Comparative epidemiological studies with ecological and case-control approaches in high-and lowepidemic areas of China have provided us with much evidence with regard to risk and benefit in the environment. To clarify how dietary factors are involved in esophageal and stomach cancer development, we performed a case-control study in a low-epidemic area, and compared the findings with those obtained earlier for a high-epidemic area for stomach cancer in the same Jiangsu Province, China. We recruited 199 and 187 cases with esophageal and stomach cancers, respectively, and 333 population-based common controls. Odds ratios (ORs) for esophageal and stomach cancers were calculated with adjustment for potential confounding factors, using an unconditional logistic model. Current and former smoking elevated the OR for esophageal cancer, along with high intake of pickled vegetables and broiled meat, while decreased ORs were observed for frequently consumed raw vegetables and garlic. With regard to stomach cancer, ORs were increased with frequent consumption of salty fish, leftover gruel, and broiled meat, and lowered by snap bean consumption. The present risk factors were common to the previously obtained results in the high-epidemic area, and similarly distributed in each general population. While more protective factors were observed in the high-epidemic area, their penetrance was much greater in the lowepidemic area. The present study thus suggests that frequent vegetable and garlic consumption contributes to low mortality rates for esophageal and stomach cancers in a low-epidemic area, counteracting similar exposure levels for risk factors as in the high-epidemic area.
Key words: Dietary factors -Stomach cancer -Esophageal cancerEast Asia is a region of the world where stomach cancer is epidemic 1) but there is considerable geographical variation and mortality rates also differ greatly at the provincial level in China.2) Dietary factors are considered to be major contributors in this respect and previous studies have shown a positive association between increased risk for stomach cancer, and income, occupation, smoking, mental injury, overeating, high consumption of salt, dietary carbohydrates, sweet potatoes, sour pancakes, salted and fermented soya paste, fermented staple, leftover gruel and pickled vegetables, and low consumption of animal protein in China.3-10) Decreased risk has been reported with frequent consumption of allium and other vegetables. 4,9,11) Most of these risk and protective factors appear to act in common for esophageal cancer, 9,12) and geographical variation in high-epidemic areas in China is also similar for neoplasms of both these organ sites.
2)Comparative ecological studies between high-and lowepidemic regions can yield valuable information, especially when the level of exposure to specific environmental factors is common to people living in one area and very different from that in the other. We have found such highand low-epidemic areas for stomach cancer in Jiangsu Province, China,13) and ...
