In Germany, cardiovascular diseases are the leading cause of death. However, the risk varies from person to person. Besides family history, important factors include lifestyle and certain dietary habits. The PREDIMED study was able to prove that the Mediterranean diet can protect against the development of cardiovascular disease when compared to a low-fat diet. However, this was only proven in the context of primary prevention, in other words in patients without a pre-existing cardiovascular disease. It is still unclear whether the Mediterranean diet has a similar effect on patients with pre-existing cardiovascular conditions. In 2009, the CORDIOPREV study was launched to clarify this question. While it is still ongoing, the first data have already been analysed. A team led by the scientist Jose Lopez-Miranda from Spain investigated whether the Mediterranean diet has an influence on the progression of arteriosclerosis.
To this end, the research team analysed data already collected from the 1,002 participants of the CORDIOPREV study. All participants suffered from stable cardiovascular disease at the start of the study with the last event occurring more than six months prior to inclusion. Of the subjects, half were instructed to follow a Mediterranean diet from then on. The other half followed a low-fat diet.
As expected, participants in the Mediterranean diet increased their intake of monounsaturated and polyunsaturated fatty acids and fibre, but reduced their intake of saturated fats, carbohydrates and cholesterol. The opposite was true for the participants of the low-fat diet. They consumed more carbohydrates and fibre, but less unsaturated fatty acids and cholesterol.
The participants received an ultrasound examination of the carotids in the baseline phase and after 5 and 7 years with the aim of measuring the intima-media thickness (IMT). IMT is a non-invasive marker for determining the presence of subclinical atherosclerosis. It can also be used to estimate cardiovascular risk quite accurately. The researchers then examined whether there were differences in IMT between the two diet groups. Known confounders such as age, gender, nicotine consumption, body weight, comorbidities and use of medication were taken into account during the analysis.
The group on the Mediterranean diet experienced a significant decrease in IMT after 5 years (- 0.027 mm, p < 0.001). This trend even continued to some extent after 7 years (- 0.031 mm, p < 0.001). In the low-fat diet group, however, IMT remained largely unchanged during the observation period. The difference in IMT was substantial between both groups and at both points in time (5 and 7 years). The number of carotid plaques was not affected by either diet and remained stable.
The researchers were also interested in the influence of both diets on the fatty acid profile in the blood. In both groups, the proportion of monounsaturated fatty acids increased. However, this increase was more pronounced in the Mediterranean diet due to the increased concentration of oleic acid (p = 0.008). Both of the diets also increased the levels of polyunsaturated fatty acids. Surprisingly, however, the subjects on the low-fat diet had higher levels, which can be attributed to an increased concentration of linoleic acid (p < 0.001).
The study shows that a Mediterranean diet can have a significant impact on the development of atherosclerosis in patients with pre-existing cardiovascular disease, as measured by the IMT. Other evaluations of the CORDIOPREV study had already provided similar indications. For example, the Mediterranean diet was shown to improve endothelial function in patients with existing cardiovascular disease. Now only the "hard endpoint data" are missing, which will hopefully prove that a Mediterranean diet rich in olive oil, fish, vegetables and nuts also leads to a significant reduction in cardiovascular events in this patient group. The data are eagerly awaited.
Sources:
Jimenez-Torres et al. Mediterranean Diet Reduces Atherosclerosis Progression in Coronary Heart Disease: An Analysis of the CORDIOPREV Randomized Controlled Trial. Stroke. 2021;52:3440–3449. 10 Aug 2021.