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

Background: Clinical and subclinical vitamin B12 deficiency rates are lower in western populations compared to developing populations and cut-off points for defining deficiency are inconsistent.  Objectives: The present study was designed to examine variability in vitamin B12 blood levels in a heterogeneous population. Methods: The present report is a cross-sectional analysis of serum vitamin B12 levels recorded for 1969 apparently healthy hospital workers employed at Tel Aviv Medical Centre, Tel Aviv, Israel, who underwent blood vitamin B12 tests evaluation as part of the routine occupational health evaluation. Data were extracted from the electronic employee medical record. Results: Almost 73% of the study population was born in Israel, and 73.6% of the population was female. Serum vitamin B12 levels were significantly lower in Israeli born women than in women born outside of Israel: 294±119.9 vs. 320±121.7pmol/L. Land of birth and sex were significant, independent predictors of serum vitamin B12 levels even after controlling for age and year in which the serum vitamin B12 was measured. In a logistic regression model of serum vitamin B12 < 350 pmol/L, land of birth emerged as the only significant, independent predictor, such that being born in Israel increased odds of serum vitamin B12 < 350 pmol/L by a relative 44% (95% CI 17-78%, p=0.001). Discussion: Wide serum vitamin B12 level variability in heterogeneous populations suggests that cut-offs for deficiency may need to be subgroup-specific in order to be clinically meaningful. It is not clear whether presently used clinical cut-offs are associated with increased morbidity in a given population.