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 concentrations<20 ng/mL. Logistic regression models were used to assess the association of serum VD levels and H. 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+.