The impact of vegan diet on B-12 status in healthy omnivores: five-year prospective study

Acta Sci Pol Technol Aliment. 2012 Apr 2;11(2):209-12.


Background: There are no long-term prospective studies assessing the impact of the vegan diet on vitamin B-12 (B-12) status. Many vegans take B-12 supplements irregularly or refuse to adopt them at all, considering them to be "unnatural" products. The use of B-12 fortified food may be an alternative. Therefore, we aimed to estimate the long-term effect of a vegan diet on serum B-12 concentrations in healthy omnivore adults, comparing the influence of natural products consumption and B-12 fortified food.

Material and methods: A five year prospective study was carried out comprising 20 omnivore healthy adult subjects, who moved to strict vegan diet for 5 years. Ten volunteers followed vegan diet based entirely on natural products, while the remaining ten subjects consumed food fortified in B-12. In all subjects serum vitamin B-12 concentration was determined before and 6, 12, 24 and 60 months after the implementation of the diet.

Results: A significant decrease (p < 0.0002) of serum B-12 concentrations in the whole studied group was noted after 60 months of vegan diet. However, observed changes were in fact limited to the subgroup consuming exclusively natural products (p < 0.0001).

Conclusions: Transition from omnivore to vegan diet is associated with the risk of vitamin B-12 deficiency. B-12 fortified products might constitute a valuable alternative in vegans refusing to take vitamin supplements.

MeSH terms

  • Adult
  • Diet, Vegetarian / adverse effects*
  • Dietary Supplements
  • Female
  • Humans
  • Male
  • Prospective Studies
  • Risk Factors
  • Time Factors
  • Vitamin B 12 Deficiency / etiology*
  • Vitamin B 12*
  • Young Adult


  • Vitamin B 12