The 'diet heart' hypothesis in secondary prevention of coronary heart disease.

From this detailed analysis of the main dietary trials conducted over the last 30 years in the secondary prevention of coronary heart disease, it can be said that the older trials were conducted on low risk patients and used high fat diets (about 40% of energy as lipids), comprising low saturated fat and cholesterol intake but very high (15 to 20% of energy) polyunsaturated fat intake, particularly from the omega-6 fatty acid family. These experimental diets were designed to reduce blood cholesterol and failed to improve prognosis. By contrast, recent trials were not primarily designed to reduce cholesterol, were conducted in medium- and high-risk patients and used low fat diets supplemented by omega-3 fatty acids from various sources. In two of these trials, the consumption of natural antioxidants, oligoelements and vegetable proteins was increased. Recurrence rate was reduced in the range of 30 to 70%. One conclusion from these well-conducted recent experiments on more than 3000 patients is that new and more specific dietary recommendations are clearly warranted in secondary prevention of coronary heart disease. They should be more specific and more clearly defined and therefore different from those generally provided in the U.S.A. and Europe at present. In a recent Consensus Panel statement, authors wrote less than one line to describe a cardioprotective diet in patients with coronary heart disease, summarized as < or = 30% fat, < 7% saturated fat, < 200 mg.day-1 cholesterol. This is both too much (too restrictive to hope that white European and American patients will adhere in the long-term) and insufficient because dietary counselling cannot be restricted to three factors. Ulbricht and Southgate recently emphasized that the relationship between diet and coronary heart disease is more complex than the current cholesterol hypothesis. They identified at least seven major dietary factors, including fibres, although the evidence of an effect on coronary heart disease is weak. However, they did not mention vegetable and fish proteins which are rich in arginine and L-glutamine, major regulators of cardiovascular function. Thus, new dietary advice should include: reduce intake of total (not more than 30% of energy) and saturated (less than 10%) fats maintain intake at least minimally, of the essential omega-6 fatty acids augment consumption of oleic acid and moderately increase consumption of omega-3 fatty acids augment intake of natural antioxidants and oligo-elements maintain sufficient intake of vegetable proteins As conceptualized in the 'Mediterranean' and 'Asian-vegetarian' types of diet, it is very important that a healthy diet should be thought of as a whole rather than as a recitation of good and bad components. Although these protective dietary modifications should probably all be used in each patient to obtain maximal efficacy, these scientifically quantitated principles should be adapted to the culture, ethnic origin and 'image of the world' of each patient in order to create an environment favourable to the perception of positive associations between various foods and healthy habits.