Margalit I, et al. - Gender differences in vitamin B12 deficiency were assessed among a healthy population (aged 18–65), excluding individuals with background illnesses and those who had used medications or nutritional supplements. Vitamin B12 deficiency was defined by 2 cutoff values (206 and 140 pmol/L). The susceptibility to developing vitamin B12 deficiency was noted in men among the healthy population. Neither diet habits nor estrogen effects explained this finding. Genetic variations are therefore hypothesized to play a role.