Food and Behaviour Research

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Serum concentrations of vitamin B12 and folate in British male omnivores, vegetarians and vegans: results from a cross-sectional analysis of the EPIC-Oxford cohort study

Gilsing AM, Crowe FL, Lloyd-Wright Z, Sanders TA, Appleby PN, Allen NE, Key TJ. (2010) Eur J Clin Nutr. 64(9): 933-9. Epub 2010 Jul 21. 

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Vegans, and to a lesser extent vegetarians, have low average circulating concentrations of vitamin B12; however, the relation between factors such as age or time on these diets and vitamin B12 concentrations is not clear. The objectives of this study were to investigate differences in serum vitamin B12 and folate concentrations between omnivores, vegetarians and vegans and to ascertain whether vitamin B12 concentrations differed by age and time on the diet.


A cross-sectional analysis involving 689 men (226 omnivores, 231 vegetarians and 232 vegans) from the European Prospective Investigation into Cancer and Nutrition Oxford cohort.


Mean serum vitamin B12 was highest among omnivores (281, 95% CI: 270-292 pmol/l), intermediate among vegetarians (182, 95% CI: 175-189 pmol/l) and lowest among vegans (122, 95% CI: 117-127 pmol/l).

In all, 52% of vegans, 7% of vegetarians and one omnivore were classified as vitamin B12 deficient (defined as serum vitamin B12 <118 pmol/l).

There was no significant association between age or duration of adherence to a vegetarian or a vegan diet and serum vitamin B12.

In contrast, folate concentrations were highest among vegans, intermediate among vegetarians and lowest among omnivores, but only two men (both omnivores) were categorized as folate deficient (defined as serum folate <6.3 nmol/l).


Vegans have lower vitamin B12 concentrations, but higher folate concentrations, than vegetarians and omnivores. Half of the vegans were categorized as vitamin B12 deficient and would be expected to have a higher risk of developing clinical symptoms related to vitamin B12 deficiency.


Vitamin B12 is found only in animal-derived foods, and so people following a strict vegan diet need to obtain B12 from supplements or fortified foods to avoid developing B12 deficiency.

This case-control study assessed Vitamin 12 status in adult males: 226 omnivores, 231 vegetarians and 232 vegans, and found Vitamin B12 deficiency in 52% of the vegans, 7% of vegetarians and only 1 omnivore. 

Enough B12 can be stored within the body that deficiency can take months, or sometimes even years, to manifest.  However, the signs and symptoms of B12 deficiency are many and varied, differ widely between individuals, and can 'mimic' those of numerous different psychiatric, neurological or physical health disorders.  See:

Furthermore, if B12 deficiency goes unrecognised for too long (or occurs in early life when the brain and nervous system are still developing), then the damage can be irreversible. 

These findings suggest that more needs to be done to raise awareness of B12 deficiency risks among those following a vegan diet.