Volume 55 Number 4 Supplement December 1998

Scientific basis of the healthy Mediterranean diet

Frank M. Sacks

Abstract It is now clear that the main problem with nutrition in industrialised countries, as well as in the more prosperous segments of developing countries, has shifted from nutritional adequacy to overnutrition--too much food in general, and a predominence of foods that are linked to cardiovascular disease or cancer. The incidence rates of cardiovascular disease and cancer, particularly those that are high in northern Europe, America, and Australia (colon, prostate and breast) are low in parts of Greece in which traditional dietary patterns are maintained. Favourable effects of Mediterrean diets on cholesterol and low density lipoprotein concentrations in the blood, as well as on blood pressure and hypertension, are likely to be one reason for the low coronary disease rates. The Lyon Heart Study used a traditional Mediterranean pattern to prevent death from coronary disease. The diet increased intake of vegetables, fruits, and fish which supplied vitamins such as folic acid, vitamin B6, carotenoids, and tocopherols, as well as oleic acid, alpha-linolenic acid, and other n-3 fatty acids. Thus the Mediterranean diet may be considered beneficial not only because of the reduced amount of saturated fat and cholesterol and increased mono-unsaturated fats, but because of micronutrients that act by mechanisms other than reducing blood cholesterol. For this reason, a worldwide group of scientists, clinicians, and health educators developed a dietary pyramid, based on traditional eating patterns in the Mediterranean, that reflected current science, and that had a goal to prevent cardiovascular disease and cancer. [Aust J Nutr Diet 1998;55(4 Suppl)S4-S7].

Does dietary intervention prevent coronary heart disease? An evidence-based review

Sandi Pirozzo, Paul Glasziou and Maxine Clark

Abstract The role of micronutrients, macronutrients and structural dietary change in cardiovascular disease is explored by examining the evidence from controlled randomised trials. Of the major micronutrients, it is clear that beta-carotene does not protect against cardiovascular disease and, in fact, may be harmful. The effects of alpha-tocopherol are inconclusive and the results of trials currently in progress may help to clarify its role in cardiovascular disease. Studies examining the effect of fish and fish oil have demonstrated a reduction in reinfarction and mortality, but little effect on restenosis following angioplasty. In relation to macronutrients, cholesterol reduction has shown to be highly protective in relation to all cause and cardiovascular mortality. However, dietary trials have not been as effective as drug trials in reducing cholesterol levels. Finally, structural dietary changes, in particular Mediterranean diets, have shown impressive results in relation to both all cause and cardiovascular mortality. [Aust J Nutr Diet 1998;55(4 Suppl)S7-S11].

Gene-diet interactions, plasma lipoproteins, and coronary heart disease: potential role of the apoAI-CIII-AIV gene cluster

Hannia Campos

Abstract For several decades there has been general consensus that high intakes of saturated fat increase plasma cholesterol levels and the risk of coronary heart disease (CHD). However, it is also quite evident that with similar diets, individuals vary substantially in their plasma lipid profile. Numerous gene variants or loci that are associated with CHD have been described. The results have been inconsistent, perhaps due to modest gene effects per se but more likely due to problems with study design such as low statistical power, the lack of a comparable control population to determine the underlying gene frequencies, and the lack of, or inadequate assessment of, dietary intake and other environmental factors such as body fat or physical activity. Most likely, dietary intake and genetic variant alleles act in combination to determine an individual's susceptibility, or resistance to CHD. In this report, the apoAI-CIII-AIV gene cluster as a potential modulator of the effect of dietary fat intake on plasma lipoproteins and the risk of CHD are examined. [Aust J Nutr Diet 1998;55(4 Suppl)S12-S15].

Mediterranean diet in secondary prevention of coronary heart disease

Michel de Lorgeril and Patricia Salen

Abstract The Lyon Diet Heart Study is a randomised secondary prevention trial aimed at testing whether a Mediterranean-type diet may reduce the rate of recurrence after a first myocardial infarction. This report presents results of a mean follow-up of 46 months per patient. Three composite outcomes (CO) combining either cardiac death and non-fatal myocardial infarction (CO 1) or the precedents plus major secondary endpoints (unstable angina, stroke, heart failure, pulmonary or peripheral embolism) (CO 2) or the precedents plus minor events requiring hospital admission (CO 3) were studied. In the Mediterranean diet group, CO 1 was reduced (14 events compared to 44 in the prudent Western-type diet group, P = 0.0001), as were CO 2 (27 events compared to 90, P = 0.0001) and CO 3 (95 events compared to 180, P = 0.0002). Adjusted risk ratios ranged from 0.28 to 0.53. The protective effect of the Mediterranean dietary pattern was maintained up to four years after the prior infarction. No noticeable side effect was observed. The data suggest that a low cost comprehensive strategy to reduce cardiovascular morbidity and mortality should primarily include a cardioprotective diet. [Aust J Nutr Diet 1998;55(4 Suppl)S16-S20].

The traditional Greek food pattern and overall survival in elderly people

Antigone Kouris-Blazos and Mark L. Wahlqvist

Abstract Evidence in support of the beneficial properties of the traditional Greek food pattern (TGFP) has recently become available. In prospective cohort studies of elderly people in rural Greece (n = 182), Greek-born (n = 189) and Anglo-Celtic Australians (n = 141), and Danes in Denmark (n = 202), it was found that adherence to the TGFP was associated with lower overall mortality and longer survival, irrespective of the types of foods consumed within food groups and the mode of food preparation. A higher TGFP score was significantly associated with a sharply reduced risk of death, by 17 to 23% per one unit increase and by more than 50% per four unit increase in the different cultural settings. Elderly Anglo-Celtic Australians had 80% higher mortality than the elderly Greek-born Australians; 37% of the excess mortality of the Anglo-Celts could be explained in terms of their different dietary habits and specifically their different extent of adherence to the TGFP. The key messages from these studies are: 1. a TGFP is beneficial to survival of elderly people; 2. the longevity of Mediterranean people can be explained in part by their varied diet; 3. the overall TGFP is more important for longevity than individual food groups; and 4. similar survival advantage can be obtained by applying the TGFP to other dietary cultures, irrespective of the types of foods consumed and the mode of food preparation. Whether or not further mortality benefit may have been obtained in the non-Greek cohorts if foods were prepared according to Greek cuisine, requires further study. [Aust J Nutr Diet 1998;55(4 Suppl)S20-S23].

Comparison of an Olive oil enriched diet to a Low fat diet Intervention study using Vascular Endpoints--assessed by repeat quantitative angiography (OLIVE Study)

David M. Colquhoun, Shawn Somerset, Paul Glasziou, Debbie Richards and Jeannet Weyers for the OLIVE study investigators

Abstract Epidemiological studies provide good evidence that a diet high in fat may be associated with low prevalence of coronary heart disease (CHD). Over 200 diet studies since the 1950s have unequivocally demonstrated that saturated fatty acid increases plasma cholesterol, while mono-unsaturated fatty acid (MUFA) and polyunsaturated fatty acid tend to lower plasma cholesterol. The OLIVE study is a randomised diet study of patients with CHD documented by coronary angiography. One hundred and eighty patients will be enrolled and undergo angiography at baseline and 2.5 years later. A low fat diet will be compared to a high fat Mediterranean-type diet rich in MUFA and enriched with olive oil. The low fat diet will have total fat providing less than 30% of energy. The Mediterranean diet will have 35% to 40% of energy as fat, with approximately 50% of fat being MUFA, which is typical of the Cretan diet in the 1960s. In addition patients will be randomised to alpha-linolenic acid (1.8 g) or placebo capsules (olive oil, 2 g). This is the largest trial of its type and the only trial to directly compare a low fat diet to a Mediterranean-type diet using angiographic end-points. Uniquely, it will assess the impact of psychological factors on progression of CHD. [Aust J Nutr Diet 1998;55(4 Suppl)S24-S29].

Energy balance: fats and fallacies

Linda C. Tapsell, G. Dennis Calvert, Barbara J. Meyer and Len H. Storlien

Abstract Strong evidence is accumulating that type, rather than amount, of dietary fat may be a key variable in the aetiology of obesity. A high saturated fat intake has been associated with development of obesity in many studies but polyunsaturated fats, and particularly those of the n-3 variety, may actually protect against accumulation of excess body fat with a number of potential mechanisms identified. Given the difficulties in persuading free-living individuals to change the macronutrient mix of their habitual diets, then more attention is warranted on the issue of getting the dietary fatty acid profile right. [Aust J Nutr Diet 1998;55(4 Suppl)S29-S32].

Dietary composition can influence patterns of regional fat loss

Kerin O'Dea and Karen Z. Walker

Abstract In this paper we summarise previously published evidence indicating that dietary composition can influence patterns of regional fat loss. This novel observation was made initially in the course of an outpatient study comparing the efficacy of two diets commonly prescribed for the treatment of type 2 diabetes: a high carbohydrate, high fibre, low fat diet, and a 'modified fat' diet containing a high proportion of mono-unsaturated fat. Both diets are low in saturated fat and therefore expected to be associated with a reduction in the risk of coronary heart disease. However, we were concerned that due to its relatively high fat content and energy density, the modified fat diet would be associated with weight gain when consumed in the free-living situation. In order to address this question, a randomised crossover design study was conducted in which subjects with type 2 diabetes consumed each diet for three months. Both diets were associated with moderate weight loss. The unexpected and significant finding was that the low fat diet was associated with a disproportionate loss of lower body fat, resulting in an adverse change in the ratio of upper to lower body fat. Loss of body fat during the modified fat diet was proportional, with no change in the ratio of upper to lower body fat. Furthermore, the modified fat diet was clearly preferred over the low fat diet. Studies are currently underway to elucidate the underlying mechanisms and gain further understanding of the significance of these findings. [Aust J Nutr Diet 1998;55(4 Suppl):S32-S36].