Increasingly,
the Mediterranean diet has become the standard for healthy eating.
Adherence to it appears to reduce the risk of cardiovascular disease,
cancer, Alzheimer'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 moderate drinking of
red wine, the “classic” Mediterranean diet is younger than the region's
history suggests. In fact, this dietary pattern 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.
Unfortunately, it is currently under siege in southern Europe from the
globalization of fast foods rich in refined carbohydrates, sweets, and
red meat.
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.1
Sofi F,
Abbate R,
Gensini GF,
Casini A.
Accruing evidence on benefits of adherence to the Mediterranean diet on
health: an updated systematic review and meta-analysis.
Am J Clin Nutr 2010;92:1189-1196
1
Sofi F,
Abbate R,
Gensini GF,
Casini A.
Accruing evidence on benefits of adherence to the Mediterranean diet on
health: an updated systematic review and meta-analysis.
Am J Clin Nutr 2010;92:1189-1196
CrossRef |
Medline
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;65:439-450
CrossRef |
Medline
4
Nestle M. Mediterranean diets -- historical and research overview.
Am J Clin Nutr 1995;61:Suppl:1313S-1320S
Web of Science |
Medline
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/).
No hay comentarios:
Publicar un comentario