Association between Dietary Inflammatory Index (DII) and Risk of Breast Cancer: a Case-Control Study

Background: Breast cancer (BrCa) is the most common cancer among women worldwide and is the second leading cause of cancer-related death in women, in developed countries. This cancer is among the top five most common cancers in Iran. Studies have shown that dietary components are implicated in the etiology of BrCa. The existence of molecular connections between inflammation and BrCa has been demonstrated via different bimolecular events. Methods: We examined the ability of the dietary inflammatory index (DIITM) to predict the risk of BrCa. This included 145 cases and 148 controls, who attended the specialized centers. DII scores were computed based on dietary intake assessed using a 168-item FFQ. Logistic regression models were used to estimate multivariable ORs. Results: Modeling DII as a continuous variable in relation to risk of BrCa showed a positive association after adjustment for age and energy (OR=1.76; 95% CI=1.43-2.18); and were nearly identical in the multivariable analyses (OR=1.80; 95% CI=1.42-2.28). DII as tertiles, and adjusting for age and energy, subjects in tertile 3 had an OR of 6.94 (95% CI= 3.26-14.79; P-trend ≤0.0001) in comparison to subjects in tertile 1. After multivariable adjustment, results were essentially identical as in the model adjusting for age and energy (OR tertile 3vs1=7.24; 95% CI=3.14-16.68; P-trend ≤0.001). Sub group analyses revealed similar positive associations with HER 2 receptor +ve, progesterone receptor +ve, estrogen receptor +ve and lymph node invasive cases. Conclusion: Subjects who consumed a more pro-inflammatory diet were at increased risk of BrCa compared to those who consumed a more anti-inflammatory diet.