The role of diet and other environmental factors in the causation of gastric cancer in Iran--a population based study.

Despite a declining trend in the incidence of gastric cancer (GC), it is still a major global public health concern of the 21st century. The rates of GC reported from Ardabil Province, Iran, are among the highest in the world. To investigate risk factors for GC in Ardabil, we undertook a population-based case-control study. The study aimed to recruit all Ardabil residents newly diagnosed with GC in the time period of 2004-2005, and 2 controls per case. Participants were interviewed using a structured questionnaire. Ten milliliters of blood was collected for blood grouping and investigating the presence of IgG antibodies against Helicobacter pylori. During the study period, 217 people with GC and 394 controls were recruited. In multivariate analysis, diet and Helicobacter pylori infection (OR = 2.41; 95% CI: 1.35-4.32) were found to be the factors that were most strongly related to GC. High intake of Allium vegetables (OR = 0.35) and fruit, especially citrus fruit (OR = 0.31) and consumption of fresh fish (OR = 0.37) were significantly protective. On the other hand, consumption of red meat (OR = 3.40) and dairy products (OR = 2.28) were positively associated with the risk of GC. People who had a preference for higher salt intake (OR = 3.10) and drinking strong and hot tea (OR = 2.64 and 2.85, respectively) were at higher risk. In conclusion, Helicobacter pylori infection as measured by serum IgG as well as the consumption of red meat and dairy products increases the risk of GC in Ardabil, while the intake of fresh fruit and fresh fish decrease the risk.