However, the American Cancer Society lists the following dietary risks, and protective factors, for stomach cancer: "smoked foods, salted fish and meat, and pickled vegetables (appear to increase the risk of stomach cancer.) Nitrates and nitrites are substances commonly found in cured meats. They can be converted by certain bacteria, such as H pylori, into compounds that have been found to cause stomach cancer in animals. On the other hand, eating fresh fruits and vegetables that contain antioxidant vitamins (such as A and C) appears to lower the risk of stomach cancer." A December 2009 article in American Journal of Clinical Nutrition found a statistically significant inverse correlation between higher adherence to a Mediterranean Dietary Pattern and stomach cancer.

In more detail, H. pylori is the main risk factor in 65–80% of gastric cancers, but in only 2% of such infections. Approximately ten percent of cases show a genetic component. In Japan and other countries bracken consumption and spores are correlated with incidence of stomach cancer, though causality has yet to be established.