After a heart attack, the Mediterranean diet significantly reduces the risk of recurrence

Medications and invasive measures such as revascularization (stent placement) can save a large number of coronary patients, namely those who have suffered a myocardial infarction or another acute coronary syndrome. However, these patients generally remain at high risk of recurrence if they do not address the causes behind their coronary disease, which are in the majority of cases linked to certain aspects of their lifestyle (smoking, sedentary lifestyle, chronic stress, poor diet).

One of the factors that has received the most attention in recent decades is the nature of the diet. Given the role of saturated fat in the development of the plaques responsible for atherosclerosis (the blockage of the coronary arteries that leads to a heart attack), reducing dietary fat was established from the outset as the standard approach to reducing the risk of recurrence in coronary patients. These low-fat diets have evolved over time, in particular to include complex carbohydrates (whole grains, legumes) in order to obtain an adequate fibre intake, but aim first and foremost to reduce the total fat intake to 25-30% of daily calories and saturated fat to less than 10%.

The Mediterranean diet
We have repeatedly discussed the many studies that have clearly shown that the Mediterranean-style diet is associated with a reduced risk of cardiovascular disease. This diet is characterized by its high content of unprocessed plant foods (whole grains, vegetables, fruits, legumes, nuts and extra-virgin olive oil), a moderate intake of fish/shellfish and a low intake of red meat, deli meats, and fats of animal origin.

The main characteristic of the Mediterranean diet, however, remains the abundant use of extra-virgin olive oil as the main source of dietary fat, which can lead to a total fat intake of around 40% of total calories, well beyond that of low-fat diets used to reduce the risk of cardiovascular events in coronary patients. However, far from being problematic, this high intake of unsaturated fats seems on the contrary to be beneficial for the prevention of heart disease, both in primary prevention, in people who have no history of cardiovascular events, and in secondary prevention, in coronary patients who have already suffered a heart attack or who are at very high risk of suffering these events. For example, the results of the PREDIMED study show that a high intake of unsaturated fats, from nuts or olive oil, was associated with a significant decrease in the risk of cardiovascular disease. This protective effect of unsaturated fats was also observed in the Lyon study, carried out among 605 survivors of a myocardial infarction. The addition of linolenic acid (a short-chain omega-3 found in plants) to the patients’ diet caused a very significant reduction (73%) in recurrence of CV events after myocardial infarction, including cardiac mortality.

In other words, it seems that the nature of the fat in the diet matters much more than the amount and that a high intake of unsaturated fats could prove superior to a low-fat diet in significantly reducing the risk of cardiovascular disease, including in people at high risk due to a history of myocardial infarction. In the latter case, however, the concrete benefits of the Mediterranean diet on the risk of recurrence remain poorly understood since no large-scale study relating specifically to coronary patients has been carried out for nearly 25 years, i.e., since the Lyon study.

CORDIOPREV study
It is in this context that the results of the CORDIOPREV study, recently published in the prestigious journal The Lancet, come at the right time and could make it possible to reduce the high risk of recurrence that affect coronary patients. This study, carried out in Spain among 1002 patients with coronary disease who were followed for a period of 7 years, compared the impact of a “standard” low-fat or Mediterranean-style diet on patients’ risk of a cardiovascular event (myocardial infarction, stroke, revascularization, peripheral arterial disease or cardiovascular mortality).

The participants were randomly assigned to one of the two groups and supervised by a team of nutritionists to adhere as much as possible to their assigned diet (Table 1). For the low-fat group, the main instructions were obviously to limit the fat intake (vegetable oil, nuts, fatty fish, eggs) and to increase the intake of carbohydrate-rich foods (grains, legumes), while participants in the Mediterranean group were encouraged to increase their intake of unsaturated fats, mainly in the form of extra-virgin olive oil, nuts and fatty fish (salmon and sardines, for example). In both cases, participants were encouraged to consume 5 or more servings of fruits and vegetables and to limit the intake of red meat and deli meats (by favouring lean poultry as a source of meat), pastries and desserts, and sugary drinks.

Overall, these were two high-quality, plant-rich diets that were low in saturated fat (<10%) and simple sugars. The main difference between the two diets is the higher consumption of unsaturated fats in the Mediterranean diet, which reaches 40% of total calories (including 22% in the form of monounsaturated fat), while the low-fat diet is mainly composed of carbohydrates (46% of total calories) and relatively low in fat (32% of total calories, including 12% monounsaturated).

Table 1. Main dietary recommendations for the two study groups. Note that the main difference between the two diets is the higher amount of unsaturated fat (olive oil, nuts) consumed as part of the Mediterranean diet. *Sofrito is a preparation of vegetables and aromatics (herbs, garlic) cooked in olive oil over very low heat.

Cardiovascular protection
The results obtained show that this difference in the intake of unsaturated fats has significant repercussions on coronary patients’ risk of a cardiovascular event. The researchers observed that the “Mediterranean” group had an overall risk of events reduced by 27% compared to the “low-fat” group, a reduction which reached 33% in men (Figure 1). In people who adhered most closely to the Mediterranean diet, this protection is even 40%, which is considerable considering that these people are considered to be at very high risk of cardiovascular disease. These results therefore confirm the superiority of the Mediterranean diet over low-fat diets in reducing the risk of recurrence of cardiovascular events in coronary patients.

Figure 1. Comparison of the incidence of cardiovascular events in coronary men on a low-fat diet (blue) or a Mediterranean diet (red). Note the significant reduction (33%) in the risk of events associated with adherence to the Mediterranean diet. Taken from Delgado-Vista et al. (2022).

The protection offered by the Mediterranean diet observed in the study is particularly impressive for two reasons:

• Comparison with a high quality low-fat diet. The low-fat diet prescribed to the control group can be considered of excellent quality because of the abundance of plants (fruits, vegetables, legumes) and its reduced intake of saturated fats and simple sugars. Moreover, as noted by the authors, the mortality of this control group is reduced by half compared to what is usually observed in clinical trials with populations of coronary patients at high risk of recurrence. The ability of the Mediterranean diet to further reduce the risk of cardiovascular events compared to this high-quality control diet is therefore a shining example of the cardiovascular benefits associated with the Mediterranean diet.

• The health status of the patients enrolled in the study. These benefits are all the more striking in that they affect coronary patients at very high risk of recurrence due to the presence of a large number of risk factors affecting this population (Table 2).
  

Table 2. Main characteristics of the study population.

These patients were also heavily medicated, all of them being treated with statins or other cholesterol-lowering agents, 98% with anticoagulants, 83% with antihypertensives, and 80% with beta blockers. In other words, despite a fairly precarious state of health and aggressive medication, the adherence of these coronary patients to the Mediterranean diet still managed to significantly reduce the risk of cardiovascular events.

These observations illustrate the extent to which the adoption of a healthy lifestyle, particularly from a dietary perspective, can have a positive impact on cardiovascular health, even in people at very high risk.