Inflammation may be important in endometrial cancer development. Long-chain ω-3 (n-3) polyunsaturated fatty acids (LCω-3PUFAs) may reduce inflammation and, therefore, reduce cancer risk. Because body mass is associated with both inflammation and endometrial cancer risk, it may modify the association of fat intake on risk.Objective:
We examined whether intakes of LCω-3PUFAs were associated with endometrial cancer risk overall and stratified by body size and histologic subtype.Design:
Women were n = 87,360 participants of the Women's Health Initiative Observational Study and Clinical Trials who were aged 50–79 y, had an intact uterus, and completed a baseline food-frequency questionnaire. After 13 y of follow-up, n = 1253 incident invasive endometrial cancers were identified. Cox regression models were used to estimate HRs and 95% CIs for the association of intakes of individual ω-3 fatty acids and fish with endometrial cancer risk.Results:
Intakes of individual LCω-3PUFAs were associated with 15–23% linear reductions in endometrial cancer risk. In women with body mass index (BMI; in kg/m2) <25, those in the upper compared with lowest quintiles of total LCω-3PUFA intake (sum of eicosapentaenoic, docosapentaenoic, and docosahexaenoic acids) had significantly reduced endometrial cancer risk (HR: 0.59; 95% CI: 0.40, 0.82; P-trend = 0.001), whereas there was little evidence of an association in overweight or obese women. The reduction in risk observed in normal-weight women was further specific to type I cancers.Conclusions:
Long-chain ω-3 intake was associated with reduced endometrial cancer risk only in normal-weight women. Additional studies that use biomarkers of ω-3 intake are needed to more accurately estimate their effects on endometrial cancer risk. This trial was registered at clinicaltrials.gov as NCT00000611.