To examine the effects of dietary factor and Helicobacter pylori (H. pylori) infection with emphasis on vitamin intake on the risk of gastric cancer (GC), we conducted a case-control study in South Korea, a high-risk area for GC. Trained dietitians interviewed 136 cases histologically diagnosed with GC. An equal number of hospital controls was selected by matching sex and age.
High dietary intakes of vegetable fat [odds ratio (OR) = 0.35; 95% confidence interval (CI) = 0.15-0.83], folate (OR = 0.35; 95% CI = 0.13-0.96), and antioxidants, such as vitamin A (OR = 0.34; 95% CI = 0.13-0.83), β-carotene (OR = 0.33; 95% CI = 0.13-0.82), vitamin C (OR = 0.26; 95% CI = 0.09-0.72), and vitamin E (OR = 0.41; 95% CI = 0.17-1.01), were shown to have a protective effect on GC risk using a multivariate model adjusting for foods significantly related to GC in our previous study (charcoal grilled beef, spinach, garlic, mushroom, and a number of types of kimchi) and supplement use.
When stratified according to H. pylori infection, high intakes of vitamin C (OR = 0.10; 95% CI = 0.02-0.63) and vitamin E (OR = 0.16; 95% CI = 0.03-0.83) exhibited highly significant inverse associations with GC among the H. pylori-infected subjects compared with noninfected individuals. GC risk was significantly decreased only when consumption levels for two of these vitamins were high. Our findings suggest that high intake of antioxidant vitamins contribute to the reduction of GC risk and that GC risk in Korea may be decreased by encouraging those with H. pylori infection to increase their intake of antioxidant vitamins.