Meta-analysisindependent cross-checkabstract checked I-SUP-124 in-depth review

Vitamin B12 status in vegans

A systematic review and meta-analysis of functional vitamin B12 status among adult vegans.

Overview

Niklewicz A et al.. Nutr Bull 2024 · PMID 39373282 · DOI 10.1111/nbu.12712

Adult vegans had lower B12 and signs of B12 deficiency; those taking B12 supplements had much better values.

Does the study support the specific claim? No · Methodological quality: moderate

Study explained simply

What did the researchers want to find out?: To assess B12 status in vegans.
How was the study done?: Meta-analysis of 17 studies.
How many people, animals or samples were studied?: Adult vegans and comparison groups.
What was actually found?: Vegans more often B12-deficient; supplements correct this.
How large was the observed effect?: Serum B12 SMD -0.72.
What do the results mean in everyday life?: People who eat no animal foods need a B12 supplement.
What are the study's limitations?: Observational; lab markers only.
What does it say about Elawady's specific claim?: Contradicts C-SUP-10's universal rule.
Do the results apply to Germany and Europe?: Applicable.
What can explicitly not be concluded from this study?: Not about people who eat meat regularly.

Authors: Niklewicz A et al.
Journal: Nutr Bull
Year: 2024
Identifier: PMID 39373282 DOI 10.1111/nbu.12712
Verification: verified – PubMed efetch 2026-10-26; Crossref works API 2026-10-26
Retracted: no
Corrections: none
Extent checked: abstract only
Conflicts of interest and funding: No COI statement in PubMed record; funding listed: Biotechnology and Biological Sciences Research Council

Is a vegan diet associated with functional vitamin B12 deficiency, and do supplements help?

Study design: Meta-analysis – Systematic review and meta-analysis of observational studies using functional B12 biomarkers
Population: Adult vegans, vegetarians and omnivores
Country: Multinational
Period: Not stated in abstract
Sample size: 19 studies in review; 17 in meta-analysis
Inclusion and exclusion criteria: Studies reporting B12 biomarkers (serum B12, holoTC, MMA, tHcy) in adult vegans

Exposure / intervention: Vegan diet; B12 supplement use
Comparator: Omnivores; vegetarians; unsupplemented vegans
Endpoints: Serum B12, holotranscobalamin, methylmalonic acid, total homocysteine
Statistical methods: Meta-analysis of standardised mean differences; subgroup by supplement use

Results: Vegans vs omnivores: lower serum B12 (SMD -0.72, -1.26 to -0.18), higher homocysteine (0.57, 0.26-0.89), higher MMA (0.28, -0.01 to 0.57; P=0.06), lower holoTC (-0.42, -0.91 to 0.07; P=0.09). Supplemented vegans had significantly better values in all biomarkers than unsupplemented vegans.
Absolute risks: not reported in abstract
Authors' conclusion: Vegans show increased functional B12 deficiency; appropriate B12 supplementation is needed.

Standardised differences; direction consistent across biomarkers.

Shows a group that needs a supplement (vegans need B12) - contradicts 'no one needs supplements'.

The Tayebat system is not vegan (meat, liver, fish allowed), so this is a general counter-example rather than a system-specific one.

Applicable.

Clear evidence for B12 supplementation need in vegans.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	moderate
Risk of bias	some concerns
Precision of results	moderate
Directness	direct
Reproducibility	replicated
Consistency with the overall evidence	consistent
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Clinical consequences in adults.