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An updated systematic review and meta-analysis on adherence to mediterranean diet and risk of cancer.
Morze, J, Danielewicz, A, Przybyłowicz, K, Zeng, H, Hoffmann, G, Schwingshackl, L
European journal of nutrition. 2021;60(3):1561-1586
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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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The Effects of Extra Virgin Olive Oil on Alanine Aminotransferase, Aspartate Aminotransferase, and Ultrasonographic Indices of Hepatic Steatosis in Nonalcoholic Fatty Liver Disease Patients Undergoing Low Calorie Diet.
Shidfar, F, Bahrololumi, SS, Doaei, S, Mohammadzadeh, A, Gholamalizadeh, M, Mohammadimanesh, A
Canadian journal of gastroenterology & hepatology. 2018;2018:1053710
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Non-alcoholic fatty liver disease (NAFLD) is a risk factor for cardiovascular disease (CVD), which is the most common cause of death. The traditional Mediterranean diet has been shown to reduce the risk of NAFLD and CVD and this protective effect is thought to be in part due to the use of olive oil in this dietary pattern. The aim of this randomised, single-blind study was to evaluate the effect of virgin olive oil as part of a low-calorie diet on markers of NAFLD. 43 overweight or obese patients with NAFLD, characterised by increased liver enzymes (ALT and AST), were randomised to either a low calorie diet with normal fat or a low calorie diet with 20% of total energy intake from olive oil (overall percentage of fat 30% of total energy intake in both groups) for three months. Significant weight loss was observed in both groups, with no significant difference between groups. There was a reduction in liver enzymes in the olive oil group which was significantly greater than in the control group. The severity of liver steatosis (the accumulation of fat in the liver) did not change significantly in either group. The authors concluded that a low calorie diet with virgin olive oil led to slight weight loss and improvements in markers for NAFLD.
Abstract
Background: Coronary artery disease is the most common cause of death in the patients with nonalcoholic fatty liver disease (NAFLD). Studies have shown that there is a strong relation between the increase in the aminotransferase levels and fat accumulation in the liver with cardiovascular complications, independent of all aspects of the metabolic syndrome. This study aimed to examine the effect of virgin olive oil on alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and the severity of steatosis in the NAFLD patients undergoing a weight-loss diet. Methods: This clinical trial was carried out on 50 patients with nonalcoholic fatty liver (mean age of 45.91 ± 9.61 years, mean BMI of 29.7 ± 0.58 Kg/m2) and the subjects were randomly assigned to the olive oil group (receiving the equivalent of 20% of their total daily energy requirement from olive oil) or the control group (with normal consumption of oil) for 12 weeks. All the patients received a hypocaloric diet during the study. At the beginning and the end of the study, the serum levels of ALT and AST and liver steatosis were measured. Findings: A significant decrease in the level of ALT enzymes was observed in the control group at the end of the study (P = 0.004). In the olive oil group, both enzymes decreased compared to baseline measurements (P < 0.01). There were significant differences in the ALT and AST levels between the two groups (P < 0.02). The severity of liver steatosis did not change significantly during the study. Conclusion: The consumption of a low calorie diet enriched with olive oil, along with slight weight reduction, reinforces the desired effects of weight loss in improving the levels of the hepatic enzymes.
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Impact of Consuming Extra-Virgin Olive Oil or Nuts within a Mediterranean Diet on DNA Methylation in Peripheral White Blood Cells within the PREDIMED-Navarra Randomized Controlled Trial: A Role for Dietary Lipids.
Arpón, A, Milagro, FI, Razquin, C, Corella, D, Estruch, R, Fitó, M, Marti, A, Martínez-González, MA, Ros, E, Salas-Salvadó, J, et al
Nutrients. 2017;10(1)
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Our genes are not fixed. They interact constantly with the environment through dietary and lifestyle factors, which affect whether genes are expressed or not. This is often referred to as epigenetic modulation. DNA methylation is an epigenetic mechanism that adds a methyl group to DNA, thereby modifying the function of the genes and affecting gene expression. Epigenetic alterations have been associated with conditions, such as obesity, type 2 diabetes, cardiovascular disease and immunological conditions. It is suggested that epigenetic marks are reversible and can be modulated by nutrient status and certain dietary components. The aim of the current study was to explore methylation changes in genes of peripheral white blood cells in a subset of participants from the PREDIMED-Navarra randomised controlled trial. 36 participants were allocated to three groups, all consuming a Mediterranean diet. In the first group, the diet was supplemented with extra virgin olive oil (EVOO), in the second group, with mixed nuts, and the third group, which served as the control group, were advised to consume a low-fat diet. Changes in DNA methylation were analysed from blood samples at baseline and at five-year follow-up. The authors observed methylation changes in several genes, related to metabolism, glucose and energy regulation, diabetes and inflammation, after the consumption of EVOO and nuts. They concluded that the beneficial effects of Mediterranean diets that include EVOO and nuts, may, at least in part, be mediated via epigenetic mechanisms. As these foods are high in monounsaturated and polyunsaturated fats, the quality of fat may be playing an important role in this mediation.
Abstract
DNA methylation could be reversible and mouldable by environmental factors, such as dietary exposures. The objective was to analyse whether an intervention with two Mediterranean diets, one rich in extra-virgin olive oil (MedDiet + EVOO) and the other one in nuts (MedDiet + nuts), was influencing the methylation status of peripheral white blood cells (PWBCs) genes. A subset of 36 representative individuals were selected within the PREvención con DIeta MEDiterránea (PREDIMED-Navarra) trial, with three intervention groups in high cardiovascular risk volunteers: MedDiet + EVOO, MedDiet + nuts, and a low-fat control group. Methylation was assessed at baseline and at five-year follow-up. Ingenuity pathway analysis showed routes with differentially methylated CpG sites (CpGs) related to intermediate metabolism, diabetes, inflammation, and signal transduction. Two CpGs were specifically selected: cg01081346-CPT1B/CHKB-CPT1B and cg17071192-GNAS/GNASAS, being associated with intermediate metabolism. Furthermore, cg01081346 was associated with PUFAs intake, showing a role for specific fatty acids on epigenetic modulation. Specific components of MedDiet, particularly nuts and EVOO, were able to induce methylation changes in several PWBCs genes. These changes may have potential benefits in health; especially those changes in genes related to intermediate metabolism, diabetes, inflammation and signal transduction, which may contribute to explain the role of MedDiet and fat quality on health outcomes.