Association between serum vitamin D levels and Helicobacter pylori cytotoxic-associated gene A seropositivity: a cross-sectional study in US adults from NHANES III

Objective To assess the association of serum vitamin D (VD) levels and Helicobacter pylori (H. pylori) cytotoxic-associated gene A (CagA) seropositivity, and further explore potential effect modifiers in this association. Design Cross-sectional study. Setting Data from phase I of the National Health and Nutrition Examination Survey (NHANES III, 1988-1991) led by the Center for Disease Control and Prevention. Participants A total of 3512 US adults (>= 20 years) with both serum VD levels and H. pylori CagA antibody data from NHANES III were included in the analysis. Methods VD deficiency was defined as serum 25(OH)D concentrationsH. pylori CagA seropositivity (VD-Hp CagA+), and stratification analyses were used to explore potential effect modifiers. Results There was no significant association of VD-Hp CagA+ in the general population. But serum 25(OH)D concentrations were associated with H. pylori CagA+ in non-Hispanic whites (adjusted OR=1.02, 95% CI: 1.00 to 1.03), other races/ethnicities (adjusted OR=1.08, 95% CI: 1.01 to 1.06), populations born in other countries (adjusted OR=1.09, 95% CI: 1.04 to 1.15) or occasional drinkers (adjusted OR=0.93, 95% CI: 0.88 to 0.99). VD deficiency was associated with H. pylori CagA+ in non-Hispanic whites (adjusted OR=0.69, 95% CI: 0.53 to 0.92), populations born in other countries (adjusted OR=0.47, 95% CI: 0.25 to 0.89), non-drinkers (adjusted OR=0.80, 95% CI: 0.65 to 0.99), occasional drinkers (adjusted OR=2.53, 95% CI: 1.06 to 6.05), population with first quartile level of serum ferritin (adjusted OR=0.70, 95% CI: 0.51 to 0.96) or fourth quartile level of serum folate (adjusted OR=0.63, 95% CI: 0.46 to 0.87). Conclusions Racial/ethnic differences and different serum ferritin or serum folate levels may be effect modifiers for the association of VD-Hp CagA+.