Why Japan and Korea Have So Much Stomach Cancer Despite Long Lives

Japan has the longest life expectancy in the world and historically low rates of colon, breast, ovarian, prostate, bladder, and blood cancers. It also has one of the highest rates of stomach cancer. Japanese men had about seven times less prostate cancer than Americans but about six times more stomach cancer. Korea shows a similar pattern. This matters for anyone who wants to extend healthspan, because it shows that a traditional diet can protect against some diseases while raising the risk of another.

The article works through the candidate explanations. An early theory blamed talc used to polish white rice, but it was not supported for stomach cancer. Genetics also falls short, since Japanese migrants and their children see stomach cancer rates fall as they adopt Western diets and lifestyles. H. pylori, a bacterial infection that causes chronic stomach inflammation, is a Group 1 carcinogen, and Korea and Japan have high infection rates. But the so-called African and Indian enigmas complicate the picture. India has about twice Japan's H. pylori prevalence yet roughly ten times less stomach cancer.

The proposed answer is a co-factor. Inflammation from H. pylori may make the stomach lining more vulnerable to dietary carcinogens. Studies comparing Asian populations with similar infection rates but very different cancer rates point to preserved, salted foods, both fish and vegetables. A review of 60 studies linked pickled food intake to significantly higher stomach cancer rates, more strongly in Korea, where per-capita intake of salt-fermented vegetables like kimchi is five to eight times higher. Fresh fruits and vegetables were associated with an 85% reduction in odds, while fresh fish showed no clear link either way. Pickled vegetable extracts also damaged DNA in lab cells.

In practice, the findings suggest eating plenty of fresh produce and limiting heavily salted, pickled foods, especially if you carry H. pylori or have a family history of stomach cancer. Testing for H. pylori and treating it is also a reasonable conversation to have with a doctor.

There are caveats. Most of the evidence is observational and can be confounded by overall diet, salt intake, and smoking. Lab DNA damage does not prove cancer in people. The excerpt is also cut off before the human testing is described.