Pawlak, Lester and Toyin, 2014

Pawlak, R., Lester, S. E., & Babatunde, T. (2014). The prevalence of cobalamin deficiency among vegetarians assessed by serum vitamin B12: a review of literature. European journal of clinical nutrition, 68(5), 541-548.

Individuals on vegetarian diets risk vitamin B12 deficiency due to insufficient intake. Vitamin B12 is crucial for nucleic acid synthesis, erythrocyte production, and myelin maintenance, so its deficiency can cause various symptoms, some severe or irreversible. This review aimed to evaluate vitamin B12 deficiency in various vegetarian diets, using serum vitamin B12 levels. A systematic literature search utilized PubMed, Medline, CINAHL plus, ERIC, Nursing and Allied Health Collection, and Nursing/Academic Edition. Inclusion criteria were original studies assessing serum vitamin B12, studies in English, non-case studies, and studies reporting actual vitamin B12 deficiency percentages. Forty studies were included.

Infant deficiency prevalence was 45%. In children and adolescents, it ranged from 0 to 33.3%. Pregnant women showed 17 to 39% deficiency, varying by trimester. Adults and the elderly had a 0–86.5% deficiency range.

Vegans reported higher deficiencies than other vegetarians. Generally, the studies showed high deficiency prevalence in vegetarians, with non-supplementing vegans at particularly high risk. Vegetarians, especially vegans, should consider vitamin B12 supplements to ensure sufficient intake. All vegetarians, regardless of diet type, should be screened for vitamin B12 deficiency.

Own notes

Seems legit but most included studies had like 40-60 people. Would be nice to have some sort of meta analysis