priors.science/reviews/vitamin-b12

Vitamin B12

The current evidence on 9 claims, ordered from most established to most contested. Each score is the panel’s evidence certainty: how firmly the literature supports the claim as stated.

9claims tracked
152primary papers reviewed
4 Oct 2026latest evidence review
3 Established · 1 Likely · 2 Uncertain · 2 Doubtful · 1 Refuted  |  four-reviewer panel · PICO Framework
ClaimStandingEvidence certaintyCorpus
Metformin lowers vitamin B12Deficiency And StatusEstablished90%22
Vitamin B12 lowers homocysteineHomocysteine CardiovascularEstablished87%20
Vegans risk vitamin B12 deficiencyDeficiency And StatusEstablished86%20
B vitamins reduce strokeHomocysteine CardiovascularLong-standingLikely71%20
Oral vitamin B12 matches injectionDeficiency And StatusUncertain65%20
Vitamin B12 corrects deficiency neuropathyNeurocognitionUncertain55%20
Maternal vitamin B12 aids neurodevelopmentNeurocognitionDoubtful45%20
Vitamin B12 halts cognitive declineNeurocognitionDoubtful30%20
B vitamins cut cardiac eventsHomocysteine CardiovascularLong-standingRefuted12%20
Track Vitamin B12.
These claims are re-checked against new research as it is published. Track this topic for the full review, including each claim’s challenge and the papers behind it.
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Standing: what the evidence certainty means
Established≥ 85%Strong, consistent evidence. Unlikely to change.
Likely70–84%Well supported, with some gaps or indirect evidence.
Uncertain50–69%Mixed or limited evidence. Genuinely open.
Doubtful30–49%Little support; the weight of evidence leans against it.
Refuted< 30%The evidence contradicts it. Confidently false as stated.
A standing changes only when the score moves past a boundary by more than 4 points, the re-scoring noise floor; a score within 4 points of a boundary keeps its previous standing.
Where the evidence sits in time
Long-standingMost of this evidence is older than the rest of this field.