Association between smoking status and vitamin B12 levels in Jordanian adults: A cross-sectional study of active, passive, and non-smokers.

This cross-sectional study investigated the association between smoking status and serum vitamin B12 concentrations in a Jordanian adult population, using plasma cotinine as a validated biomarker of tobacco exposure. Tobacco use remains a major public health concern in Jordan, where smoking prevalence is among the highest globally. Although previous studies have explored the link between smoking and vitamin B12 status, findings have been inconsistent, and the effects of passive smoke exposure are not well understood. A total of 251 Jordanian adults from Amman and Madaba governorates were categorized as active smokers (n=125), passive smokers (n=63), or non-smokers (n=63). Non-parametric tests (Kruskal-Wallis and Mann-Whitney U) were used to compare group differences, and multiple linear regression was performed on log-transformed vitamin B12 concentrations to identify independent predictors. Vitamin B12 levels differed significantly across groups (p=0.021), with passive smokers showing the highest median concentrations (373.0 pg/mL) compared with active smokers (327.0 pg/mL) and non-smokers (295.0 pg/mL). In the regression model, passive smoking was independently associated with higher vitamin B12 concentrations (B=0.168, p = 0.027), while higher BMI was associated with lower concentrations (B=-0.011, p = 0.039). No significant correlation was observed between cotinine and vitamin B12 levels within any group. These findings suggest a possible compensatory metabolic response in passive smokers. Should these findings be validated, they could have clinical implications for evaluating vitamin B12 status in individuals exposed to tobacco smoke and highlight the urgency of enforcing smoke-free environments. Further investigation is needed to elucidate the mechanisms involved.