We conducted a population-based, double-blind, randomized controlled trial to examine the effect of vitamin C supplementation on serum pepsinogen (PG) level, Helicobacter pylori (H. pylori) infection, and cytotoxin-associated gene A (Cag A) status. Subjects aged 40 to 69 years living in one village in Akita prefecture, a high-risk area for gastric cancer in Japan, were recruited through annual health check-up programs. Among 635 subjects diagnosed as having chronic gastritis on the basis of serum PG levels, after excluding ineligible cases, 439 subjects were assigned to one of four groups using a 2×2 factorial design (0 or 15 mg/day β-carotene and 50 or 500 mg/day vitamin C).
However, based on the results from two β-carotene trials in the United States, we discontinued β-carotene (vitamin C supplementation was continued). Finally, 120 subjects in the low-dose group (vitamin C 50 mg), and 124 subjects in the high-dose group (vitamin C 500 mg) completed the 5-year supplementation. The difference in the change of PGI/II ratio between baseline and after 5-year follow up was statistically significant between the intervention groups among those who completed the supplementation: -0.25 for the low-dose group and -0.13 for the high-dose group (P=0.046). To conclude, vitamin C supplementation may protect against progression of gastric mucosal atrophy.