Dietary patterns and gastric cancer in a Portuguese urban population

Dietary patterns analysis is a powerful technique to study the relations between diet and cancer. We aimed to quantify the association between dietary patterns and gastric cancer, by location and histological type, according to Helicobacter pylori infection status. We analyzed 591 incident cases of gastric adenocarcinoma and 1,463 community controls. Dietary intake was assessed using a validated food frequency questionnaire. Principal components and cluster analyses were used to define dietary patterns. Anti-H. pylori IgG was assessed by ELISA. Age-, gender-, education- and total energy intake-adjusted odds ratios (OR) were computed. Three dietary patterns were identified, with the following main characteristics: (I) high consumption of fruits and dairy products, and low consumption of alcoholic beverages; (II) low consumption of fruit, salads, vegetables, dairy products, fish and meat; (III) high consumptions of most food groups and low vegetable soup intake. Compared to pattern I, the risk of gastric cancer was higher for pattern II (OR = 1.68, 95% CI: 1.31-2.14) but not for pattern III (OR = 0.80, 95% CI: 0.57-1.14), with no effect modification by H. pylori infection. The association was similar for cardia and non-cardia gastric cancer, but for tumors of the diffuse Laurén histological type, the association was weaker for pattern II vs. I (OR = 1.32, 95% CI: 0.83-2.08) and a protective effect was observed for pattern III vs. I (OR = 0.43, 95% CI: 0.22-0.87). Our results confirm the protective effect of high fruit and vegetables intake, and show a differential association according to histological type. No effect modification by H. pylori infection was observed.