Plasma free radical activity and antioxidant vitamin levels in dyspeptic patients: Correlation with smoking and Helicobacter pylori infection

Background. The pathological processes by which Helicobacter pylori infection leads to the development of gastroduodenal disease are still incompletely understood. Oxygen-derived free radicals are important mediators of inflammation and potential carcinogens. Furthermore, dietary studies have suggested that antioxidant vitamins may protect against gastric cancer. Objective. To determine plasma free radical activity and antioxidant vitamin levels in dyspeptic patients and to correlate the results with H. pylori infection and tobacco smoking. Subjects. Forty-three patients undergoing routine endoscopy for investigation of dyspepsia. Methods. Plasma free radical activity was determined by measurement of thiobarbituric acid-reactive substances (TBARS). Plasma samples were also assayed for the antioxidant vitamins A, C and E. Gastroduodenal biopsies were obtained from all patients for histological examination. Results. Plasma TBARS levels were significantly higher in H. pylori positive versus negative subjects (P < 0.03), smokers versus non-smokers (P < 0.04) and males versus females (P < 0.01). Multiple regression analysis revealed that after correcting for male sex and smoking there was no significant association between plasma free radical activity and H. pylori infection. Smokers had significantly lower levels of plasma vitamin C than non-smokers (P < 0.05); no differences were seen in vitamin A and E levels. Gender and H. pylori infection did not significantly affect plasma antioxidant vitamin levels. Gastroduodenal disease was present in all of the smokers compared with 67% of the non-smokers (P < 0.05); 69% of the smokers were H. pylori positive versus 53% of the non-smokers. Conclusions. Tobacco smoking and male sex, both recognized risk factors for gastroduodenal disease, appear to be the major determinants of increased plasma free radical activity in dyspeptic subjects, rather than H. pylori infection. The reason for the higher prevalence of H. pylori infection and gastroduodenal disease in dyspeptic smokers is unclear but may relate to weakened antioxidant defences.