Предимствата на средиземноморската кухня – III част

Something New under the Sun? The Mediterranean Diet and Cardiovascular Health

Sarah W. Tracy, Ph.D.

 

n engl j med 368;14 nejm.1274 org april 4, 2013

 

In this issue of the Journal, Es- truch et al. (pages 1279–1290) report the positive results of PREDIMED (Prevención con Dieta Mediterránea), a randomized trial of the Mediterranean diet (supple- mented  with  either  extra-virgin olive oil or nuts) for the primary prevention of cardiovascular events. The data are impressive and seem to support the high ranking of the  Mediterranean diet and its constituent foods among various cardioprotective vegetable- and fruit-rich regimens, such as DASH (Dietary Approaches to Stop Hypertension) and Japa- nese and traditional vegetarian diets. Yet in many ways, that is old news. The history of dietary guide- lines for heart health — a project begun in the 1950s when the Unit- ed States felt threatened by a per- ceived “epidemic” of heart attacks — reveals that the Mediterranean diet’s cardiovascular benefits have been recognized for decades. As early as 1948, the Rockefeller Foundation assessed the health, economic, and social status of Cretan Greeks and noted that their “impoverished” diet was rich in cereal grains, legumes, wild greens and herbs, and fruits, paired with limited  meat, milk, and f ish. Meals were said to be “swimming” in olive oil and prepared simply in ways that “preserved the nutritive value of the food rather well.”2Increasingly, the Mediterranean diet  has  become  the  standard for healthy eating. Adherence to it appears to reduce the risk of car- diovascular  disease, cancer, Alz- heimer’s  disease, and Parkinson’s disease, as well as the risk of death due to cardiovascular  disease or cancer and even premature  death overall.1 Largely plant-centered, with high intakes of olive oil, fruit, nuts,   and  whole-grain  cereals, moderate consumption of fish and poultry, low intakes of dairy, red meat, and sweets, and often mod- erate drinking  of red wine, the “classic”  Mediterranean diet  is younger  than  the region’s  history suggests.  In fact, this dietary pat- tern was first observed in Greece, Italy, and Spain in the decade after World War II — an artifact  of postwar impoverishment that proved beneficial to health. Unfor- tunately, it is currently under siege in southern  Europe from the glo- balization of fast foods rich in re- f ined carbohydrates, sweets, and red meat.

The  f irst  epidemiologic  data supporting  the Mediterranean diet came from the Seven Countries Study (SCS), a prospective investigation of diet and other cardiovas- cular-disease risk factors in 16 co- horts  totaling  nearly 13,000 men in the United States, Italy, Greece, Yugoslavia, Finland, the Nether- lands, and Japan, which  began in 1958. The PREDIMED results would come as little surprise to the man behind the SCS, Ameri- can physiologist and epidemiologist Ancel Keys, who advanced the low-fat diet and the low-saturated- fat Mediterranean diet for the pri- mary and secondary prevention of heart  disease. Keys “discovered” the Mediterranean diet’s health benefits in the early 1950s, when visiting the region as a medical scientist concerned about the widely reported increase in heart attacks in the United States. After spending several years exploring the dietary patterns and cardiovas- cular status of men in Italy, Spain, and Crete, Keys launched the SCS. Study data (which are still being collected from elderly “survivors”) offered strong population-level support for the effects of dietary fat and fatty acids on serum cho- lesterol levels and cardiovascular disease risk.

The still-unfolding story of die- tary fat has proven more compli- cated than Keys envisioned, but his observations about dietary pat- terns in various cultures — Medi- terranean, northern European, and Asian — appear prescient today. The nutritional properties of whole foods and food patterns — rather than macronutrients (such as pro- tein, carbohydrate, and fat) and micronutrients (such as vitamins and minerals) — are an important focus  of  recent  research.  Many who study diet’s effects on disease note that we do not eat isolated nutrients. Instead, we form food patterns, consuming diets rich in fruits, nuts, vegetables, and oils or, alternatively, in highly processed foods, and these constituent foods interact synergistically.3 Some- times these synergies confer long- term benefits.

This holistic turn in nutrition science represents  something  of a paradigm shift. Early in the 20th century, research focused on the roles of micronutrients,  often spe- cific vitamins, and the prevention of deficiency diseases such as beri- beri, pellagra, and scurvy.  By mid- century, chronic diseases such as atherosclerosis, hypertension, and cancer were recognized as the dominant health threats in the de- veloped world. Yet the reduction- ism that guided the early studies continued  to  inf luence explora- tions of diet and heart disease. In the 1950s and 1960s, biochemists, clinical scientists, and epidemiolo- gists focused on macronutrients as potential contributors to cardiovas- cular disease and debated what constituted  proof of a causal link between dietary fat and heart dis- ease. Individual macronutrients and bioactive compounds  in food, such as cholesterol, were the focus of research exploring diet’s relation to the health status of populations.

In this context, the American Heart Association (AHA) Ad Hoc Committee on Dietary Fat and Atherosclerosis issued the first di- etary guidelines for the prevention of cardiovascular disease in 1957. The guidelines were brief and ten- tatively worded, reflecting contro- versy over the hypothesized link between dietary fat and heart dis- ease. Obese people or those with a personal or family history of heart disease were urged to control their weight, reduce dietary fat to 25 to 35% of total energy intake, and substitute polyunsaturated fats for animal fats. The guidelines thus focused on macronutrients, spe- cifically fats. Committed to reduc- ing heart disease, the AHA revised its guidelines throughout the 1960s. By 1968, people of all ages were urged to limit dietary cholesterol as well and to adhere to principles of good nutrition.

When the AHA issued its first “heart healthy” cookbook, in 1973, it was a latecomer. Cookbooks ca- tering to heart health first ap- peared in the 1950s, offering reci- pes for limiting caloric intake and reducing dietary fat and cholester- ol. The first cookbook to promote the hypothesized relationship  be- tween diet and heart health was probably that of physician Helen Gofman, The Low Fat Low Cholesterol Diet (1951). Gofman’s husband, the medical physicist and lipidologist John Gofman, also wrote a cook- book,  Dietary Prevention and Treat- ment of Heart Disease (1958), examining the relationship of dietary carbohydrates to dietary fat in atherogenesis. There were many others, but the most popular were two cookbooks by Keys and his biochemist wife, Margaret, Eat Well and Stay Well (1959) and How to Eat Well and Stay Well the Mediterranean Way (1975). These interpreted “diet” in the classic Greek sense, as a “way of life,” and advocated moderate exercise in addition to “heart-healthy eating” that was grounded largely in Italian and Greek cuisine. Cookbooks, with their focus on dietary  pattern, allowed Keys to explore the irreduc- ible elements of a healthy diet, something he and others strug- gled to do in the laboratory. As food-policy expert Marion Nestle has observed, there is striking similarity between Keys’s 1959 rec- ommendations and those in recent editions of the Dietary Guidelines for Americans from the U.S. Depart- ment  of  Agriculture (USDA) and the Department of Health and Hu- man Services.4

Since 1980, these guidelines, revised every 5 years, have set die- tary standards for an increasingly obese and diabetic American pub- lic. In part, they reflect an ongoing dance between evidence-based die- tary advice and the food-industry lobby. In part, they reflect a stable dietary foundation for avoiding degenerative diseases: eat more fruits, vegetables, and nuts; limit red  meat  and  dairy;  consume more fish and poultry; curtail salt and sugar; use olive and other veg- etable oils; and substitute whole grains for refined ones. This ad- vice should sound familiar, yet be- cause the 2010 guidelines often use difficult-to-translate macronu- trient language and fill more than

95 pages, they have become less accessible to the public. And the USDA nutritional  icon  “MyPyra- mid” (2005) and its replacement, “MyPlate” (2011), intended to dis- till cumbersome dietary advice, have been criticized for being too simple, misleading, or excessively influenced by the food industry.5

In 2010, the United Nations Educational, Scientif ic, and Cul- tural Organization (UNESCO) placed  the  Mediterranean  diet on its Intangible Cultural Heri- tage list, a sort of endangered- species list of treasured  elements of cultures, valuable both in their native lands and globally. The PREDIMED results reinforce the Mediterranean   diet’s   value   for health internationally,  suggesting a dietary template that may be of particular value as chronic disease becomes a global issue.

 

Disclosure forms provided by the author are available with the full text of this arti- cle at NEJM.org.

 

1. Sofi F, Abbate R, Gensini GF, Casini A. Accruing evidence on benefits of adherence to the Mediterranean diet on health: an up- dated systematic review and meta-analysis. Am J Clin Nutr 2010;92:1189-96.

2. Allbaugh LG. Crete — a case study of an underdeveloped area. Princeton, NJ: Princeton University Press, 1953.

3. Jacobs DR Jr, Tapsell LC. Food, not nutrients, is the fundamental unit in nutrition. Nutr Rev 2007;65:439-50.

4. Nestle M. Mediterranean diets — historical and research overview. Am J  Clin Nutr 1995;61:Suppl:1313S-1320S.

5. Datz T. Harvard serves up its own ‘plate’: Healthy Eating Plate shows shortcomings in government’s MyPlate.  Harvard Gazette. September  24, 2011 (http://news.harvard.edu/gazette/story/2011/09/harvard-serves-up-its-own-plate/).

 

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