Serum Vitamin B12 Levels in Two Subpopulations of Healthy Workers in Israel: Differences by Land of Birth

Abstract

Background In humans, vitamin B 12 participates in two particularly important metabolic reactions. The methyl-cobalamin form of vitamin B 12 serves as the cofactor of cytoplasmic methionine synthase, which catalyzes ultimately yields methionine [1]. It is thus not surprising that vitamin B 12 deficiency is associated with elevated plasma homocysteine [2]. Coenzyme B 12 (adenosyl-cobalamin) also serves as the cofactor of mitochondrial methylmalonyl-CoA, which is transformed to succinyl-CoA [3]. Micronucleus formation, an indicator of genetic instability, has been shown to be reduced when plasma vitamin B12 is > 300 pmol/L [4]. Vitamin B 12 deficiency is typically defined as serum cobalamin levels < 148 pmol/L however, levels consistent with subclinical deficiency have not been defined [5]. Using this cutoff , however, variability in vitamin B 12 deficiency rates has been reported. Predictably, clinical and subclinical deficiency rates are lower in western populations and higher in developing populations. Deficiency is exacerbated by vegetarianism. In India, for example, which is both developing and includes a large vegetarian population, 70% of adults and 80% of preschool children are estimated to be deficient [6]. Use of this cutoff remains controversial, and would likely misclassify up to 50% of cases [3]. For this reason, a cutoff of 258 pmol/L has been proposed, particularly for use in older populations [7]. Variability in population levels and lack of clarity in defining deficiency are the basis for the present study, in which serum vitamin B 12 levels were studied in a convenience sample of health care workers undergoing routine blood chemistry analysis in Israel. Using the actual serum cobalamin level and a variety of cutoffs , vitamin B 12 levels were compared between health care workers born in Israel and those who immigrated to the country.