Reflections on definitions and health benefits of the Mediterranean diet
Figure 8. Dariush Mozaffarian is Dean of the Friedman School of Nutrition Science & Policy at Tufts University. His research focuses on the effects of lifestyle, particularly diet, on cardiometabolic health and disease, on the global impacts of suboptimal nutrition on chronic diseases, and on the effectiveness of policies to improve diet and reduce disease risk. Image credit: Kent Dayton.
An impressive and ever-expanding body of evidence has taught us that overall dietary quality strongly influences health, in particular risk of cardiometabolic diseases such as coronary heart disease, diabetes, and obesity [ 119]. Indeed, suboptimal diet quality is now the leading modifiable cause of death and disability in the world [ 120]. In contrast to the erroneous notions that diet quantity - how much a person eats - or isolated single nutrients are most important, the most relevant characteristics of healthful diets are the overall patterns of foods consumed.
Among various dietary patterns, consistent and compelling evidence indicates that traditional Mediterranean-style diets produce substantial health benefits. Diverse cultures and agricultural patterns exist in the Mediterranean region: there is no one, pure 'Mediterranean diet'. Still, as discussed in the previous sections, traditional Mediterranean diets share fundamental characteristics, which either individually or together have been proven to improve cardiometabolic health. Because of this abundance of beneficial foods, such diets are also naturally lower in harmful foods such as highly processed snacks, cereals, and similar ready-made products; red and processed meats; and other refined grains, starches, and sugars [ 121].
Ecologic comparisons, prospective cohort studies, and randomized trials consistently demonstrate significant beneficial effects of Mediterranean-type diets and their components on cardiometabolic risk factors and disease endpoints [ 15, 119, 121- 123]. The Spanish PREDIMED trial demonstrated a reduction in the risk of cardiovascular events by approximately 30% when participants were advised to follow a Mediterranean diet, supplemented with either nuts or extra-virgin olive oil [ 15]. Notably, extra-virgin olive oil largely replaced regular (non-virgin) olive oil, suggesting that the benefits of olive oil may be more closely related to bioactive compounds in extra-virgin oils [ 124] rather than to monounsaturated fats per se. Mediterranean diets also improve glycemic control [ 125] and reduce the incidence of type 2 diabetes [ 31]. The key components of Mediterranean diets are also beneficial for weight loss in obese patients [ 126] and for preventing long-term weight gain in non-obese populations [ 127]. Thus, rather than focusing on reductions in total calories or portion sizes, or on increasing or decreasing isolated nutrients, an emphasis on overall diet quality according to types of foods consumed has the strongest evidence-base for reducing adiposity and preventing diabetes and cardiovascular diseases. The main exceptions to this food-focused approach may be dietary additives such as sodium and trans fat, because very similar foods can be consumed that are either higher or lower in these additives, indicating a separate need to target these nutrients.
How does the Mediterranean diet compare to other healthful diet patterns? One close relative is the Dietary Approaches to Stop Hypertension (DASH) diet, which shares many of the same characteristics. Notably, while the original DASH diet was lower in fat and higher in carbohydrate, controlled clinical trials demonstrate that a higher-fat DASH diet, rich in healthful vegetable oils and nuts, produces even larger cardiometabolic benefits than the original low-fat DASH diet [ 128, 129]. People are also increasingly asking about vegetarian or vegan diets to improve their health. Unfortunately, because such diets are defined only by what is not consumed, the concept provides little accurate guidance for health. For instance, French fries, soda, and ketchup are vegetarian, as are refined grains, sugars, starches, sodium, and industrial trans fat. It is true that people who choose to be vegetarians or vegans are often health-conscious, so that they more often select healthier, minimally processed foods consistent with a Mediterranean diet [ 130]. However, a vegetarian or vegan diet per se - that is, the sole absence of animal products -has little influence on health, as true healthful diets are best defined by what is consumed, while also being characterized by lower consumption of unhealthful foods, many of which are actually 'vegetarian'.
Unfortunately, diets in the Mediterranean region have worsened over time. In Crete, a Mediterranean island with historically low rates of chronic disease, the diets now contain less fruit and olive oil and more meats than diets of earlier generations, with associated population increases in serum cholesterol and adiposity [ 131]. A global dietary Renaissance is required, returning the traditional Mediterranean diet to its primacy in the region and, crucially, incorporating our knowledge of its numerous health benefits to practical, regionally tailored dietary guidance and policies worldwide.
Competing interests
Dr. Mozaffarian reports ad hoc honoraria from Bunge, Pollock Institute, and Quaker Oats; ad hoc consulting for Foodminds, Nutrition Impact, Amarin, Astra Zeneca, and Life Sciences Research Organization; membership, Unilever North America Scientific Advisory Board; and royalties for a chapter on fish oil from UpToDate.
Mediterranean diet: from tradition and empiric description to modern science
Figure 9. Michel de Lorgeril is a cardiologist and nutritionist at the French National Centre for Scientific Research and the School of Medicine at Grenoble University, France. In the 1990s he proposed a theory to explain the French paradox (low mortality rate from cardiac disease in France compared with UK and USA despite similar risk profiles), and his research group demonstrated that the plant omega-3 fatty acid (alpha-linolenic acid) is cardioprotective. Michel de Lorgeril was the principal investigator on the landmark Lyon Diet Heart Study, the first clinical trial to demonstrate the beneficial effects of the Mediterranean diet in the prevention of ischemic heart disease.
The term ' Mediterranean diet' usually describes the dietary habits of populations living near the Mediterranean Sea [ 27]. The definition of the Mediterranean diet varies with geography, historical time and the nationality of the authors. In reality, the traditional dietary habits of the Greeks in 1950 were neither those of the Italians at that time, nor those of the Spaniards or Lebanese in 2014, although all of them do live on the shores of the Mediterranean Sea. These differences mainly explain the controversy about the definition of the Mediterranean diet.
After years of biological and medical research [ 27], it is definitely possible to look at the Mediterranean diet as a robust and complex scientific concept. It can be used by any practitioner, provided it is adapted to each specific geographic area and population, and called the modernized Mediterranean diet [ 27]. The next paragraphs will try to explain the shift from the empiric description of the traditional dietary habits of various Mediterranean populations to modern scientific medicine.
One good example is the dietary fat issue. It cannot be summarized with a single statement about olive oil. Briefly, Mediterranean people use several types of fats, from both plant and animal (including marine) sources. Many different fatty acids make up these fats. As shown in Table 2, comparing the modernized Mediterranean diet with a Western-type diet - grossly defined as the dietary habits of the US and North European (Finland, the Netherlands) populations investigated in the Seven Countries Study [ 3] -, it is important to differentiate oleic acid (the main monounsaturated fatty acid) provided by olive oil and the same chemical provided by animal fat. Oleic acid is indeed one of the main fatty acids of beef and pork fat. When the relations between the intake of oleic acid and any health item are analyzed within a Western cohort, investigators mainly analyze the relations with beef and pork consumption. When they do the same within a Mediterranean cohort, they analyze the relations with olive oil and the results are totally different. This may explain why certain (Western) experts refuse to acknowledge any health benefit from consuming olive oil, as if olive oil and oleic acid are the same things.
Table 2. Dietary fats in the modernized Mediterranean diet compared with a Western-type diet
On the other hand, while the modernized Mediterranean diet is not a vegetarian diet, it is definitely a plant-based diet. It is, therefore, crucial to identify the main sources of the essential omega-3 and omega-6 polyunsaturated fatty acids. Since olive oil is poor in both omega-6 and omega-3 fatty acids, what are the true sources of omega-3 and omega-6 fatty acids in either the traditional or the modernized Mediterranean diet? Along the same line, it is crucial to differentiate the main sources of the specific omega-3 fatty acids - those provided by plants and those provided by marine or terrestrial animals - and also the main sources of omega-6 fatty acids from either plants or animals (Table 2).
Finally, in the contemporary world where industrial foods are consumed by more and more people, it would be a mistake to still think that most saturated fats come from animal foods. Actually, saturated fatty acids also come from plants, such as the palm oil and cocoa butter incorporated in industrial foods. In the same way, it is essential to differentiate the (toxic) trans fatty acids produced by the industrial hydrogenation process and the (healthy) trans fatty acids naturally produced by ruminants and found in the dairy products typical of the Mediterranean diet.
All of these fat items, as well as other dietary items, illustrate how the empirical description of the traditional Mediterranean diet has become a modern scientific concept [ 27]. This is important to understand in order to design the optimal nutrition strategy to prevent disease. For instance, when testing the effects of the Mediterranean diet against cardiovascular complications in a controlled trial among French patients whose dietary habits were very different from the traditional Mediterranean diet, we were able to reproduce the main dietary aspects of the Mediterranean diet as regards fat (Table 2), without exclusively using olive oil [ 16, 39]. By advising our patients to use canola oil and canola oil-based margarine, plus some other Mediterranean foods - including olive oil, fatty fish, and nuts - we did reproduce the blood fatty acid profile characteristic of Mediterranean populations, with the appropriate omega-3/omega-6 ratio [ 132]. This may, at least in part, explain the impressive protection observed in the Lyon Diet Heart Study [ 16, 39], which was recently confirmed in the PREDIMED trial [ 15].
Thus, future trials testing the effects of a modern version of the Mediterranean diet in various clinical contexts (prevention of cancer or Alzheimer-type dementia) or future epidemiological studies should include that new knowledge in their protocols and designs. As an example, it will be important to differentiate the different essential (both omega-3 and omega-6) polyunsaturated fatty acids and also their food sources, animal versus plant (Table 2).
Finally, it is noteworthy that wheat, both whole and refined, is a major ingredient of the Mediterranean diet, mainly under the form of bread, but also of other typical Mediterranean diet foods, such as pasta and couscous [ 27, 133]. The physicians and nutritionists who are aware of the basic principles of the modernized Mediterranean diet recommend eating complex carbohydrates and whole grains, in particular bread and other wheat-based foods. However, the last decades have seen great changes in the prevalence and clinical presentation of two diseases linked to wheat: the celiac gluten-induced enteropathy and non-celiac gluten sensitivity [ 134, 135]. These changes have taken place as new wheat hybrids were introduced into human foods [ 134]. This is definitely a critical medical and environmental issue, which needs to be appropriately managed by physicians when their patients report new gastrointestinal or non-gastrointestinal symptoms after adhering to the modernized Mediterranean diet. The worst thing to do would be to deny the reality of these symptoms. There are alternatives to gluten-rich grains, and physicians and nutritionists should be careful to select such alternatives so as to respect the basic principles of the modernized Mediterranean diet. Thus, the gluten/wheat issue illustrates how a dietary pattern is not a static thing, but rather an ongoing change
In summary, even if wheat bread and olive oil are the very symbols of the traditional Mediterranean diet, a modernized Mediterranean diet concept makes it possible to obtain all the health benefits of typically Mediterranean dietary habits without olive oil or wheat bread. In other words, the modernized Mediterranean diet concept opens the way to a scientifically-founded protective dietary pattern which could be independent from the Mediterranean geography, climate and cultures. Future research - for instance when constructing a modern Mediterranean diet score in observational epidemiologic study - will have to integrate that new knowledge [ 134, 135].
Competing interests
The author declares that he has no competing interests.
References (Omitted)
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BMC Medicine 2014, 12:112 doi:10.1186/1741-7015-12-112
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Entities 0 Name: Mediterranean Count: 41 1 Name: Lyon Count: 2 2 Name: France Count: 2 3 Name: Michel de Lorgeril Count: 2 4 Name: Mediterranean Sea Count: 2 5 Name: Creative Commons Attribution License Count: 1 6 Name: USA Count: 1 7 Name: French National Centre for Scientific Research Count: 1 8 Name: Friedman School of Nutrition Science & Policy Count: 1 9 Name: Dr. Mozaffarian Count: 1 10 Name: Pollock Institute Count: 1 11 Name: Grenoble University Count: 1 12 Name: Unilever North America Scientific Advisory Board Count: 1 13 Name: Kent Dayton Count: 1 14 Name: UpToDate Count: 1 15 Name: Quaker Oats Count: 1 16 Name: Life Sciences Research Organization Count: 1 17 Name: French Count: 1 18 Name: BioMed Central Ltd. Count: 1 19 Name: Astra Zeneca Count: 1 20 Name: Creative Commons Public Domain Dedication Count: 1 21 Name: Netherlands Count: 1 22 Name: Finland Count: 1 23 Name: Amarin Count: 1 24 Name: Tufts University Count: 1 25 Name: School of Medicine Count: 1 26 Name: Dean Count: 1 27 Name: Bunge Count: 1 28 Name: BMC Medicine Count: 1 29 Name: US Count: 1 30 Name: UK Count: 1 31 Name: Crete Count: 1 32 Name: Dariush Mozaffarian Count: 1 Related 0 Url: http://ift.tt/1nIXvPJ Title: What is the alkaline diet? Description: You hear about the alkaline diet a lot - from health coaches, celebrities, and even some doctors will offer information about alkaline foods. So what is an alkaline diet, and is there any evidence that it's helpful? The idea behind an alkaline diet is that you can help your body maintain a healthy blood pH through the food you eat.
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