EVALUATION OF THE ETIOLOGIC ROLE OF DIETARY SALT EXPOSURE IN GASTRIC AND OTHER CANCERS IN HUMANS

The findings in laboratory and epidemiological studies relevant to the assessment of salt for carcinogenic potential are reviewed. Associati ons between the high consumption of certain highly salted foodstuffs, particularly in some oriental countries, and increased risk of cancer of the stomach do not incriminate salt per se. Some highly spiced food s contain potent genotoxic carcinogens, irrespective of whether they a lso contain salt. There is evidence in laboratory animals that high co ncentrations of salt may increase the incidence of gastric cancer caus ed by such carcinogens. This may well be attributable to a marked and sustained regenerative response in the gastric mucosa of laboratory an imals chronically exposed to the cytotoxicity of hyperosmolar concentr ations of salt, such a mitogenic response favouring; the progression t owards neoplasia. However, there is no laboratory evidence whatsoever to indicate that salt per se is a carcinogen for any site in the body; neither is there any reliable epidemiological evidence to indicate th at dietary salt affects the incidence of gastric or other cancers. A p articular problem in the interpretation of epidemiological studies is that the consumption of diets containing highly salted, spicy foods is often associated with low intakes of fruit and green vegetables, whic h contain cancer-protective antioxidants. In Western countries the inc idence of cancer of the stomach has been falling for some 50 years. Th e consensus view is that this fall is attributable to improved food hy giene and increasingly available facilities for refrigeration. There a re no grounds for supposing that the fall is attributable to a decreas ing intake of salt. A high dietary salt intake does not necessarily en tail exposure to salt in concentrations high enough to damage the gast ric mucosa. The typical Western diet would not be expected to provide such high salt concentrations. It is concluded that there are no groun ds for believing that a reduction in the average daily salt intake in the Western diet would have any effect on the risk of developing any f orm of cancer. (C) 1997 Elsevier Science Ltd.