The relationship between dietary patterns, dietary quality index, and dietary inflammatory index with the risk of all types of cancer: Golestan cohort study

Background: Dietary patterns and diet quality index (DQI) are widely discussed in relation with different health conditions and have recently been taken into consideration for all cancer types. Since chronic inflammation has been recognized as an important biologic risk factor for cancer occurrence, especially in epithelial tissues, proinflammatory or anti-inflammatory characteristics of diet has become the center of attention. In the present study, we aimed to identify whether a specific dietary pattern, Mediterranean dietary score (MDs), and dietary inflammatory index (DII) were associated with overall cancer risk in Iranian population. Methods: This study was performed in the context of the Golestan cohort study. Participants with extreme daily energy intake or those who did not answer more than 30 question of the Food Frequency questionnaire (FFQ) were excluded. Dietary patterns, MDs, and DII were measured from FFQ. Age, sex, total energy, place of residence, smoking, wealth score, ethnicity, opiate use, BMI, education, marital status, and physical activity score were considered as confounding variables. Using Cox proportional hazards regression models, hazard ratios (HRs) and 95% confidence interval of cancer were estimated. Results: HRs (95% CIs) of all cancers by quartiles of Western dietary pattern, DII, and MDs showed that the forth quartile of the Western dietary pattern is attributed to 23% higher cancer risk (HRs: 1.23, CI: 1.09-1.40, P< 0.001, adjusted for age and sex) compared to the first quartile. It also remained significant after further adjustments (HRs = 1.20, CI: 1.06-1.36, P< 0.001). There was a higher cancer risk in the fourth quartile of DII in comparison with the first quartile (HRs = 1.16, CI: 1.01-1.32, P trend < 0.001, adjusted for age and sex). The lower adherence to the Mediterranean dietary pattern also largely contributes to 27% higher cancer risk (HRs: 1.27, CI: 1.12-1.44), P trend < 0.001, adjusted for age and sex), which also remained remarkable after further adjustments ((HRs =1.19, CI: 1.05-1.35, P trend < 0.001). Conclusion: Cancer is highly correlated to dietary intake and dietary patterns, such as the Western dietary pattern, while the Mediterranean diet score was inversely associated with cancer risk. Further investigations are required to get a broader insight into cancer determinants in population.