A Mediterranean diet is high in vegetables, fruits, whole grains, and olive oil and low in meat, sweets, and saturated fat. It is linked to lower risks of cancer and relief of some symptoms and imbalances common among people with cancer.
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This section does not replicate the other information on this topic but provides additional details or context most relevant to professionals.
Clinical practice guidelines for professionals
It is recommended that primary care clinicians should counsel survivors to achieve a dietary pattern that is high in vegetables, fruits, whole grains, and legumes; low in saturated fats; and limited in alcohol consumption.
The 2021 NCCN survivorship care guidelines recommend that health professionals take these actions with cancer survivors, consistent with a Mediterranean diet:
- Assess dietary pattern for daily intake of fruits, vegetables, and unrefined grains, as well as red and processed meats, alcohol, and processed foods or beverages with added fats and/or sugars.
- All survivors should be encouraged to eat a diet that is at least 50% plant-based, with the majority of food being vegetables, fruit, and whole grains.
Recommended sources of dietary components:
- Fat: plant sources such as olive or canola oil, avocados, seeds and nuts, and fatty fish
- Carbohydrates: fruits, vegetables, whole grains, and legumes
- Protein: poultry, fish, legumes, low-fat dairy foods, and nuts
Modes of action: epigenetic changes
An epigenetic mechanism may explain how a Mediterranean diet leads to a decrease in inflammatory markers. Greater changes were found in the methylation of genes associated with inflammation and lower concentration of CRP and TNF-α among people with type 2 diabetes or cardiovascular risk factors who were given a Mediterranean diet intervention compared to a low-fat diet.1Arpón A, Riezu-Boj JI et al. Adherence to Mediterranean diet is associated with methylation changes in inflammation-related genes in peripheral blood cells. Journal of Physiology and Biochemistry. 2016 Aug;73(3):445-455.
Modes of action: microbiome/metabolome changes
Diet can alter the microbiome, which in turn interacts with the immune system to affect health outcomes, possibly through modulation of the overall inflammatory state of the body terrain.
Strong evidence shows that switching from a diet with low fiber, low poly- and mono-unsaturated fatty acids, and greater saturated fatty acids to a Mediterranean diet leads to alterations in the gut microbiota. These changes are less associated with dysbiosis (dominance of taxa associated with disease) and more aligned with eubiosisdominance of microbial taxa associated with lower risk of disease. The mechanisms and interactions of the human microbiome with mental and physical health are immensely complex but largely involve metabolism of dietary components by the microbiota to produce metabolites which in turn interact with the immune and nervous systems to alter the body terrain in an ongoing dance of homeostasis. The Mediterranean diet is mentioned specifically in the context of encouraging a eubiotic state for the human gut microbiome.2García-Montero C, Fraile-Martínez O et al. Nutritional components in western diet versus Mediterranean diet at the gut microbiota-immune system interplay. implications for health and disease. Nutrients. 2021;13(2):699.
Most studies on the Mediterranean diet and its modulation of the microbiome have involved participants with generally healthy functioning immune systems. The interaction of diet, microbiome, and a pathologic immune system are discussed among HIV+ people.3Pastor-Ibáñez R, Blanco-Heredia J et al. Adherence to a supplemented Mediterranean diet drives changes in the gut microbiota of HIV-1-infected individuals. Nutrients. 2021;13(4):1141.
No difference was detected in the variation of gut microbiota within a Mediterranean-diet group or between the Mediterranean-diet group and control-diet group after a year-long intervention of a Mediterranean diet in a randomized controlled trial. However, researchers then shifted to a cross-sectional study of the participants, which revealed several significant associations between specific factors including, diet, nutrients, and BMI, but not age or cognition and the relative abundance of specific taxa with pro- or anti-inflammatory profiles.4van Soest APM, Hermes GDA et al. Associations between pro- and anti-inflammatory gastro-intestinal microbiota, diet, and cognitive functioning in Dutch healthy older adults: the NU-AGE study. Nutrients. 2020 Nov 12;12(11):3471.
The Mediterranean diet’s effects on colorectal cancer risk are summarized in a narrative.5Donovan MG, Selmin OI, Doetschman TC, Romagnolo DF. Mediterranean diet: prevention of colorectal cancer. Frontiers in Nutrition. 2017 Dec 5;4:59.
The endocannabinoid system may play a role in the connection between the Mediterranean diet, microbiome changes, and better metabolic regulation.6Tagliamonte S, Laiola M et al. Mediterranean diet consumption affects the endocannabinoid system in overweight and obese subjects: possible links with gut microbiome, insulin resistance and inflammation. European Journal of Nutrition. 2021;60(7):3703-3716.
Further evidence: preclinical evidence
- Shifting from a Mediterranean diet to a standard Western diet high in heavily processed foods and meats can negatively alter the microbiota in 1 day, and a diet high in sugar decreases necessary microbial diversity within 1 week in animal studies7Turnbaugh PJ, Ridaura VK et al. The effect of diet on the human gut microbiome: a metagenomic analysis in humanized gnotobiotic mice. Science Translational Medicine. 2009 Nov 11; 1(6):6ra14; Sen T, Cawthon CR et al. Diet-driven microbiota dysbiosis is associated with vagal remodeling and obesity. Physiology and Behavior. 2017 May 1;173:305-317.
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