Claim
Vegans need vitamin B12 from supplements or fortified foods; without one, deficiency is common and can cause lasting harm.
Yes. This is the one nutrient a vegan diet cannot supply on its own. A cheap supplement solves it.
Why this rating: Consistent across many surveys and supported by a clear biological mechanism.
Supported by multiple systematic reviews or large, consistent studies using different methods, with few plausible alternative explanations.
Explanation
B12 is made by microbes and reaches humans mainly through animal foods. Plant foods do not reliably contain it.
Deficiency develops slowly and can damage nerves and blood formation. Supplements and fortified foods are effective and inexpensive.
Limitations
- Deficiency rates vary with the marker used and how long people have been vegan.
Methodology
- Systematic review of B12 status studies in vegetarian and vegan populations.
Sources for this claim
Each source links to our record of what it found, its limitations and what we used it for, with a link to the original.
- 1How prevalent is vitamin B12 deficiency among vegetarians?
Roman Pawlak, Scott Parrott, Sudha Raj et al. (2013). Nutrition Reviews.
- 2Serum concentrations of vitamin B12 and folate in British male omnivores, vegetarians and vegans: EPIC-Oxford
A. M. J. Gilsing et al. (2010). .