Bladder cancer (BC) is the ninth recurrent neoplasm in the world. In Iran, incidence of BC is the third most common among men. Few dietary patterns are related to reduced carcinogenesis and consequently are amenable to modification in order to reduce the BC risk. Adherence to the traditional Nordic diet, as measured by the Healthy Nordic Food Index (HNFI), have shown a beneficial effect on chronic disease prevention, including cancer. The principal objective of this study was to investigate the association between HNFI and the odds of BC in a case-control study, in Iran.

The present case-control study was performed on 100 eligible cases and 200 controls of patients ≥45 years old referred to three referral hospitals in Tehran. Dietary intakes are assessed by a valid 168-item food frequency questionnaire (FFQ). The relationship between HNFI and BC is estimated using the logistic regression tests.

The average age of cases and control were 65.41 and 61.31 years, respectively. After controlling for potential confounders (age, smoke, total energy, and sex), participants in the highest tertile of HNFI (compared to the lowest tertile) have 83% lower BC risk (OR = 0.17; 95%CI = 0.07-0.42). Based on an independent assessment of HNFI component and BC risk, a significant negative association was observed for fish intake (OR = 0.30; 95%CI = 0.15- 0.60) and whole-grain bread intake (OR = 0.33; 95%CI = 0.17-0.63).

The findings of this study suggested that adherence to traditional Nordic diet could decrease the risk of BC. Of the elements of this diet, fish and whole-grain bread consumption seemed to decrease the odds of BC. Such findings ought to be considered in the development of evidence-base intervention for BC prevention in the country.