H. pylori infection is recognized to lower the concentration of vitamin C in gastric juice. The objective of this study was to assess whether this effect of the infection on intragastric vitamin C resulted in reduced bioavailability of the ingested vitamin.

Methods: The study involved 1106 men and women aged 25–74 randomly recruited from the population of north Glasgow. Their H. pylori status was determined by measuring serum IgG antibody titres toH. pylori using a validated ELISA (Bio-Rad Laboratories Ltd., England). Dietary vitamin C intake was calculated from a food frequency questionnaire. Plasma vitamin C concentrations were measured by a fluorometric assay. Correction was made for potential confounding factors such as age, sex, smoking and social status.

Results: Sixty three percent wereH. pylori seropositive. The mean plasma vitamin C concentration in those who were H. pyloripositive was only 65% of that in those classified negative (p<0.0001). This was partly explained by the fact that the dietary intake of vitamin C of the H. pyloripositives was only 86.5% of that of the negatives (p<0.0001). Correction for the reduced dietary intake and other potential confounding factors included age, sex, social class and smoking still gave a plasma vitamin C level for H. pyloripositives which was only 80% of that for the H. pylori negatives (p<0.0001).

Conclusions: H. pylorisubstantially impairs bio-availability of vitamin C. This, together with the reduced vitamin C intake of H. pylori positive subjects markedly reduces the plasma vitamin C level of infected subjects. The reduced circulating levels of vitamin C in H. pylori infected subjects may contribute to the aetiology of gastric cancer, as well as other diseases associated with antioxidant deficiency.