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
10 Aug 2026latest evidence review
Weeklyre-scored against new papers
3 Established · 1 Likely · 2 Uncertain · 2 Doubtful · 1 Refuted  |  four-reviewer panel · PICO Framework
ClaimStandingEvidence certaintyCorpus
Vitamin B12 lowers homocysteineHomocysteine CardiovascularEstablished90%20
Vegans risk vitamin B12 deficiencyDeficiency And StatusEstablished88%20
Metformin lowers vitamin B12Deficiency And StatusEstablished86%22
Vitamin B12 corrects deficiency neuropathyNeurocognitionLikely82%20
Oral vitamin B12 matches injectionDeficiency And StatusUncertain68%20
B vitamins reduce strokeHomocysteine CardiovascularLong-standingUncertain56%20
Maternal vitamin B12 aids neurodevelopmentNeurocognitionDoubtful46%20
Vitamin B12 halts cognitive declineNeurocognitionDoubtful30%20
B vitamins cut cardiac eventsHomocysteine CardiovascularLong-standingRefuted18%20
Track Vitamin B12.
These claims are re-scored against new papers every week. 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.
Where the evidence sits in time
Long-standingMost of this evidence is older than the rest of this field.