title: The impact of vegan diet on B-12 status in healthy omnivores: five-year prospective study.
abstract: 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.
  
  
  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.
authors.affiliation: Department of Physiology, Poznań University of Medical Sciences, Święcickiego 6, Poznań, Poland. edytamadry@poczta.onet.pl
authors.forename: Edyta
authors.initials: E
authors.lastname: Mądry
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Lisowska
authors.forename: Philip
authors.initials: P
authors.lastname: Grebowiec
authors.forename: Jarosław
authors.initials: J
authors.lastname: Walkowiak
mesh_terms: D000328:Adult; D014676:Diet, Vegetarian / Q000009:adverse effects*; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D011446:Prospective Studies; D012307:Risk Factors; D013997:Time Factors; D014805:Vitamin B 12; D014806:Vitamin B 12 Deficiency / Q000209:etiology*; D055815:Young Adult
chemical_list: D014805:Vitamin B 12