Abstract
The aim of the present systematic review and meta‐analysis of observational studies was to gain further insight into the effects of adherence to Mediterranean Diet (MD) on overall cancer mortality, incidence of different types of cancer, and cancer mortality risk in cancer survivors. Literature search was performed using the electronic databases PubMed, and EMBASE until 2 July 2015. We included either cohort (for specific tumors only incidence cases were used) or case–control studies. Study specific risk ratios, hazard ratios, and odds ratios (RR/HR/OR) were pooled using a random effect model. The updated review process showed 23 observational studies that were not included in the previous meta‐analysis (total number of studies evaluated: 56 observational studies). An overall population of 1,784,404 subjects was included in the present update. The highest adherence score to an MD was significantly associated with a lower risk of all‐cause cancer mortality (RR: 0.87, 95% CI 0.81–0.93, I 2 = 84%), colorectal cancer (RR: 0.83, 95% CI 0.76–0.89, I 2 = 56%), breast cancer (RR: 0.93, 95% CI 0.87–0.99, I 2=15%), gastric cancer (RR: 0.73, 95% CI 0.55–0.97, I 2 = 66%), prostate cancer (RR: 0.96, 95% CI 0.92–1.00, I 2 = 0%), liver cancer (RR: 0.58, 95% CI 0.46–0.73, I 2 = 0%), head and neck cancer (RR: 0.40, 95% CI 0.24–0.66, I 2 = 90%), pancreatic cancer (RR: 0.48, 95% CI 0.35–0.66), and respiratory cancer (RR: 0.10, 95% CI 0.01–0.70). No significant association could be observed for esophageal/ovarian/endometrial/and bladder cancer, respectively. Among cancer survivors, the association between the adherence to the highest MD category and risk of cancer mortality, and cancer recurrence was not statistically significant. The updated meta‐analyses confirm a prominent and consistent inverse association provided by adherence to an MD in relation to cancer mortality and risk of several cancer types.
Highlights
Dietary quality indexes (DASH pattern, and the Healthy Eating Index) are associated with reduced risk of chronic disease [1, 2]
The highest adherence score to an Mediterranean Diet (MD) was significantly associated with a lower risk of all-cause cancer mortality (RR: 0.87, 95% CI 0.81–0.93, I2 = 84%), colorectal cancer (RR: 0.83, 95% CI 0.76–0.89, I2 = 56%), breast cancer (RR: 0.93, 95% CI 0.87–0.99, I2=15%), gastric cancer (RR: 0.73, 95% CI 0.55–0.97, I2 = 66%), prostate cancer (RR: 0.96, 95% CI 0.92–1.00, I2 = 0%), liver cancer (RR: 0.58, 95% CI 0.46–0.73, I2 = 0%), head and neck cancer (RR: 0.40, 95% CI 0.24–0.66, I2 = 90%), pancreatic cancer (RR: 0.48, 95% CI 0.35–0.66), and respiratory cancer (RR: 0.10, 95% CI 0.01–0.70)
Two studies were included in the original version of this systematic review, data of these were extracted for the update in a modified form: the cohort by Kenfield et al [28] provided data on cancer survivors previously not synthesized, and the results by Cottet et al [33] on cancer recurrence were placed in a new context
Summary
Dietary quality indexes (DASH pattern, and the Healthy Eating Index) are associated with reduced risk of chronic disease [1, 2]. Cohort studies and case–control studies investigating the association between MD and risk of cancer mortality, cancer types; cancer mortality, and cancer recurrence among cancer survivors were included in this update (for differences between the original analysis and the revised version with respect to grouping of clinical outcomes, see “Statistical analysis”).
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