Causes of stomach cancer (gastric cancer)

Dietary differences are thought to predispose to gastric cancer: thus, a high intake of complex carbohydrates, nitrates or salt and a low intake of animal fat, protein and salads, fruit and vegetables – all predispose on the available epidemiological evidence. The mechanism of this dietary predisposition is of interest and some speculation: When the acidity of the stomach rises, for whatever reason, bacteria survive which would ordinarily have succumbed due to the low pH. These bacteria chemically reduce nitrates in the diet to nitrites through nitrosation of the dietary amines; these are regarded as carcinogens or co-carcinogens. With regard to protection by fruit and vegetables, it is regarded that ascorbic acid and others may raise the pH and counteract the above process. Advancing age is another predisposing factor; for example, only 2% of cases occur before the age of 30 years of age. The presence of chronic gastritis is another predisposing factor, probably not entirely unrelated to the age factor. The presence of chronic gastritis, par excellence in the disease called pernicious anaemia, is a well recognised predisposing condition for the development of gastric cancer. Stomach infection with Heliobacter pylori is now recognised to be associated with a higher risk of gastric cancer through its causation of a chronic gastritis – the increase in risk in sufferers of this infection for a prolonged time is around six-fold. Once diagnosed the Heliobacter infection is readily eradicated by simple antibiotic therapy. Another infective agent viz. Epstein Barr virus (EBV) has also been linked to a higher incidence of the disease but the link is lees securely established at present.