Gastric (stomach) cancer is second only to lung cancer in worldwide cancer deaths. The geographic distribution is exceptional: rates are low in the United States and Europe, but almost as high as those of lung cancer in eastern Asia. Dr. Mitsuru Sasako and coworkers in Japan reported that the most important risk factor is infection with Helicobacter pylori (H. pylori). Genetic susceptibility, smoking, and diets rich in salt but poor in vegetables are additional risk factors.
However, the number of cases of gastric cancer in Poland has been cut in half over the last 50 years, despite an unusually high rate of H. pylori infection. Dr. Miroslaw Jarosz and coworkers reported that 85 to 95 percent of Polish residents over age 25 years still experience H. pylori infection. The diet of this population, on the other hand, has changed dramatically since 1960.
Refrigerators have made the difference in the Polish diet. In 1960, there were only 1.8 refrigerators per 100 households. The diet at that time contained large amounts of salt-preserved meat, and very low amounts of fruits. By 1980 more than 90 percent of households had their own refrigerators. During the period 1990 – 2006, fruit consumption increased significantly, while there was a marked decrease in red meat and dairy products. Over the period from 1960 – 2006, there was a smaller but still significant increase in vegetable consumption.
Jarosz and coauthors obtained data on gastric cancer rates and food consumption for individual years between 1960 and 2006. Their paper included plots of gastric cancer incidence versus fruit consumption, vegetable consumption, and vitamin C consumption. The authors analyzed vitamin C in particular because lab studies show that this nutrient inhibits the growth of H. pylori, and destroys free radicals produced during infection. There is clear correlation between decreased cancer rates and increased fruits, vegetables, and vitamin C.
Other studies cited by Jarosz and coauthors have not shown such a large effect of diet on gastric cancer rates. Poland may be a particular case, Jarosz noted, because of its high rates of H. pylori infection and smoking.