NEW YORK (Reuters Health) - A salty diet may increase the risk of stomach cancer by 10 percent, South Korean researchers found in a study of more than 2 million people.

Makgeolli and tidbits are set at a bar in Seoul October 16, 2009. REUTERS/Lee Jae Won

They found a “weak but positive” association between a preference for salt and an increased risk of stomach cancer.

Although the mechanisms by which salt may be involved in the development of stomach cancer remain unclear, “restricting salt intake is thought to be beneficial for preventing gastric cancer,” Jeongseon Kim and colleagues from the National Cancer Center Research Institute in Goyang-si, South Korea, note in the American Journal of Clinical Nutrition.

Stomach cancer (or gastric cancer) is a major cancer in much of the world but not the United States. While gastric cancer is declining, it is still the most common cancer in Korea. Past studies have yielded conflicting results as to whether a salty diet causes gastric cancer, though most found an association between salt use and gastric cancer.

Kim and colleagues assessed the effect of salt preference in relation to gastric cancer in more than 2.2 million South Korean adults aged 30 to 80 years old. All of them provided information on diet and lifestyle and had health checkups between 1996 and 1997.

According to the Korea Central Cancer Registry, over the course of 7 years, 9,620 men and 2,773 women developed stomach cancer. According to Kim and colleagues, people who preferred salty diets had a 10 percent increased risk of developing gastric cancer.

Dr. Al B. Benson III, a gastric cancer specialist from Northwestern University’s Feinberg School of Medicine in Chicago, who was not involved in the study, said while the Korean findings are not definitive, they do support the long-suspected association between salt intake and gastric cancer.

He said how salt is consumed may be important. For example, he cited a Japanese study that found that sodium in the form of table salt posed risks for heart disease but not cancer, while salted foods, such as processed fish, were associated with cancer and not cardiovascular disease.

“The implication is that in areas where salt is used as a way to preserve foods, such as pickling, there is a higher risk,” Benson explained. “This link would make sense for Asian countries and Eastern Europe, including Russia in particular, where salting of foods has been a mainstay of the diet.”

Benson also noted that incidence of gastric cancer, while higher than in the United States, has been declining in Korea, due largely to changes in the diet and also in food preservation of methods, especially the use of refrigeration.

The same sort of decline in gastric cancer occurred in the United States decades ago.

“Gastric cancer was the leading cause of cancer death in the United States in the 1930s, but rates have dropped over time, probably due to a number of factors,” including declining rates of infection with Helicobacter pylori (a bacterium responsible for ulcers and stomach inflammation),” Dr. Eric Jacobs, of the American Cancer Society in Atlanta, who was not involved in the study, noted in an email to Reuters Health.

Gastric cancer no longer ranks among the 10 most common cancers in this country, Jacobs mentioned. Still, the American Cancer Society estimates that there were about 21,000 new cases of gastric cancer and 11,000 deaths from gastric cancer in the U.S. in 2009.

Should Americans cut back on salt to prevent gastric cancer? Marji McCullough, nutritional epidemiologist at the American Cancer Society, said, “It is not clear that reducing salt consumption would meaningfully reduce gastric cancer risk in U.S. populations. However, U.S. government guidelines recommend avoiding excessive salt intake in order to reduce risk of high blood pressure.”

Benson said immigrants might want to take a closer look at their dietary salt intake. “If you now live in the United States, although are originally from an area of the world with high gastric cancer rates, then you should look at your current diet and consider reduction of salted foods. Otherwise, for most of the U.S. population, (the Korean) study would not be relevant,” Benson noted.

SOURCE: American Journal of Clinical Nutrition, online March 10, 2010.