Cardiovascular Diseases and Nutrition
Serge RENAUD University Bordeaux 2 - France

Cardiovascular diseases are the main cause of morbidity and death in the industrialized countries, especially in aged people. Their relationship to diet has been already observed at the end of 19th century when atherosclerosis was induced in animals, by giving saturated fats and cholesterol to rabbits. In 1933 it was confirmed that populations consuming a high amount of saturated fats presented atherosclerosis and coronary heart disease (CHD). Finally in the 1960's, Ancel Keys, through the Seven Country Study, gave the evidence that the intake of saturated fat was the main environmental factor for CHD. Nevertheless, to demonstrate the role of saturated fats in the pathogenesis of CHD, randomized intervention trials in man were required to be reasonably certain of their detrimental effect. In that connection, saturated fats had to be replaced in the diet, by some other nutrients or foodstuffs. The suggestion was to replace saturated fatty acids by polyunsaturated fatty acids, that lower cholesterol, the principal hypothesis through which saturated fats were atherogenic. The main polyunsaturated fatty acid that lowers cholesterol is linoleic acid (18:2 n-6). Thus in the first intervention trials to test whether a diet, lower in saturated fat, could protect from CHD, part of the saturated fatty acids were replaced by linoleic acid. Interventions with such diets, both in primary or secondary prevention, fail to show the expected significant protective effects on fatal and non fatal CHD.
These results have been disastrous for nutrition. A majority of physicians considered it was the demonstration that diet was not involved in CHD clinical manifestations and other serious health problems. It has to be emphasized that in earlier work with diet Scientists were more or less playing "Sorcerer Apprentice". Still, it was known that populations protected from CHD such as Japanese in Japan (the greatest life expectancy in the world) and Cretans, in Crete (the greatest life expectancy in the Western World), do not have a high intake of linoleic acid. Their intake in saturated fat is low (approximately 8 % energy) but replaced by cereals, vegetables and oleic acid, especially in Crete (olive oil) and a proper balance of the two families of polyunsaturated fatty acids n-3 and n-6. The main precursor of the n-3 family is alpha-linolenic acid (ALA) and of the n-6 family, linoleic acid. Prospective studies and intervention trials have shown that the n-3 fatty acids, mostly ALA, markedly lower the risk of cardiac death (sudden death) and non-fatal myocardial infarction.
In addition to fats and fatty acids, foodstuffs such as cereals, fruit, vegetables and even alcohol may play important roles that were neglected in the earlier work on the relationship between diet and cardiovascular diseases. The diet proposed nowadays (1), that includes most of the foodstuffs recently shown to have protective effects on CHD, is simply an adaptation of the Mediterranean diet and other natural diets, still highly palatable, even gourmet diets. Of additional interest is that in intervention trials, these dietary protective effects on the main clinical manifestations occur rapidly (within a few weeks) after diet modification. From the public health point of view, such dietary changes have been adopted by Finland in the last 25 years, with a reduction of more than 60 % in the mortality rate from CHD, stroke and even cancer.
The reasons why diet works so efficiently are that many nutrients act distinctly, several times per day, on the various targets associated with CHD, stroke and other diseases. As examples, the essential fatty acids regulate platelet reactivity but also prevent arrhythmia by stabilizing myocite membrane as platelet membrane and any other cell membrane. Fruit and vegetables supply antioxidants required for every function in the body.
In the present special issue of the J.N.H.A. expert Scientists from different countries have briefly reviewed, at the light of new discoveries, some of the important topics related to the role of diet and nutrients in cardiovascular diseases. Recent intervention studies suggest that the efficient diet to prevent cardiovascular diseases has been finally discovered after a century of hard work, in different fields. Nevertheless, most of the current results have to be confirmed. In addition, many additional nutrients may be involved in the spectacular protective effects of diet, and mechanisms of their effects need to be further investigated, to definitely remove any doubts concerning the health effects of a simple, but well balanced diet (2).

References

1. Renaud S, Lanzmann-Petithory D. Coronary heart disease: dietary links and pathogenesis. Public Heath Nutrition 2001 (in press).
2. Kris-Etherton P, Eckel RH, Howard BV, St Jeor S, Bazzare TL. Lyon Diet Heart Study. Benefits of a Mediterranean-Style, National Cholesterol Education Program/American Heart Association Step 1 Dietary Pattern on Cardiovascular Disease. Circulation 2001;103:1823-7.