text: BACKGROUND: Consumption of Plantago ovata may protect against colorectal cancer. To test this hypothesis, an ecological study was performed to determine mortality rates and distribution of colorectal cancer, and the consumption and distribution of P ovata, in different provinces in Spain. The putative association between P ovata consumption and mortality from colorectal cancer was then evaluated. METHODS: We conducted a comparative ecological study of Spanish provinces, with colorectal cancer mortality as the dependent variable and per capita consumption of P ovata by province and year as the independent variable. Associations were analyzed by calculating Spearman's correlation coefficients and a Poisson multiple regression model. RESULTS: Consumption of P ovata tended to be inversely correlated with mortality from colorectal cancer. In the Poisson regression analysis this tendency remained and reached statistical significance for the top quintile of P ovata consumption in the adjusted analysis (P = 0.042). CONCLUSIONS: Our results show an inverse trend between the consumption of P ovata and colorectal cancer mortality. We recommend additional observational studies of individuals, in order to better control confounding factors.