Interview with Giulia Collattuzzo, from University of Bologna (Italy). Dietary fiber intake may be associated with a lower risk of gastric cancer, with a protective effect that appears consistent across sex, tumor location and histological subtype. This is the key message emerging from a pooled analysis conducted within the STOP Consortium – Stomach Cancer Pooling Project, an international initiative launched in 2012 to investigate gastric cancer epidemiology through individual-level data from case-control and cohort studies.

In this interview, Giulia Collatuzzo explains how the analysis combined data from 11 studies including information on dietary fiber intake and major confounders. The statistical models were adjusted for several relevant factors, including sex, age, salt intake, smoking, socioeconomic status, and fruit and vegetable consumption. Helicobacter pylori infection was evaluated in secondary analyses on a subset of studies, due to missing data.

The results showed a dose-response association: for each quartile increase in dietary fiber intake, the risk of gastric cancer decreased by approximately 10%. This finding was confirmed in sensitivity and secondary analyses and remained consistent in both men and women, as well as in analyses stratified by cardia and non-cardia gastric cancer and by intestinal and diffuse histological types, with no statistically significant heterogeneity.

The interview also highlights the methodological complexity of nutritional epidemiology. The potential benefit of fiber may depend on several characteristics, including solubility, viscosity and fermentability, as well as on its interaction with the gut microbiome. At the same time, residual confounding remains possible, particularly because high fiber intake may occur in very different dietary contexts. When caloric intake was not included in the model, fiber appeared associated with increased risk, likely reflecting the fact that individuals with high overall energy intake may consume more fiber alongside unhealthy foods such as fatty foods, red meat and salt.

Overall, the findings support an independent protective association between dietary fiber and gastric cancer risk, while also suggesting that future research should clarify which types of fiber and which microbiome-mediated mechanisms may be most relevant for gastric protection.