Reviews/Vitamin B12/B vitamins cut cardiac events
Homocysteine Cardiovascular · VITB12-CV-02 · v2
Several large, well-run trials gave people B vitamins to lower a blood chemical called homocysteine and then counted heart attacks, strokes and cardiovascular deaths. The vitamins reliably lowered homocysteine by roughly a fifth to a quarter, yet the number of major heart events was essentially the same as with placebo [1][2][3][5][6]. Trials in kidney-disease patients found the same lack of benefit [4][8][9][11]. The only trial reporting fewer events was small, run at a single centre, and did not fully randomise its groups [14]. Set against tens of thousands of patients showing no effect, and a scattering of signals pointing the wrong way [17], the panel concluded the evidence contradicts the claim.
Five large double-blind placebo-controlled RCTs totalling roughly 29,000 patients lowered homocysteine 19-28% but showed no reduction in the primary cardiovascular composite: NORVIT RR 1.08 (0.93-1.25) [1], HOPE-2 RR 0.95 (0.84-1.07) [2], WAFACS RR 1.03 (0.90-1.19) [3], SU.FOL.OM3 HR 0.90 (0.66-1.23) [5] and SEARCH RR 1.04 (0.97-1.12) [6], every interval crossing 1. Renal-population trials concur, including Jamison CKD/ESRD (mortality HR 1.04, 0.91-1.18) [4], FAVORIT (HR 0.99, 0.84-1.17) [8], the German ESRD trial [9] and renal HOPE-2 (RR 1.19, 0.88-1.61) [11]. VITATOPS returned a borderline composite (RR 0.91, 0.82-1.00, p=0.05) driven by stroke rather than the full composite [7]. Surrogate-endpoint studies show favourable movement on flow-mediated dilation [13], arterial stiffness [18] and Framingham score [20], but none measured events. The contested point: The evidence divides on whether any subgroup benefits: HOPE-2 showed fewer strokes (RR 0.75, 0.59-0.97) inside a null composite [2], VITATOPS was borderline for its composite [7], and a post-hoc VITATOPS analysis found a benefit only in patients not taking antiplatelet drugs (HR 0.76, 0.60-0.96) [12]. The panel treated these as isolated, fragile or hypothesis-generating rather than as evidence the primary composite is reduced.
All 20 papers behind this claim with their DOIs and what each does to it, the panel’s arbitration, the evidence gap map and the open research questions. Free, and sent to your inbox.
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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 claim asserts a reduction, but every large placebo-controlled RCT [1][2][3][5][6] returns a null composite with CIs spanning 1, despite confirmed 19-28% homocysteine lowering — the intervention is biologically active yet clinically inert on events.
Apparent positive signals are isolated components or subgroups, not the major CV composite: HOPE-2's stroke reduction sits inside a null composite, and VITATOPS' composite is borderline (RR 0.91, upper CI 1.00, p=0.05).
Where it remains uncertain. The only trial reporting fewer events is single-centre, N=114, with a non-randomised folate arm [14], and a post-hoc subgroup [12] plus HOPE-2's stroke component [2] hint at benefit that the primary composites do not confirm.
Aleatory
The lone positive result rests on 114 patients and a chi-square of borderline significance (p=0.05) [14], where the play of chance dominates.
Epistemic
Whether a real benefit exists in patients not on antiplatelet therapy is unresolved; the only signal is a post-hoc VITATOPS subgroup, HR 0.76 (0.60-0.96) [12].
Inferential
Favourable movement on flow-mediated dilation [13], arterial stiffness [18] and Framingham score [20] does not translate to fewer events, so inference from these surrogates would mislead.
The load-bearing papers from a corpus of 20, each classified by what it does to the claim. Every DOI is taken from the corpus the claim was graded on.
HOPE-2 (N=5522); composite RR 0.95 (0.84-1.07), directly negating the claim.
“Supplements combining folic acid and vitamins B6 and B12 did not reduce the risk of major cardiovascular events in patients with vascular disease.”
Panel auditInternal validity: high · scope of inference: Patients 55+ with established vascular disease or diabetes.Key limitations: excess unstable-angina hospitalisations in active arm · modest homocysteine reduction of 2.4 micromol/L
WAFACS (N=5442); composite RR 1.03 (0.90-1.19) despite 18.5% homocysteine drop.
“did not reduce a combined end point of total cardiovascular events among high-risk women, despite significant homocysteine lowering.”
Panel auditInternal validity: high · scope of inference: US women health professionals aged 42+ with CVD history or 3+ coronary risk factors.Key limitations: nested within an antioxidant trial · women-only population
CKD/ESRD RCT (N=2056); no vascular benefit.
“Treatment with high doses of folic acid and B vitamins did not improve survival or reduce the incidence of vascular disease in patients with advanced chronic kidney disease or end-stage renal disease.”
Panel auditInternal validity: high · scope of inference: Advanced CKD or ESRD patients with high baseline homocysteine.Key limitations: renal-failure population may not generalise · primary endpoint was mortality not a CV composite
NORVIT (N=3749); no effect (RR 1.08) plus harm trend (RR 1.22, P=0.05) in triple arm.
“Treatment with B vitamins did not lower the risk of recurrent cardiovascular disease after acute myocardial infarction.”
Panel auditInternal validity: high · scope of inference: Secondary prevention in men and women within seven days of an acute myocardial infarction.Key limitations: single post-MI population · confidence interval spans no effect for main comparison
4 of 20 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.
A large, concordant body of high-quality RCTs demonstrates that B-vitamin homocysteine lowering does not reduce major cardiovascular events, refuting the claim.
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.
Prospective antiplatelet-naive trial. The sole subgroup signal of benefit sits in a post-hoc VITATOPS analysis (HR 0.76, 0.60-0.96) [12] and cannot support the claim on its own. The panel rates this the highest-importance open gap for the claim, and names the study design that would close it: A prospectively randomised trial of B vitamins versus placebo restricted to patients not on antiplatelet therapy, powered on the major CV composite.
Open question: Do B vitamins reduce major cardiovascular events specifically in patients not receiving antiplatelet therapy? Why it is still open: The only supportive signal is an explicitly post-hoc VITATOPS subgroup (HR 0.76, 0.60-0.96) [12] that adjusted for baseline imbalances after the fact.
Priors is a sceptical first reader, not peer review, and not medical advice.
Release 2026-q4 · graded 18 Sep 2026 · protocol v0.19