History of Medicine
Something New under the Sun? The Mediterranean Diet and Cardiovascular Health
Sarah W. Tracy, Ph.D.
N Engl J Med 2013; 368:1274-1276
In this issue of the Journal, Estruch et al. (pages 1279–1290) report the positive results of PREDIMED (Prevención con Dieta Mediterránea), a randomized trial of the Mediterranean diet (supplemented 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 Japanese and traditional vegetarian diets. Yet in many ways, that is old news. The history of dietary guidelines for heart health — a project begun in the 1950s when the United States felt threatened by a perceived “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 fish. Meals were said to be “swimming” in olive oil and prepared simply in ways that “preserved the nutritive value of the food rather well.”2
The first epidemiologic data supporting the Mediterranean diet came from the Seven Countries Study (SCS), a prospective investigation of diet and other cardiovascular-disease risk factors in 16 cohorts totaling nearly 13,000 men in the United States, Italy, Greece, Yugoslavia, Finland, the Netherlands, and Japan, which began in 1958. The PREDIMED results would come as little surprise to the man behind the SCS, American physiologist and epidemiologist Ancel Keys, who advanced the low-fat diet and the low-saturated-fat Mediterranean diet for the primary 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 cardiovascular 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 cholesterol levels and cardiovascular disease risk.
The still-unfolding story of dietary fat has proven more complicated than Keys envisioned, but his observations about dietary patterns in various cultures — Mediterranean, northern European, and Asian — appear prescient today. The nutritional properties of whole foods and food patterns — rather than macronutrients (such as protein, 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 Sometimes 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 specific vitamins, and the prevention of deficiency diseases such as beriberi, pellagra, and scurvy. By midcentury, chronic diseases such as atherosclerosis, hypertension, and cancer were recognized as the dominant health threats in the developed world. Yet the reductionism that guided the early studies continued to influence explorations of diet and heart disease. In the 1950s and 1960s, biochemists, clinical scientists, and epidemiologists focused on macronutrients as potential contributors to cardiovascular disease and debated what constituted proof of a causal link between dietary fat and heart disease. 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 dietary guidelines for the prevention of cardiovascular disease in 1957. The guidelines were brief and tentatively worded, reflecting controversy over the hypothesized link between dietary fat and heart disease. 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, specifically fats. Committed to reducing 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 catering to heart health first appeared in the 1950s, offering recipes for limiting caloric intake and reducing dietary fat and cholesterol. The first cookbook to promote the hypothesized relationship between 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 cookbook, Dietary Prevention and Treatment 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 irreducible elements of a healthy diet, something he and others struggled to do in the laboratory. As food-policy expert Marion Nestle has observed, there is striking similarity between Keys's 1959 recommendations and those in recent editions of the Dietary Guidelines for Americans from the U.S. Department of Agriculture (USDA) and the Department of Health and Human Services.4
Since 1980, these guidelines, revised every 5 years, have set dietary standards for an increasingly obese and diabetic American public. In part, they reflect an ongoing dance between evidence-based dietary 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 vegetable oils; and substitute whole grains for refined ones. This advice should sound familiar, yet because the 2010 guidelines often use difficult-to-translate macronutrient language and fill more than 95 pages, they have become less accessible to the public. And the USDA nutritional icon “MyPyramid” (2005) and its replacement, “MyPlate” (2011), intended to distill 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, Scientific, and Cultural Organization (UNESCO) placed the Mediterranean diet on its Intangible Cultural Heritage 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.
From McClendon Honors College, University of Oklahoma, Norman.