Mediterranean diet, traditional foods, and health: Evidence from the Greek EPIC cohort

Antonia Trichopoulou Abstract Background. For more than 50 years, the traditional Mediterranean diet has been considered healthpromoting, but it was not until the mid-1990s that the topic began to receive increased scrutiny and prominence. Objective. To highlight the health benefits of the Mediterranean diet as documented by studies undertaken mostly within a large countrywide general population cohort in Greece. Methods. The Greek EPIC (European Prospective Investigation into Cancer) cohort, a prospective study based on volunteers from the general population of Greece, and other investigations with converging objectives. In the Greek EPIC cohort of more than 28,000 volunteers being followed for more than 10 years, several findings on the association of diet with chronic diseases have been published in the international scientific literature. Results. The traditional Mediterranean diet of Greece is associated with reduced total mortality as well as reduced mortality from coronary heart disease and cancer. It is applicable in other Western populations, where it has also been shown to be inversely related to total mortality. Moreover, the traditional Mediterranean diet may be optimal for patients who have suffered a coronary infarct, and it does not promote obesity. Traditional foods are integral components of the Mediterranean diet and may contribute to its health-promoting attributes. The author is affiliated with the Department of Hygiene and Epidemiology, University of Athens Medical School, Athens, and the Hellenic Health Foundation, Athens. Please direct queries to the author at the Department of Hygiene and Epidemiology, University of Athens Medical School, 75 M. Asias Street, Goudi, GR-115 27, Athens, Greece; e-mail: [email protected]. A version of this paper was presented at the World Nutrition in Public Health Congress in Barcelona, 28–30 September 2006.

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Conclusions. The traditional Mediterranean diet may be an optimal diet both for healthy people and for patients with coronary heart disease and other chronic conditions.

Key words: Cancer, coronary heart disease, Greece, Mediterranean diet, mortality, traditional foods

The traditional Mediterranean diet and the Mediterranean diet score The traditional Mediterranean diet is the dietary pattern found in the olive-growing areas of the Mediterranean region in the 1960s. Although different regions in the Mediterranean basin have their own diets, several common characteristics can be identified, most of which stem from the fact that olive oil occupies a central position in all of them. It is therefore legitimate to consider these diets as variants of a single entity, the Mediterranean diet. Olive oil is important not only because of its several beneficial properties, but also because it allows the consumption of large quantities of vegetables in the form of salads and legumes in the form of cooked foods [1]. Over a period of 30 years, Ancel Keys and various collaborators of the famous Seven Countries study [2, 3] reported follow-up findings that were mostly focused on the role of diet in coronary heart disease. The dietary data were examined as subcohort averages, and the ecologic associations were interpreted as indicating that saturated fats could largely account for the variation in total cholesterol and, inferentially, the incidence of coronary heart disease. The argument of several scientists from Mediterranean countries that the diet of their region is more than a low-saturated-fat diet and has implications for diseases other than coronary heart disease had made little headway [4]. In the mid-1990s, a score was developed [5] to assess the degree of adherence to the traditional Mediterra-

Food and Nutrition Bulletin, vol. 28, no. 2 © 2007, The United Nations University.

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nean diet, which is characterized by high consumption of olive oil, vegetables, legumes, fruits, and cereals; regular but moderate ethanol intake, mostly during meals; low consumption of meat; and low to moderate intake of dairy products. The score was later revised to also include fish intake [6]. Persons whose consumption of beneficial components (vegetables, legumes, fruits, cereal, and fish) was below the median consumption were assigned a value of 0, whereas for individuals with consumption above the median, a value of 1 was given (see box 1 for scoring example). Scoring points were assigned in reverse for components presumed to be less favorable to health (meat and dairy products, usually consumed as whole fat in the Mediterranean region). For ethanol, a value of 1 was assigned to men consuming quantities from 10 g to less than 50 g per day, whereas for women the corresponding cutoffs were 5 and 25 g per day. Finally, for lipid intake, the ratio of monounsaturated to saturated lipids was used for countries of the Mediterranean region; for nonMediterranean countries, monounsaturated lipids were replaced by unsaturated lipids (monounsaturated plus polyunsaturated) in the numerator of the ratio. It should be noted that all evaluated intakes were adjusted for total energy intake. The total Mediterranean diet score could take a value from 0 (minimal adherence to the traditional Mediterranean diet) to 9 (maximal adherence to the traditional Mediterranean diet). Since 1995, variants of the Mediterranean diet score have been extensively used in studies around the world to assess adherence to this diet in relation to various health outcomes. There are several reasons for the BOX 1. Example of scoring Cutoff points in all instances (except for ethanol) are the median consumption, i.e., the quantity consumed by a person who, with respect to the particular food group, eats more than half of the people in the study eat and less than the other half eat. If a person, with respect to the median of the particular food group, consumes more vegetables (1), fewer fruits (0), more legumes (1), more meat (0), more fish (1), fewer whole-fat dairy products (1), fewer cereals (0), less than 5 g of ethanol daily (0), and plenty of olive oil in comparison with saturated lipids (1), the overall score for the person is 5. In all instances, intakes should be adjusted for total energy intake. The minimum score is 0 when a person consumes less than the median of all foods with “favorable” health effects and more than the median of all foods with “less favorable” health effects, according to current scientific knowledge, as well as either no alcohol or a large amount of alcohol. The maximum score is 9 when a person consumes more than the median of all foods with “favorable” health effects and less than the median of all foods with “less favorable” health effects, as well as reasonable quantities of alcohol.

widespread use of the scoring system in assessing various dietary patterns (both within and outside the realm of the Mediterranean diet), and all of them have to do with its being more discriminatory than the individual nutritional components. First, individual components may have small effects that become apparent only after their integration into a linear score. Second, biological interactions that could be discernible through the use of a simple linear score would otherwise require very large studies for their documentation. Third, when individual components are evaluated, effects are examined against the background of average risk generated by the other nutritional components, whereas a dietary score accommodates the extremes of cumulative exposure in the absence of other major nutritional effects [6–8]. In the following sections, the results of studies undertaken within the Greek EPIC cohort or in conjunction with it and evaluating adherence to the traditional Mediterranean diet in relation to various health outcomes will be summarized.

The Greek component of the European Prospective Investigation into Cancer The European Prospective Investigation into Cancer (EPIC) is conducted in 22 centers across 10 European countries under the coordination of the International Agency for Research on Cancer (IARC), with the purpose of investigating the role of biological, dietary, lifestyle, and environmental factors in the etiology of cancer and other chronic diseases. Between 1994 and 1999, a total of 28,572 volunteers 20 to 86 years of age were recruited from the general population of all regions of Greece in the context of the Greek component of EPIC. All procedures were in line with the Helsinki Declaration of Human Rights, all volunteers signed informed consent forms, and the study protocol was approved by ethical committees at IARC and the University of Athens Medical School. A validated, semiquantitative food-frequency questionnaire, including approximately 150 foods and beverages, was used to assess usual dietary intake over the year preceding enrollment. The questionnaire was administered in person by specially trained interviewers. For each of the items, respondents were asked to report their consumption frequency and portion size, the latter judged with the help of household units and photographs. Standard portion sizes were used for the estimation of consumed quantities, and nutrient intakes were calculated by using a food-composition database modified to accommodate the particularities of the Greek diet [9]. Eventually, 14 all-inclusive food groups or nutrients were considered: potatoes, vegetables, legumes, fruits, dairy products, cereals, meat, fish, eggs, monounsaturated lipids (mainly olive oil),

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polyunsaturated lipids (vegetable seed oils), saturated lipids and margarines, sugar and confectionery, and nonalcoholic beverages. For each participant, grams per day of intake of each of the indicated groups as well as the total energy intake were calculated. Overall mortality

Following the introduction of the score concept for the operationalization of the Mediterranean diet [5], several studies have used variants of this score in evaluating the association between adherence to the Mediterranean diet and total mortality [10–12]. Large studies, however, were undertaken within the Greek EPIC cohort [6], among aging Europeans in the context of the European EPIC-Elderly project [13], as well as in a cohort of Swedish women [8]. In all of these studies, closer adherence to the Mediterranean dietary pattern was associated with reduced total mortality. The inverse association was evident not only in Mediterranean countries [5, 6, 12, 13], but also in other European countries [8, 10, 13], as well as in Australia [11]. Meanwhile, other investigators have used more elaborate scores to assess adherence to the Mediterranean diet. Weighted and more complex scoring schemes are likely to be more discriminatory, but this comes at the cost of simplicity and general applicability of the instrument. Indeed, the simple score is applicable to most types of dietary questionnaires, including rudimentary ones.

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were comparable for mortality in the total cohort [6] and among patients with coronary heart disease [15]. Since, however, mortality—and specifically cardiac mortality—is substantially higher among patients with coronary heart disease than in the general population, it can be inferred that the Mediterranean diet is particularly beneficial among these patients. The beneficial effects of the Mediterranean diet on the prognosis of coronary heart disease have been demonstrated in two large, randomized secondary prevention trials [16, 17], but no observational study has previously addressed this issue. The results of the Greek EPIC study do not deviate from the findings of the randomized investigations, but they complement them by showing that alpha-linolenic acid (on which the randomized trials were anchored) may not be the central beneficial component in the Mediterranean diet and by indicating that there are alternative ways available to the general population to approach a Mediterranean dietary pattern. Mediterranean diet and risk factors for chronic diseases

The Mediterranean diet was introduced in the 1950s as the dietary pattern that confers protection against coronary heart disease [2]. Contemporary research on the Mediterranean diet has focused on total mortality. Few studies have focused on coronary mortality, total cancer mortality, or incidences of or mortality from specific forms of cancer. In the Greek EPIC cohort, the inverse association between the Mediterranean diet score and mortality was stronger for coronary mortality than for total cancer mortality, but even the latter association was statistically significant [6]. Outside the Greek EPIC, an inverse association with total cancer mortality was also reported in the Swedish cohort of young women [8], as well as in an ecologic evaluation [14].

An elegant randomized trial undertaken in Spain has provided powerful evidence that, in comparison with a low-fat diet, a Mediterranean diet rich in olive oil or nuts has beneficial effects on plasma glucose levels, systolic blood pressure, and blood lipid profiles [18]. Outside the “prescribing” setting of an intervention study, however, data from the Greek EPIC study have indicated that increased adherence to the Mediterranean diet is inversely associated with blood pressure, with olive oil driving this relation [19]. Moreover, data from the Greek EPIC cohort point to monounsaturated lipids—the key component of olive oil—as being the preferable lipids for the nutritional management of adult diabetes mellitus [20]. The Mediterranean diet has been criticized as possibly promoting obesity. In a study from the Greek EPIC cohort, when total energy intake was controlled for, adherence to the Mediterranean diet was unrelated to body-mass index in both sexes and was related to waistto-hip ratio only weakly and only in women [21]. Overweight, a genuine contemporary problem in Greece and perhaps other Mediterranean countries, mostly reflects the limited physical activity that characterizes the contemporary lifestyle patterns in the region.

Coronary survival

Traditional foods in the Mediterranean diet

In the Greek EPIC study, the association between adherence to the traditional Mediterranean diet and survival of more than 1,000 patients diagnosed with coronary heart disease was evaluated [15]. Higher adherence to the Mediterranean diet was associated with significantly lower overall and cardiac mortality among these patients. The effect estimates (rate ratios)

Traditional foods are an integral part of the Mediterranean diet, and it is necessary to investigate them not only to assess their potential contribution to the beneficial effects of this diet, but also to perpetuate important elements of the region’s cultural inheritance [22]. A series of studies run in parallel with the Greek EPIC cohort, but also in the context of national and

Cause-specific mortality

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European projects, has documented that wild greens and green pies, such as spinach pie and other traditional pies prepared with wild greens, are characterized by exceptionally high contents of several antioxidants, including a wide range of flavonoids [23–25]. In the international literature, including reports from casecontrol investigations conducted in Greece [26–28], the intake of antioxidants, particularly flavonoids, has been reported to be inversely related to the incidence of several chronic diseases.

Conclusions There is considerable evidence that the traditional Mediterranean diet may be an optimal diet for healthy people, as well as for patients with coronary heart disease and perhaps other chronic conditions. The traditional Mediterranean diet can be operationalized and investigated through the use of a simple unidimensional score. Traditional foods are integral parts of the Mediterranean diet and may contribute to its health-promoting effects.

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Mediterranean diet, traditional foods, and health: evidence from the Greek EPIC cohort.

For more than 50 years, the traditional Mediterranean diet has been considered health-promoting, but it was not until the mid-1990s that the topic beg...
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