Association between the Mediterranean diet and cancer risk: a review of observational studies

The aim of this article was to summarize the evidence concerning the association between Mediterranean dietary pattern and cancer risk in observational epidemiological studies. All the studies that met the following criteria were reviewed: human cohort and case-control studies that examined the effect of the Mediterranean diet as an entire food pattern (the combined effect of individual components of the Mediterranean diet) and whose results were published in English. Out of the 12 reviewed studies (7 cohort and 5 case-control), 10 studies (6 cohort and 4 case-control) provided some evidence that the Mediterranean diet was associated with a reduced risk of cancer incidence or mortality. Although the reviewed studies varied according to certain study characteristics, such as being set in different populations and studying different cancer outcomes, the existing evidence from observational studies collectively suggests that there is a "probable" protective role of the Mediterranean diet toward cancer in general. Specific results for several outcomes such as different cancer sites deserve additional evidence. This favorable effect of the Mediterranean diet on cancer reduction is of public health relevance, given the tendency of modern societies to shift toward a more U.S. and Northern European dietary pattern.     

Mediterranean diet and longevity

Mortality statistics from the WHO database covering the period 1960 to 1990 have provided intriguing evidence that something unusual has been affecting in a beneficial way the health of the Mediterranean population. In recent papers, which evaluated the evidence accumulated over the last three decades, it was concluded that the traditional Mediterranean diet meets several important criteria for a healthy diet. Direct evidence in support of the beneficial properties of the Mediterranean diet has also become available. These data were derived from three studies, which have used a diet score, devised a priori on the basis of eight desirable key features of the traditional common diet in the Mediterranean region. The conclusion of these studies is that a diet that adheres to the principles of the traditional Mediterranean one is associated with longer survival. The Greek version of the Mediterranean diet is dominated by the consumption of olive oil and by high consumption of vegetables and fruits. Antioxidants represent a common element in these foods and an antioxidant action provides a plausible explanation for the apparent benefits. Wild edible greens frequently eaten in rural Greece in the form of salads and pies contain very high quantities of flavonoids-- considerably higher than those found in red wine or black tea. While there is no direct evidence that these antioxidants are central to the benefits of the Mediterranean Diet, indirect evidence from epidemiological data and the increasing understanding of their mechanisms of action suggest that antioxidants may play a major role.     

Olive oil and the Mediterranean diet

The high intake of olive oil in the Mediterranean diet contributes to the low intake of saturated fatty acids among populations in Southern Europe and is associated with a low incidence of coronary heart disease. Replacement of saturated fatty acids with oleic acid leads to a reduction in low-density lipoprotein (LDL) cholesterol without decreasing the concentration of high density lipoprotein (HDL) cholesterol. Oleic acid, however, may not be neutral with regards to its effects on risk of thrombosis which may have adverse consequences in populations with established atherosclerosis.     

Association between the prevalence of obesity and adherence to the Mediterranean diet: the ATTICA study

OBJECTIVE: We evaluated the prevalence of obesity in relation to adherence to a Mediterranean diet. METHODS: We conducted a cross-sectional survey that randomly enrolled 1514 men (18 to 87 y old) and 1528 women (18 to 89 y old) with no history of cardiovascular disease. Anthropometric indices were measured and frequency of various foods consumed during a usual week was recorded. Adherence to a Mediterranean diet was assessed by a diet score that incorporated the inherent characteristics of this diet. RESULTS: Prevalences of overweight and obesity were 53% and 20% in men and 31% and 15% in women. An inverse relation was observed between diet score, waist-to-hip ratio (r = -0.31, P < 0.001), and body mass index (r = -0.4, P < 0.001) after adjusting for sex and age. Greater adherence to the Mediterranean diet (i.e., highest tertile) was associated with a 51% lower odds of being obese (odds ratio 0.49, 95% confidence interval 0.42 to 0.56) and a 59% lower odds of having central obesity (odds ratio 0.41, 95% confidence 0.35 to 0.47) compared with a non-Mediterranean diet (i.e., lowest tertile) after controlling for age, sex, physical activity status, metabolism, and other variables. CONCLUSION: We observed an inverse relation between adherence to a Mediterranean dietary pattern and prevalence of obesity in a free-eating, population-based sample of men and women, irrespective of various potential confounders.     

Association between Mediterranean diet adherence and dyslipidaemia in a cohort of adults living in the Mediterranean area

The aim of the present study was to determine the association between Mediterranean diet adherence and dyslipidaemia in a cohort of adults living in the Mediterranean area. The cross-sectional study comprised a total sample of 2044 men and women, aged >18?years old from southern Italy. The Mediterranean diet adherence was assessed using a validated score (MEDI-LITE score). Clinical data were investigated and anthropometric examinations were collected using standardised methods. Among included individuals, 18.4% had dyslipidaemia. The percentage of females with dyslipidaemia was higher than males (21.2% vs. 14.6%). Higher adherence to Mediterranean diet was inversely associated with dyslipidaemia (OR: 0.56, 95% Cl: 0.36, 0.86). Similar association was observed in men, but not in women. On the contrary, a positive association was found between dyslipidaemia and current smoking and higher occupational status. Our results support the potential effectiveness of this diet in the prevention of dyslipidaemia and justify future intervention studies.     

Relationship between diet and blood pressure in a representative Mediterranean population

Summary. Background: Hypertension is strongly associated with cardiovascular and renal disease. However, despite the efforts made to control hypertension via drug treatment, prevalence of controlled hypertension could be considered low. Aim of the study: We performed the present study to investigate dietary habits among groups with different blood pressure status (normotensive, non-medicated hypertensive, medicated hypertensive) and to analyze the association between blood pressure and intakes of selected nutrients in normotensive and non-medicated hypertensive subjects (n = 1357), and furthermore in those undergoing hypertension drug treatment (n = 210; controlled and non-controlled). Methods: The present cross-sectional, population-based survey (Gerona, Spain) included cardiovascular risk measurements and analysis of dietary intake with corresponding questionnaires. Results: Nutrient intake was similar among groups of different blood pressure status after adjusting for sex, age and energy consumption. Multiple linear regression analysis, after adjustment for several confounders, showed that dietary intake of sodium was directly related to blood pressure. The same was seen for the sodium to potassium ratio and both were independent of hypertension drug treatment. In contrast, an inverse association was observed between blood pressure and dietary calcium intake. Moderate sodium (< 2400 mg Na/d) intake reduced the risk of hypertension by 30 % and 52 % (Odds ratio 0.70; 95 % CI 0.52–0.94, respectively) in normotensive and non-medicated hypertensive subjects. Furthermore, moderate sodium in combination with a calcium intake of more than 800 mg/d reduced the risk of inadequate blood pressure control, by 52 % (Odds ratio 0.48; 95 % CI 0.24–0.95) in subjects undergoing hypertension drug treatment. Controlled hypertension subjects have a significantly higher calcium intake than non-controlled. Conclusion: These results emphasize the importance of diet and overall of sodium intake as non-pharmacological approach in the prevention and treatment of hypertension. Received: 19 November 2001, Accepted: 20 June 2002     

Changing the Mediterranean diet: effects on blood lipids

A study was carried out on 48 healthy middle-age men and women habitually subsisting on a "Mediterranean type" diet in a rural area of southern Italy. Their freely chosen natural diet was modified for a period of 42 days by partially substituting animal fats for olive oil. Currently available foods were used, and the subjects maintained their habitual lifestyle. Dietary fat content changed from 33 to 37% of total energy and the polyunsaturated to saturated fatty acid ratio changed from 0.48 to 0.22. The base-line serum total cholesterol of men increased during the dietary intervention period from 214 +/- 30 mg/dl (mean and SD) to 245 +/- 33 mg (+15%). Low-density lipoprotein cholesterol increased 19%, while high-density lipoprotein cholesterol remained unmodified. Women, while exhibiting a similar trend in serum total cholesterol (+16%), showed also a 19% increase in their high-density lipoprotein cholesterol (p less than 0.001). Apoprotein B increased in parallel with low-density lipoprotein cholesterol in both sexes. The results of the study confirm the impact of the dietary factor on blood lipids. They also provide additional evidence on the response of high-density lipoprotein cholesterol to diet in free-living populations.