Effect of dietary vitamin C on gastric cancer risk in the Korean population

AIM: To investigate the effects of dietary vitamin C and foods containing vitamin C on gastric cancer risk.METHODS: Our study included 830 control subjects and 415 patients. Data regarding demographics, medical history, and lifestyle, including dietary and nutrient intake, were collected using reliable selfadministered questionnaires. Dietary intake information was collected from the participants using a food frequency questionnaire that has been previously reported as reliable and valid. A rapid urease test and a histological evaluation were used to determine the presence of Helicobacter pylori(H. pylori) infection. Twenty-three vitamin C-contributing foods were selected, representing over 80% of the cumulative vitamin C contribution. RESULTS: In analyses adjusted for first-degree family history of gastric cancer, education level, job, household income, smoking status, and regular exercise, an inverseassociation between vitamin C intake and gastric cancer risk was observed for the highest(≥ 120.67 mg/d) vs the lowest(< 80.14 mg/d) intake category [OR(95%CI): 0.64(0.46-0.88)], with a significant trend across the three intake categories(P = 0.007). No protective effect of vitamin C was detected after stratification by gender. No effect of vitamin C intake on the gastric cancer incidence was found in either men or women infected with H. pylori. Vitamin C-contributing foods, including cabbage [0.45(0.32-0.63), 0.50(0.34-0.75), 0.45(0.25-0.81)], strawberries [0.56(0.40-0.78), 0.49(0.32-0.74), 0.52(0.29-0.93)], and bananas [0.40(0.29-0.57), 0.41(0.27-0.62), 0.34(0.19-0.63)], were protective factors against the risk of gastric cancer based on the results of the overall adjusted analyses and the results for men and women, respectively.CONCLUSION: A protective effect of vitamin C and vitamin C-contributing foods against gastric cancer was observed. Further studies using larger sample sizes are required to replicate our results.