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The Mediterranean Diet is Really Good For You – Fact or Fad?

A literature review on this increasingly popular diet

What exactly is the Mediterranean diet?

The Mediterranean diet (MD) is one of the better known and well-studied dietary patterns that has consistently been shown to have a beneficial influence on health and longevity.[1],[2],[3],[4] It is recognized by the World Health Organization as a healthy and sustainable dietary pattern and is a way of eating based on the countries that border the Mediterranean Sea. There is no unified consensus on precisely what the MD is, because diets vary between these countries and even within an individual country.  Differences in culture, ethnicity, religion, economy, and agricultural all play a role in variations on what is being consumed. However, there are some common features seen across all Mediterranean countries. Healthy fats are a mainstay of the MD, predominantly coming from olive oil, nuts, and fish (and other seafood); daily consumption of plant-derived foods such as fruits, vegetables, whole grains, and legumes; mild to moderate amounts of dairy, poultry, and eggs; and a minimal amount of red meat is eaten. Other important elements of the MD worth noting – mild to moderate wine consumption (mostly red) and being physically active.[3],[5],[6]

Healthy fats are a mainstay of the Mediterranean Diet, predominantly coming from olive oil, nuts, and fish; daily consumption of plant-derived foods and a minimal amount of red meat is eaten.

Interest in the MD began in the 1960s with the observation that there was a lower rate of cardiovascular disease in Mediterranean countries than in the United States and Europe. This observation, in addition to epidemiological and experimental studies suggesting that diets rich in whole grains, fruit and vegetables, and a lower intake of animal fat may have cardio-protective effects, led to a hypothesis that a Mediterranean dietary pattern was protective against cardiovascular disease (CVD).[7],[8],[9] Since that time, a very large number of studies have reported that a higher adherence to MD may decrease CVD incidence and mortality, including coronary heart disease (CHD) and myocardial infarction (MI).[10] In addition to its cardioprotective effects, there is growing evidence that a MD can favorably impact cognitive and metabolic disorders, inflammatory parameters, and cancer incidence.[11]

In addition to its cardioprotective effects, there is growing evidence that a Mediterranean Diet can favorably impact cognitive and metabolic disorders, inflammatory parameters, and cancer incidence.

 Given the extremely large amount of research looking at how the MD impacts health, this article will summarize the results of recent meta-analyses and systematic reviews. A systematic review attempts to answer a specific research question by collecting and summarizing all empirical evidence that fits specified eligibility criteria. A meta-analysis is the use of statistical methods to summarize the results of these studies. Umbrella reviews are overviews of existing systematic reviews and/or meta-analyses and are relatively new study designs that help provide a comprehensive and systematic examination of the scientific literature available for a specific research topic.[12]

 Can a Mediterranean diet impact your health?

In recent years, the MD has been linked to decreased risk of dementia and cognitive decline.[13],[14] In 2017, a systemic review examined the association between the MD and cognitive health.[15] In this review, most of the studies that examined the effectiveness of the MD on non-communicable diseases, primarily in an older adult population, showed significant health benefits from following this type of dietary pattern. A MD was related to lower risk of cardiovascular disease, metabolic syndrome, mortality, and better mental health – especially in those demonstrating better adherence to the diet. Overall, subjects with a higher MD adherence score had a better nutrient profile.[16],[17] Countries in Europe, near the Mediterranean Sea, had an even better nutrient intake, especially for B-vitamins, omega-3 fatty acids, zinc, vitamins B12 and D, selenium, and iodine – most of which may play a role in improving cognitive function and lowering the risk of AD.[18],[19],[20],[21],[22],[23],[24] Authors also note that the MD lowers the risk of cognitive decline by reducing the risk factors associated with CVD, with CVD itself being a known risk factor for dementia.[10] A meta-analysis of six trials showed that the MD favorably impacted body weight, serum cholesterol, and CRP; all of which are risk factors for CVD.[25] This supported an earlier, population-based cohort study, where it was determined that after 10 years of following the MD, participants with the highest MD adherence scores had a lower risk of developing myocardial infarction (26%) and stroke (22%).[26] A meta-analysis of 11 studies in 2017 reached a similar conclusion in that participants with the highest MD adherence score had a significantly lower risk of developing CVD and CHD.[10]

Increased adherence to this diet improves health outcomes

In an umbrella review across 13 meta-analyses of observational studies and 16 meta-analyses of randomized clinical trials (RCTs) involving a total population of more than 12,800,000 subjects, the association between the adherence to the MD and 37 health outcomes was investigated.[11] It was demonstrated that a two-point increase in adherence score resulted in a significant reduction of overall mortality, and a reduced risk of cardiovascular disease, cancer, and neurodegenerative diseases.[27],[28],[29] Furthermore, meta-analyses of RCTs demonstrated that subjects allocated to a MD, compared to those with a control diet, had lower anthropometrical (body fat composition and bodily circumference at the waist, hip, and chest), metabolic and inflammatory risk parameters. Accordingly, the authors determined there was suggestive evidence supporting the effectiveness of the MD in reducing weight, BMI and waist circumference, lowering total cholesterol, and increasing HDL cholesterol levels, when compared to control diets.[10],[11],[30],[31],[32],[33] Few of the meta-analyses in this review evaluated inflammatory parameters, but the majority confirmed an inverse relationship between a higher adherence score, CRP and interleukin (IL)-6 (inflammatory markers).[30],[34],[35] As for metabolic disorders, an association between the MD and reduced risk of diabetes was the most robust, whereas evidence for a protective effect against metabolic syndrome, though present, was weaker. The analysis of RCTs, however, did provide suggestive evidence for better glycemic control and reduced insulin resistance in subjects following the MD diet vs. those following a control diet.[32],[33],[36],[37],[38]

In the conclusion of this very large umbrella review (encompassing more than 12 million individuals), authors summarized that there is a significant amount of evidence suggesting that a greater adherence to the MD reduces the risk of overall mortality, cardiovascular disease, coronary heart disease, myocardial infarction, overall cancer incidence, neurodegenerative disease and diabetes.

In a large review, encompassing more than 12 million individuals, authors summarized that there is a significant amount of evidence suggesting a greater adherence to the Mediterranean Diet reduces the risk of overall mortality, cardiovascular disease, coronary heart disease, myocardial infarction, overall cancer incidence, neurodegenerative disease, and diabetes.

Of all the dietary recommendations I have made over the years, the MD dietary pattern, by far, has been the most frequently recommended. I believe one of the reasons this diet has experienced such a high level of success, favorably impacting many different health conditions, is that it is simple and straight forward. For starters, by simply minimizing basic things like sugar, processed foods, fried foods, and excessive amounts of meat, you are already headed in the right direction. Secondly, its emphasis on consuming a variety of healthy and nutritional foods such as fruits, vegetables, beans/legumes, fish/seafood, and healthy fats from olive oil, avocados, and nuts/seeds significantly enhances its appeal. And finally, especially for wine lovers, adding a glass of red wine to your dinner is “icing on the cake”.  With reasonable dietary restrictions and easy access to a wide variety of tasty foods, this dietary approach is very amenable to most, therefore dramatically increasing compliance and adherence.  The results are priceless:  a reduced risk for several chronic diseases and an overall healthier, happier lifestyle. This doctor strongly believes the Mediterranean diet is here to stay!

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