Prebiotics and the risk of upper digestive tract and stomach cancers: the PrebiotiCa study

Background: Fiber intake may lower digestive tract cancer risk, possibly by modulating the composition of gut microbiota. However, no data is available about the role of specific fiber fractions with prebiotic activity, e.g., inulin-type fructans (ITFs), fructo-oligosaccharides (FOSs) and galactooligosaccharides (GOSs), on the risk lower digestive tract cancer. Objective: The objective was to assess the association between prebiotic intake and the risk of cancers of the upper digestive tract and stomach. Design: Within the PrebiotiCa study, data were derived from a network of Italian case-control studies conducted between 1992 and 2009. Participants' usual diet was assessed using a food frequency questionnaire (FFQ). ITFs, and selected FOSs (nystose, kestose and 1F-β-fructofuranosylnystose) and GOSs (raffinose and stachyose) were quantified in several food products via laboratory analyses. Participants' prebiotic intake was calculated by multiplying FFQ intake by the prebiotic content of each food item. Participants/setting: Cases were patients admitted to major hospitals with incident histologically confirmed cancers; there were 946 cases of cancer of the oral cavity/pharynx, 198 of the nasopharynx, 304 of the esophagus, 230 of the stomach. Over 4,000 patients admitted to the same hospitals for acute non-neoplastic nor diet-related conditions were selected as controls. Main outcome measures: The outcomes were oral and pharyngeal, nasopharyngeal, esophageal and stomach cancers. Statistical analyses performed: The odds ratios (OR) and corresponding confidence intervals (CI) of the various cancers were derived using logistic regression models adjusted for major confounders and energy intake. Results: No association was observed between the intake of prebiotics and the risk of cancers of the oral cavity and pharynx, nasopharynx and esophagus. High raffinose intake reduced stomach cancer risk (OR for the third versus the first tertile 0.6, 95% confidence interval, CI: 0.3-0.9); no other prebiotic was associated with stomach cancer. Conclusions: The current study does not support a major role of prebiotic fibers on selected upper digestive tract cancers. The association between high raffinose intake and reduced stomach cancer risk needs further investigation in future studies.