A new review from the US confirms that vegetarians develop vitamin B12 depletion or deficiency regardless of demographic characteristics, place of residency, age, or type of vegetarian diet.
To assess the rate of vitamin B12 depletion and deficiency among vegetarians and vegans, 18 studies which measured vitaminB12 status (serum holo-transcobalamin II and/or methylmalonic acid concentrations) of different population groups adhering to different types of vegetarian diets were reviewed (1). The deficiency rates reported for specific populations were as follows: 62% among pregnant women, between 25% and almost 86% among children, 21–41% among adolescents, and 11–90% among the elderly. Higher rates of deficiency were reported among vegans compared with vegetarians and among individuals who had adhered to a vegetarian diet since birth compared with those who had adopted such a diet later in life.
The researchers commented that health professionals should alert vegetarians about the risk of developing subnormal vitamin B12 status. Vegetarians should also take preventive measures to ensure adequate intake of the vitamin, including the regular intake of vitamin B12 supplements to prevent deficiency. Considering the low absorption rate of vitamin B12 from supplements, an adequate dose should be ingested for the best results.
Vitamin B12 is only synthesized by microorganisms and is, thus, not found in foods of plant origin, except through contamination with soil or by exposure to foods containing vitamin B12, such as milk solids during processing or in foods fortified with this vitamin. Since vegetarians have limited natural sources of B12 (milk, dairy, and eggs), the presence of B12 in plant-based diets depends on the inclusion/exclusion of foods of animal origin, consumption of foods fortified with B12, or the use of vitamin B12 supplements. Deficiency symptoms of the vitamin may be mild to severe. Mild symptoms, such as lethargy or forgetfulness may not even be detected or may be associated with other issues, such as aging or tiredness due to other reasons. Hematological symptoms, such as elevated mean corpuscular volume of erythrocytes, may not be shown in biochemical assessments, as such symptoms may be masked by either iron deficiency or high intake of folate; vegetarians are more likely to have both.