There are geographic and ethnic differences in the incidence of gastric cancer around the world as well as with its trends for each population over time. The incidence patterns observed among immigrants change according to where they live. All of these factors serve to indicate the close association of gastric cancer with modify able factors such as diet. This review presents epidemiological evidence on the association between dietary factors and gastric cancer based on previous systematic reviews and subsequent updates. Infection with Helicobacter pylori is a strong and established risk factor of gastric cancer but is not a sufficient cause for its development. Substantial evidence from ecological, case-control, and cohort studies strongly suggests that the risk may be increased with a high intake of various traditional salt-preserved foods and salt per se and decreased with a high intake of fruit and vegetables, particularly fruit. However, it remains unclear which constituents in fruit and vegetables play a significant role in gastric cancer prevention. Among them, vitamin C is a plausible candidate supported by a relatively large body of epidemiological evidence. Consumption of green tea is possibly associated with a decreased risk of gastric cancer, although the protective effects have been, for the most part, identified in Japanese women, most of whom are nonsmokers. In contrast, processed meat and N-nitroso compounds may be positively associated with the risk of gastric cancer. Epidemiologic evidence on the relation between nutrition and stomach cancer is reviewed. Stomach cancer shows a distinct international variation and dramatic worldwide decline. These descriptive features suggest that dietary factors are important in determining the risk of stomach cancer. The authors assessed relevant data regarding specific dietary hypotheses in the etiology of stomach cancer. A negative association with fresh vegetables and fruits is highly consistent in numerous case-control studies in different populations. Both epidemiologic and experimental data suggest that vitamins C and carotenoids lower risk of stomach cancer. Evidence is sparse and inconsistent as to protective effects of vitamin E and selenium. Epidemiologic studies have not lent, and will not provide, supportive evidence for an etiologic role of nitrate intake. High salt intake has been associated with an increased risk in many case-control studies and limited cohort studies. Taken together with animal data, it is considered that high salt intake is a risk factor for stomach cancer. Both epidemiologic and experimental data are inconclusive as to whether high-starch diets confer an increased risk. Cohort studies using quantitative dietary assessment and biologic measurement of micronutrients are needed for further understanding of etiologic roles of dietary factors in the causation of stomach cancer. In conclusion, dietary modification by reducing salt and salted food intake, as well as by increasing intake of fruit and vitamin C, represents a practical strategy to prevent gastric cancer.
Key words :Stomach neoplasms · Diet · Salt · Helicobacterpylori · Fruit and vegetables · Epidemiological studies