A species of bacteria that has been linked to both peptic ulcers and gastric cancer becomes more virulent in the presence of higher salt concentrations, according to a study presented at the conference of the American Society for Microbiology.

A bacteria known as Helicobacter pylori is believed to cause more than 75 percent of all peptic ulcers, including up to 80 percent of gastric ulcers and up to 90 percent of duodenal ulcers. However, the presence of H. pylori in the stomach does not always lead to ulcers or other noticeable health problems.

Researchers monitored the way that H. pylori genes expressed themselves under laboratory conditions, as well as the bacteria's rate of growth. They found that higher concentrations of salt caused the bacteria's growth rate to drop and caused its shape to change. Under these conditions, two genes linked to the organism's virulence were expressed more strongly.

This means that in the presence of salt, H. pylori is more likely to produce proteins that cause it to be more dangerous to humans, and more likely to produce ulcers.

"Apparently H. pylori closely monitors the diets of those people whom it infects," said lead researcher Dr. Hanan Gancz of the Uniformed Services University of the Health Sciences in Bethesda, Maryland. "We think that when there are high levels of salt in the stomach environment, H. pylori over-produces [the factors that] enable it to survive, which in the long term increases the risk of illness."

Gancz also noted that doctors have long been aware of a link between high salt intake and increased risk of gastric cancer. There is also a connection between H. pylori and gastric cancer risk, although it is not clear if the relationship is causal or not. Nevertheless, the International Agency for Research on Cancer has classified the bacteria as a carcinogen. Scientists have speculated that it may increase the production of free radicals and cell mutation in its host's body, or that it might induce local inflammation.

However, this research did not consider the differences between processed salt (sodium chloride) and full-spectrum sea salt (like Celtic sea salt). It may be that only processed salt causes this change in the bacteria while sea salt does a better job of protecting humans.