Cardiometabolic · VITD-CVD-01 · v2
Borderline: within 4 points of the Doubtful/Refuted boundary, so a re-grade could land either side.
The question is whether taking vitamin D lowers the risk of serious heart problems like heart attack and stroke. The large trials that were built specifically to test this gave vitamin D or a dummy pill to thousands of people and found no benefit [2][6]. One trial [14] saw a small downward trend in events, but its own authors say the result is still compatible with no effect at all. A trial in kidney-dialysis patients using an activated form of vitamin D found no benefit [17], and a trial in heart-failure patients found no survival benefit and a possible harm signal [9]. The one analysis suggesting benefit [22] was not a randomised trial and only pointed to people who were vitamin D-deficient to begin with. Taken together, the strongest evidence does not show that vitamin D reduces major cardiovascular events for people in general.
The dedicated randomised trials of vitamin D on major cardiovascular events are null: VITAL [2] reported a hazard ratio of 0.97 (95% CI 0.85 to 1.12), ViDA [6] 1.02 (0.87-1.20), and J-DAVID [17] 1.25 (0.94-1.67). D-Health [14] found a non-significant trend (0.91, 0.81 to 1.01) alongside a significant reduction in myocardial infarction (0.81, 0.67 to 0.98), but its authors call the confidence interval consistent with a null finding. EVITA [9] in advanced heart failure found no mortality benefit (1.09, 0.69-1.71) and a greater need for mechanical circulatory support (1.96, 1.04-3.66). The only supportive result, a UK Biobank target-trial emulation [22], showed lower cardiovascular mortality (0.74 to 0.79) but only among vitamin D-deficient or insufficient people. The contested point: The division is whether the D-Health trend [14] and the deficiency-subgroup benefit in [22] amount to a real effect or merely noise and selection. The dedicated primary-population RCTs [2][6][17] point to no event-level benefit, while the only positive signal comes from a non-randomised design restricted to deficient individuals.
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One reviewer's only job is to attack the finding. The challenges below were weighed before the grade was set.
The three dedicated event-endpoint RCTs ([2] HR 0.97, [6] HR 1.02, [17] HR 1.25) are all null, directly contradicting an unqualified claim of CV event reduction.
D-Health [14], the only trend toward benefit, has a CI (0.81-1.01) crossing unity and authors who explicitly call it consistent with a null finding; reading it as support is overreach.
Where it remains uncertain. The sole benefit signal is a non-randomised UK Biobank emulation [22] confined to vitamin D-deficient subgroups (cardiovascular-mortality HR 0.74-0.79), not a randomised general-population finding.
Aleatory
Even the largest trials report intervals spanning benefit and harm (e.g. [17] 0.94-1.67; [9] 0.69-1.71), so chance variation around the point estimates remains substantial.
Epistemic
The corpus lacks a randomised event-endpoint trial restricted to vitamin D-deficient people, the exact group where [22] suggests a benefit.
Inferential
[22] is a target-trial emulation in cohort data; inferring a causal supplementation benefit from it imports confounding and selection the randomised trials were designed to remove.
The load-bearing papers from a corpus of 22, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
Largest primary-prevention RCT shows no reduction in major CV events.
“A major cardiovascular event occurred in 805 participants (396 in the vitamin D group and 409 in the placebo group; hazard ratio, 0.97; 95% CI, 0.85 to 1.12; P=0.69).”
Panel auditInternal validity: high · scope of inference: Generally healthy US men >=50 and women >=55 not selected for vitamin D deficiency.Key limitations: population largely vitamin D replete · fixed single dose
Monthly high-dose RCT null, including in the vitamin D-deficient subgroup.
“The primary outcome of CVD occurred in 303 participants (11.8%) in the vitamin D group and 293 participants (11.5%) in the placebo group, yielding an adjusted hazard ratio of 1.02 (95% CI, 0.87-1.20).”
Panel auditInternal validity: high · scope of inference: Community-resident adults aged 50-84 in New Zealand, monthly bolus dosing.Key limitations: monthly bolus dosing regimen · mostly vitamin D replete at baseline
No mortality benefit in heart failure, with a greater need for mechanical circulatory support.
“Mortality was not different in patients receiving vitamin D (19.6%; n = 39) or placebo (17.9%; n = 36) with a hazard ratio (HR) of 1.09 [95% confidence interval (CI): 0.69-1.71; P = 0.726].”
Panel auditInternal validity: medium · scope of inference: Patients with advanced heart failure and low 25(OH)D levels.Key limitations: mortality not MACE endpoint · greater need for MCS implants with vitamin D · advanced HF population only
3 of 22 papers shown. The full review lists all of them, with the panel’s arbitration →
Claims are graded at each quarterly release, and re-graded between releases only when a pivotal trial lands. Every change is a new version of the claim.
Primary randomized evidence consistently shows no reduction in major cardiovascular events, with only a weak subgroup/observational signal preventing a full refutation.
Release 2026-q4 re-graded every claim from its corpus under protocol v0.19. An earlier release's grade is shown for the record; it came from an earlier protocol and is not a movement.
Assumptions that carry weight but are not themselves established.
The panel records the gap that would most move the claim, and the study that would close it.
RCT confined to vitamin D-deficient participants. The only benefit signal [22] is in deficient subgroups, yet the randomised trials [2][6] enrolled largely replete populations, so the deficient-population effect is untested by randomisation. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A randomised, placebo-controlled event-endpoint trial enrolling only participants with low baseline 25-hydroxyvitamin D, powered for MACE.
Open question: Does vitamin D supplementation reduce major cardiovascular events specifically in people who are vitamin D-deficient at baseline? Why it is still open: Randomised trials [2][6][17] enrolled largely replete populations and were null, while the only benefit signal [22] is a non-randomised emulation limited to deficient subgroups.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 26 Oct 2026 · protocol v0.19