The Mediterranean Diet


Written by Charlotte Green


The Mediterranean Diet is a traditional dietary pattern followed by populations surrounding the Mediterranean Sea, particularly regions of Greece, Italy, and Spain. Many observational studies have linked adherence to the Mediterranean Diet with increased longevity and lower incidences of chronic lifestyle-associated diseases such as cardiovascular disease and type 2 diabetes. In fact, two of the world’s Blue Zones, geographical areas known for a higher proportion of centenarians, Sardinia and Ikaria, Greece, follow the Mediterranean diet. Although the traditional diet is partially responsible for their longevity, the whole Mediterranean lifestyle is also an important contributor. In traditional Mediterranean cultures, there is emphasis on daily physical activity and social connection, which plays an integral role in successful ageing.1


Key Principles:


· Predominantly plant-based, with an abundance of fresh, seasonal fruits and vegetables that provide essential vitamins, minerals, and fibre

· A variety of wholegrains

· Moderate fish consumption, a source of essential omega-3 fatty acids

· Small amounts of lean meat and fermented dairy, such as yoghurt and cheese

· Moderate red wine consumption, particularly in a social context

· Daily extra-virgin olive oil, one of the key features of the Mediterranean Diet and a source of polyphenols and polyunsaturated fatty acids.2


The key to the success of the Mediterranean Diet is eating a variety of plant-based foods, rather than single nutrients in isolation. All the components of the Mediterranean Diet work synergistically to provide a variety of health benefits.3


Health Benefits:


High adherence to the Mediterranean Diet is associated with a reduced risk of cardiovascular disease. In the PREDIMED study, where participants were instructed to follow an energy-unrestricted Mediterranean Diet with supplements of daily extra-virgin olive oil or nuts, which was compared to a control low-fat diet. They were followed for 4-5 years where researchers found a lower risk of cardiovascular-related events such as heart attack in the Mediterranean diet group.4


Furthermore, the Mediterranean Diet is linked to improved brain health and reduced risk of neurodegenerative diseases, including Alzheimer’s Disease. In a 20-year study of over 16,000 middle-aged and elderly Spanish individuals, a higher adherence to the Mediterranean Diet was associated with a 20% reduced risk of dementia and could delay onset of the disease. There was also a dose-response effect, meaning the higher the Mediterranean Diet score in dietary questionnaires, the lower the risk of developing dementia.5 This could be due to increased hippocampal volume and, the area of the brain most affected in Alzheimer’s Disease, and associated improvements in memory, when following the Mediterranean diet.6

Following a Mediterranean-style diet can also improve mood and protect our mental health. In fact, the SMILES trial successfully showed that the Mediterranean diet could be used as part of a treatment plant for depression. In the trial, participants with clinical depression were either guided through a Mediterranean diet plan with a dietitian or given social support for 12 weeks, alongside their current medications. The results indicated that the diet was the more effective treatment strategy, with a greater reduction in depressive symptoms.7


How does the Mediterranean Diet confer these health benefits?


The Mediterranean diet is high in sources of omega-3 fatty acids, such as EPA from fish and ALA, particularly from walnuts and plant oils like flaxseed. Omega-3 fatty acid consumption has been linked to longevity because of their antioxidant and anti-inflammatory properties. This means they are protective against diseases such as cardiovascular disease and Alzheimer’s Disease, as oxidative damage and chronic inflammation are implicated in the development of these conditions.8


Additionally, the Mediterranean Diet is rich in polyphenols, a powerful family of plant chemicals renowned for their health benefits. Good sources of polyphenols include berries, black grapes, red wine, coffee and cocoa.9 In particular, extra-virgin olive oil is rich in phenolic compounds and its frequent consumption is a hallmark of the Mediterranean diet. Different plant-based foods contain different combinations of various polyphenols, meaning diversity is key to their health benefits.10 Polyphenols are one of the most potent antioxidants, therefore protecting against cellular damage. In particular, resveratrol, a polyphenol abundant in grapes and red wine, is linked to heart health as it is known to reduce blood pressure by relaxing blood vessels.11 Furthermore, polyphenols are anti-inflammatory, which is significant when considering depression. Inflammation is one of the key contributors to depression12, meaning a diet high in polyphenols could play a role in improving mood.


It is thought that one of the main mediators of the anti-inflammatory properties of the Mediterranean diet could be the gut microbiota, the community of trillions of micro-organisms residing in the gastro-intestinal tract. The abundance of fruits and vegetables provide plenty of fibre and sources of prebiotics. Prebiotics are a certain type of fibre found in foods such as leeks, artichokes, onions, and garlic, that can only be digested by the gut microbiota. Polyphenol-containing foods are also examples of prebiotics. They provide a source of energy for gut bacteria, allowing them to thrive, increasing the diversity of beneficial species such as Lactobacillus and Bifidobacterium. When prebiotics are digested by the gut microbiota, they produce beneficial metabolites, including short chain fatty acids (SCFAs). SCFAs have various health benefits around the body, including roles in anti-inflammatory pathways.13 Therefore, the gut microbiota could be partially responsible for the positive impact of the Mediterranean diet on health and longevity. In fact, it has been noted that adherence to the Mediterranean diet in the elderly helps to reduce frailty via positive alterations in the gut microbiota and increased SCFA production.14


Key Takeaways:


· The Mediterranean diet is associated with increased longevity and lower incidence of age-associated diseases, such as cardiovascular disease and Alzheimer’s Disease

· When adopting a Mediterranean-style diet, the key is diversity. An abundance of different plant-based foods, containing a variety of beneficial vitamins, minerals, fibre and polyphenols, all work synergistically to confer health benefits

· The antioxidant and anti-inflammatory properties of Mediterranean diet components are perhaps most important for the benefits of this dietary pattern, and could be mediated in part by changes to the gut microbiota composition

· Longevity in the Mediterranean is not solely dependent on diet. Lifestyle factors such as regular physical activity and social connection are equally important for long term health and happiness.


References


1. Buettner, D. & Skemp, S. Blue Zones: Lessons From the World’s Longest Lived. American Journal of Lifestyle Medicine vol. 10 318–321 (2016).

2. Muñoz, M. A., Fíto, M., Marrugat, J., Covas, M. I. & Schröder, H. Adherence to the Mediterranean diet is associated with better mental and physical health. Br. J. Nutr. 101, 1821–1827 (2009).

3. Widmer, R. J., Flammer, A. J., Lerman, L. O. & Lerman, A. The Mediterranean diet, its components, and cardiovascular disease. Am. J. Med. 128, 229–238 (2015).

4. Estruch, R. et al. Primary Prevention of Cardiovascular Disease with a Mediterranean Diet Supplemented with Extra-Virgin Olive Oil or Nuts. N. Engl. J. Med. 378, e34 (2018).

5. Andreu-Reinón, M. E. et al. Mediterranean Diet and Risk of Dementia and Alzheimer’s Disease in the EPIC-Spain Dementia Cohort Study. Nutrients 13, 1–19 (2021).

6. Ballarini, T. et al. Mediterranean Diet, Alzheimer Disease Biomarkers and Brain Atrophy in Old Age. Neurology96, e2920–e2932 (2021).

7. Jacka, FN. et al. A randomised controlled trial of dietary improvement for adults with major depression (the ‘SMILES’ trial). BMC Med. 15, (2017).

8. Roman, GC., Jackson, RE., Gahdia, R., Roman, AN. & Reis, J. Mediterranean diet: The role of long-chain ω-3 fatty acids in fish; polyphenols in fruits, vegetables, cereals, coffee, tea, cacao and wine; probiotics and vitamins in prevention of stroke, age-related cognitive decline, and Alzheimer disease. Rev. Neurol. (Paris). 175, 724–741 (2019).

9. Cardona, F., Andrés-Lacueva, C., Tulipani, S., Tinahones, F. J. & Queipo-Ortuño, M. I. Benefits of polyphenols on gut microbiota and implications in human health. Journal of Nutritional Biochemistry vol. 24 1415–1422 (2013).

10. Pandey, K. B. & Rizvi, S. I. Plant polyphenols as dietary antioxidants in human health and disease. Oxid. Med. Cell. Longev. 2, 270–278 (2009).

11. Cheng, Y. C., Sheen, J. M., Hu, W. L. & Hung, Y. C. Polyphenols and Oxidative Stress in Atherosclerosis-Related Ischemic Heart Disease and Stroke. Oxid. Med. Cell. Longev. 2017, (2017).

12. Carvalho, K. M. B. et al. Does the Mediterranean Diet Protect against Stress-Induced Inflammatory Activation in European Adolescents? The HELENA Study. Nutrients 10, (2018).

13. Merra, G. et al. Influence of Mediterranean Diet on Human Gut Microbiota. Nutrients 13, 1–12 (2020).

14. Ghosh, T. S. et al. Mediterranean diet intervention alters the gut microbiome in older people reducing frailty and improving health status: the NU-AGE 1-year dietary intervention across five European countries. Gut 69, 1218–1228 (2020).




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