms). Duration: all included trials ≥12 weeks.
Whether vitamin D and A co-treatment alters transcriptional regulation of immune genes via shared nuclear receptor crosstalk.
Primary human monocytes or dendritic cells treated with: (1) vehicle, (2) 100 nM calcitriol (active D), (3) 1 µM retinoic acid (active A), (4) calcitriol + retinoic acid. Outcomes: ChIP-seq for VDR and RAR binding at promoters of IL-10, TNF, CCL2; RNA-seq for inflammatory gene expression; luciferase reporter assays for NF-κB/AP-1 activity. Synergy defined as >1.5-fold greater effect than additive predicted effect. Duration: 24–72 hours.
Whether combined vitamin D and A deficiency or supplementation alters inflammatory disease severity in vivo via immune pathway modulation.
C57BL/6 mice (n=8/group) fed defined diets: (1) adequate D+A, (2) D-deficient, (3) A-deficient, (4) D+A-deficient, (5) D+A-supplemented. Induced with LPS or DSS-colitis. Outcomes: colonic cytokine levels (IL-17, IFN-γ), Treg/Th17 ratios in mesenteric lymph nodes, VDR/RAR co-localization in intestinal immune cells via immunofluorescence. Duration: 4–6 weeks.
Whether serum levels of vitamin D and A correlate with inflammatory biomarkers in a population, suggesting potential interaction.
Cross-sectional analysis of NHANES or similar cohort (n≥5000) with measured serum 25(OH)D, retinol, CRP, IL-6, and TNF-α. Interaction term (vitamin D × vitamin A) included in multivariate regression adjusting for age, BMI, smoking, and comorbidities. Synergy defined as significant interaction term (p<0.05) with effect size >0.3 SD for inflammatory markers. Duration: single time point.