Scope: Diet in relation to breast cancer etiology has been studied widely, but results have remained inconsistent. Various dietary components including fruits, vegetables, and meat have been implicated through their effects on inflammation. Using data from the Iowa Women's Health Study we examine prospectively the association between the dietary inflammatory index (DII) and breast cancer incidence. Methods and results: DII scores were computed based on baseline dietary intake assessed by a validated 121-item food frequency questionnaire in a cohort of 34 700 women, aged 55–69 years at recruitment in 1986 and followed for incident breast cancer. During the 25-year follow-up period (1986–2011), 2910 incident breast cancer cases were identified. We used Cox proportional hazards regression to estimate multivariable hazard ratios (HRs) and 95% confidence intervals (CI). We found positive associations between DII scores and breast cancer risk (HR for DIItertiles: T3 vs T1 = 1.11; 95% CI: 1.00, 1.22), with stronger associations in obese women (HR for DIIcontinuous: 1.05 per unit increase in DII; 95% CI: 1.02, 1.12; HR for DIItertiles: T3 vs T1 = 1.35; 95% CI: 1.10, 1.66, p-value for interaction = 0.02). Conclusion: A proinflammatory diet, as indicated by higher DII scores, appears to increase the risk of developing breast cancer, especially in obese postmenopausal women.
Bibliographical noteFunding Information:
This study was supported by National Cancer Institute grant R01 CA39742. A.E.P. was supported by the National Center for Advancing Translational Sciences of the National Institutes of Health Award Number UL1TR000114. N.S. and J.R.H. were supported by grant number R44DK103377 from the United States National Institute of Diabetes and Digestive and Kidney Diseases. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health. The authors? contributions were as follows: C.K.B., A.E.P., and D.R.J. designed and conducted the study, C.K.B. created the data set for analyses, N.S. calculated DII and conducted all analyses and wrote the first draft of the manuscript, J.R.H., C.K.B., A.E.P., and D.R.J. provided suggestions and revised the manuscript. All authors approved the final version of the manuscript. J.R.H. owns controlling interest in Connecting Health Innovations LLC (CHI), a company planning to license the right to his invention of the dietary inflammatory index (DII) from the University of South Carolina in order to develop computer and smart phone applications for patient counseling and dietary intervention in clinical settings. N.S. is an employee of CHI. D.R.J. is a consultant to the California Walnut Commission.
- Breast cancer