Plain language summary
The development of cancer is associated with a number of risk factors, including smoking, obesity, sedentary lifestyles, alcohol consumption, infections, pollution, and dietary imbalances. Based on previous research, optimal consumption of fruits, vegetables, and whole grains, along with reduced consumption of red and processed meat, reduces cancer risk. According to this systematic review and meta-analysis, adherence to the Mediterranean diet is associated with lower cancer mortality and site-specific cancer development. A Mediterranean diet includes fruits, vegetables, nuts, legumes, fish, whole grains, extra virgin olive oil, and low amounts of red meat, processed meat, egg, and dairy, along with moderate amounts of red wine. According to this systematic review and meta-analysis, adherence to the Mediterranean diet reduces the risk of cancer mortality and the risk of developing cancers specific to the site, such as colorectal cancer, bladder cancer, gastric cancer, and lung cancer. Among the components of the Mediterranean diet, fruits, vegetables, and whole grains have been shown to reduce cancer risk. Bioactive substances found in Mediterranean diet components require additional robust studies to evaluate their benefits. A healthcare professional can use the results of this study to make clinical decisions and recommend therapeutic interventions to cancer patients.
Abstract
PURPOSE The aim of current systematic review was to update the body of evidence on associations between adherence to the Mediterranean diet (MedDiet) and risk of cancer mortality, site-specific cancer in the general population; all-cause, and cancer mortality as well as cancer reoccurrence among cancer survivors. METHODS A literature search for randomized controlled trials (RCTs), case-control and cohort studies published up to April 2020 was performed using PubMed and Scopus. Study-specific risk estimates for the highest versus lowest adherence to the MedDiet category were pooled using random-effects meta-analyses. Certainty of evidence from cohort studies and RCTs was evaluated using the NutriGrade scoring system. RESULTS The updated search revealed 44 studies not identified in the previous review. Altogether, 117 studies including 3,202,496 participants were enclosed for meta-analysis. The highest adherence to MedDiet was inversely associated with cancer mortality (RRcohort: 0.87, 95% CI 0.82, 0.92; N = 18 studies), all-cause mortality among cancer survivors (RRcohort: 0.75, 95% CI 0.66, 0.86; N = 8), breast (RRobservational: 0.94, 95% CI 0.90, 0.97; N = 23), colorectal (RRobservational: 0.83, 95% CI 0.76, 0.90; N = 17), head and neck (RRobservational: 0.56, 95% CI 0.44, 0.72; N = 9), respiratory (RRcohort: 0.84, 95% CI 0.76, 0.94; N = 5), gastric (RRobservational: 0.70, 95% CI 0.61, 0.80; N = 7), bladder (RRobservational: 0.87, 95% CI 0.76, 0.98; N = 4), and liver cancer (RRobservational: 0.64, 95% CI 0.54, 0.75; N = 4). Adhering to MedDiet did not modify risk of blood, esophageal, pancreatic and prostate cancer risk. CONCLUSION In conclusion, our results suggest that highest adherence to the MedDiet was related to lower risk of cancer mortality in the general population, and all-cause mortality among cancer survivors as well as colorectal, head and neck, respiratory, gastric, liver and bladder cancer risks. Moderate certainty of evidence from cohort studies suggest an inverse association for cancer mortality and colorectal cancer, but most of the comparisons were rated as low or very low certainty of evidence.
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