Dietary factors and the etiology of gastric cancer.

We have developed the working hypothesis that gastric cancer in man may result from the in vivo nitrosation in the stomach of as yet unknown substrates, with the production of alkylinitrosamides. We have established that a source of the nitrite required for the nitrosation was the reduction of nitrate in foods. Nitrate could be derived from its deliberate addition to food as a preservative, from drinking water, and from foods grown in nitrate-rich soils. The reduction of nitrate does not occur at 2-4 degrees, accounting for the decline in gastric cancer in countries and regions where means of refrigerated food storage have been introduced. Future research includes the search for the substrates, presumably in the form of alkylamides, in some foods typically consumed in high-risk regions.