Adherence to Mediterranean style dietary pattern and cancer risk in the Framingham Offspring cohort study
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BACKGROUND: The benefits of the Mediterranean-style dietary pattern in mitigating cancer risk among Americans is unclear and its role in obesity-related cancer risk has not been evaluated. OBJECTIVES: This study examines the prospective association between adherence to a Mediterranean style dietary pattern and cancer risk (including total, obesity related, breast and colorectal cancers) among men and women in the Framingham Offspring (FOS) cohort. In secondary analyses for breast cancer, we explore stratifying by hormone receptor status and menopausal status. METHODS: The Mediterranean style dietary pattern (MSDP) score was derived from a semi-quantitative food frequency questionnaire taken at examination visit 5 in the prospective FOS cohort. Subjects included 3199 participants (1703 women and 1496 men), aged 30 years old and older, who were free of prevalent cancer. The MSDP score was classified into tertiles and also dichotomized (MSDP score <19 vs. ≥19) to evaluate the association between the MSDP and cancer risk through the ninth examination cycle (2014). Cox proportional-hazards regression models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for all subjects and for men and women separately, adjusting for confounding by age, physical activity, body mass Index, pack-years of cigarette smoking, supplement use, diabetes status and sex (for all subjects models). In the breast cancer model, we adjusted for age, waist-to-height ratio height ratio, pack-years, physical activity, diabetes, supplement use age at menopause. Factors found not to confound the effects of the MSDP on cancer risk were excluded from final models. RESULTS: During a median follow-up of approximately 18 years, 377 and 273 cancer cases were documented among men and women, respectively. Women in the upper two tertiles of the MSDP score had approximately 30% lower lower total cancer risks than women in the lowest tertile (tertile 2: HR, 0.69, 95% CI: 0.50-0.94; tertile 3: HR, 0.73; 95% CI: 0.54-0.99). Effects in men were weaker. Higher adherence to a MSDP was somewhat more strongly protective against total cancer risk among lower-risk individuals such as those who were leaner (BMI <25), drank less alcohol (<14 g/d), and did not currently smoke cigarettes. The association between MSDP adherence and total cancer risk was also modified by waist circumference and WHtR. We also observed a non-statistically significant protective effect of higher MSDP conformity and obesity-related cancer risk (tertile 3: HR, 0.80, 95% CI: 0.60-1.07). The association was present especially among women (tertile 2: HR, 0.76, 95% CI 0.53-1.09; tertile 3: HR, 0.73, 95% CI: 0.51-1.05). In analyses of effect modification by anthropometric measures of body fat, the combined effect estimates for higher adherence to the MSDP in women and body fat were more than additive for BMI and WHtR. The MSDP adherence was also inversely associated with BrCa risk (tertile 3 vs tertile 1: HR: 0.58, 95% CI: 0.34-0.98) especially in post-menopausal women (HR: 0.51, 95% CI: 0.29-0.91) and among those with any positive Estrogen Receptor/Progesterone Receptor BrCa (HR: 0.58, 95% CI: 0.31-1.06). We found no association between MSDP and colorectal cancer in these analyses. CONCLUSIONS: In this large cohort study, higher adherence to MSDP was associated with lower cancer risk (including total, obesity-related and breast cancers), among women aged 30 years old or older in the FOS study.