Gastric cancer is one of the most prevalent malignancies in Korea. The pathogenesis of gastric cancer, especially adenocarcinoma, includes increased cellular proliferation, increased free oxygen radical, decreased apoptosis, abnormalities of repair gene or overexpression of cyclooxygenase-2. Genetic damage by increased cellular proliferation and free oxygen radical goes to malignant change. Helicobacter pylori infection causes chronic gastritis known as a premalignant lesion. For prevention of gastric adenocarcinoma, it is necessary to avoid carcinogen. The long term ingestion of nitrates in salted, smoked foods seems to be related to a higher risk. Fresh vegetables and fruits appear to have chemopreventive effect for gastric adenocarcinoma. Vitamin A, C, E, carotenoids, selenium, soybean or green tea have potent antioxidant activity to prevent carcinogenesis. The effect of H. pylori eradication on the risk for gastric cancer is still under investigation.

Keywords: Gastric cancer, Adenocarcinoma, Chemoprevention, Genetic damage, Helicobacter pylori