Person:

Tabung, Fred

Background/objective The dietary inflammatory index (DII) measured at one time point is associated with risk of several chronic diseases but disease risk may change with longitudinal changes in DII scores. Data are lacking regarding changes in DII scores over time, therefore we assessed changes in the DII in the Women's Health Initiative (WHI). Methods: DII scores were calculated using data from repeated food frequency questionnaires in the WHI Observational Study (OS; n=76,671) at baseline and Year 3, and the WHI Dietary Modification trial (DM; n=48,482) at three time points. Lower DII scores represent more anti-inflammatory diets. We used generalized estimating equations to compare mean changes in DII over time, adjusting for multiple comparisons; and multivariable linear regression to determine predictors of DII change. Results: In the OS, mean DII decreased modestly from −1.14 at baseline to −1.50 at Year 3. In the DM, DII was −1.32 in Year 1, −1.60 in Year 3, and −1.48 in Year 6 in the intervention arm, and was −0.65 in Year 1, −0.94 in Year 3 and −0.96 in Year 6 in the control arm. These changes were modified by BMI, education, and race/ethnicity. A prediction model explained 22% of the variance in the change in DII scores in the OS. Conclusion: In this prospective investigation of postmenopausal women, reported dietary inflammatory potential decreased modestly over time. Largest reductions were observed in normal weight, highly educated women. Future research is warranted to examine whether reductions in DII are associated with decreased chronic disease risk.

Background: Diet modulates inflammation and inflammatory markers have been associated with cancer outcomes. In the Women's Health Initiative, we investigated associations between a dietary inflammatory index (DII) and invasive breast cancer incidence and death. Methods: The DII was calculated from a baseline food frequency questionnaire in 122 788 postmenopausal women, enrolled from 1993 to 1998 with no prior cancer, and followed until 29 August 2014. With median follow-up of 16.02 years, there were 7495 breast cancer cases and 667 breast cancer deaths. We used Cox regression to estimate multivariable-adjusted hazards ratios (HRs) and 95% confidence intervals (95% CIs) by DII quintiles (Q) for incidence of overall breast cancer, breast cancer subtypes, and deaths from breast cancer. The lowest quintile (representing the most anti-inflammatory diet) was the reference. Results: The DII was not associated with incidence of overall breast cancer (HRQ5vsQ1, 0.99; 95% CI, 0.91–1.07; Ptrend=0.83 for overall breast cancer). In a full cohort analysis, a higher risk of death from breast cancer was associated with consumption of more pro-inflammatory diets at baseline, after controlling for multiple potential confounders (HRQ5vsQ1, 1.33; 95% CI, 1.01–1.76; Ptrend=0.03). Conclusions: Future studies are needed to examine the inflammatory potential of post-diagnosis diet given the suggestion from the current study that dietary inflammatory potential before diagnosis is related to breast cancer death.