Fiber intake and risk of adenocarcinomas of the esophagus and stomach.

BACKGROUND: Since the 1970s, incidence rates for esophageal and gastric cardia adenocarcinomas have risen substantially for reasons that are not well understood. We sought to determine the role of dietary factors in these tumor types.
METHODS: This analysis on dietary factors included 206 esophageal adenocarcinoma, 257 gastric cardia, 366 distal gastric adenocarcinoma patients and, 1,308 control subjects from a population-based, case-control study conducted in Los Angeles County. Polytomous logistic regression was used to calculate odds ratios (ORs), as an estimate of the relative risk, and corresponding 95% confidence intervals (CIs) for the three tumor types.
RESULTS: Intake of fiber had a significant impact on risk of esophageal and gastric cardia adenocarcinoma after adjustment for age, gender, race, birthplace, education, cigarette smoking, body size, history of reflux, and vitamin use. Compared to subjects in the lowest quartile of fiber intake, subjects in the highest quartile of intake showed odd ratios of 0.44 (95% CI = 0.26-0.76) for esophageal adenocarcinoma (P trend = 0.004) and 0.58 (95% CI = 0.38-0.88) for gastric cardia adenocarcinoma (P trend = 0.016); these inverse associations remained after further adjustment for intake of fat. Positive associations between dietary fat and the three tumor types weakened after adjustment for fiber intake and were no longer statistically significant. For distal gastric cancer, a significant inverse association with fiber was observed only after adjustment for fat intake. The significant inverse associations with fiber remained after further adjustment for H. pylori infection for all three tumor types.
CONCLUSIONS: High intake of fiber was associated with significant reduced risks of esophageal and gastric cardia adenocarcinoma even after adjustment for dietary fat, H. pylori infection and other covariates.