Association between the dietary inflammatory index and breast cancer in a large Italian case-control study.

INTRODUCTION: The putative relationship between diet, including its inflammatory potential, and breast cancer has been studied extensively, but results remain inconsistent. Using data from a large Italian case-control study conducted between 1991 and 1994, we examined the association between the dietary inflammatory index (DII) and odds of breast cancer.

METHODS: DII scores were computed using a validated 78-item food frequency questionnaire. Subjects were 2569 women with incident, histologically confirmed breast cancer and 2588 controls admitted to hospital for acute, non-hormone-related diseases. Odds ratios (ORs) and 95% confidence intervals (CIs) based on continuous and quintiles of DII were estimated by multiple logistic regression adjusting for age, study center, education, BMI, parity, menopausal status, family history of hormone-related cancers, and total energy intake.

RESULTS: Women in quintiles 2, 3, 4 and 5 had ORs of breast cancer of 1.33 (95% CI: 1.11, 1.59), 1.37 (95% CI: 1.13, 1.66), 1.41 (95% CI: 1.15, 1.73), and 1.75 (95% CI: 1.39, 2.21), respectively, compared to women in quintile 1. One-unit increase in DII increased the odds of having breast cancer by 9% (95% CI: 1.05, 1.14).

CONCLUSIONS: A pro-inflammatory diet is associated to increased risk of breast cancer.