Numerous epidemiologic studies have shown that a diet high in salt is associated with an increased risk of gastric cancer. Timothy L. Cover and colleagues of Vanderbilt University have shown that high dietary salt combined with infection by the ulcer-causing bacterium Helicobacter pylori greatly increases the risk of cancer.
The study was published in the journal Infection and Immunity.
In the study, the researchers infected Mongolian gerbils with Helicobacter pylori. One set of gerbils received a regular diet; the other, a high salt diet. At the end of the experiment the researchers analyzed the animals' stomach tissues. Every animal on the high salt diet developed cancer, compared with just 58% of those on the regular diet.
It appears development of gastric cancer required the presence of a particular bacterial oncoprotein, known as CagA, which is produced by Helicobacter pylori.
Gastric cancer did not develop in animals on the high salt diet that were infected with a mutant Helicobacter pylori which did not produce CagA.
In earlier studies, Cover and others had shown that culturing Helicobacter pylori in a high salt environment boosts production of CagA.
The researchers noted that while no studies, to their knowledge, have examined relationships among a high salt diet, and infection with Helicobacter pylori expressing cagA, in several parts of the world that have high rates of gastric cancer, there is a high prevalence of cagA+ strains and a large proportion of the population consumes a high-salt diet.
The researchers also detected significantly higher levels of gastric inflammation in Helicobacter pylori-infected gerbils on a high salt diet than in those on a regular diet, a finding which Cover says is relevant to many types of cancer. They also showed that transcription of various inflammatory cytokines, such as interleukin 1-beta, are elevated in the former as compared to the latter, suggesting that these factors may contribute to the increased inflammation and increased gastric risk that accompany a high salt diet.
At least 50% of humans are infected with Helicobacter pylori, at least 90% of them without symptoms. ( Xagena )
Source: American Society for Microbiology, 2013