Does the CORDIOPREV study really show that extra-virgin olive oil is heart-healthy?

By Dr Malcolm Mackay

CORDIOPREV is often presented as evidence that adding extra virgin olive oil to our diet is heart-healthy. More broadly, it’s presented as evidence that a high-fat Mediterranean diet is superior to a low-fat diet rich in complex carbohydrates for treating and preventing cardiovascular disease. Some plant-based advocates now regard EVOO as heart-healthy based on CORDIOPREV and other studies. We investigated the study findings and found that the diet interventions did not match the headlines. The study diets, as followed, were not the same as the diets recommended and reported in the abstracts. The main CORDIOPREV article (Delgado-Lista et al. 2022) did not provide the diet data for this study beyond calling it ‘Mediterranean and rich in EVOO.’  An earlier study, PREDIMED (also conducted in Spain), was even less transparent with diet data, only publishing it as supplementary data. Spain is the world’s leading olive oil producer and exporter.

The CORDIOPREV study compared a ‘Mediterranean’ diet with a ‘low-fat’ diet for secondary prevention of cardiovascular disease (i.e. preventing further cardiovascular events in patients with established coronary heart disease). The seven-year study of approximately 1000 predominantly male subjects was conducted in Spain. The subjects received dietary counselling and weekly deliveries of extra-virgin olive oil or an equivalent amount of low-fat food items. The lead publication (Delgado-Lista et al. 2022) concluded: “In secondary prevention, the Mediterranean diet was superior to the low-fat diet in preventing major cardiovascular events.”

The 7-year diet data revealed some interesting differences (see Cano-Ibanez et al. 2022). Firstly, the ‘low-fat diet’ group only reduced their fat intake to 32% of calories, stretching the definition of low-fat beyond most definitions. The ‘low-fat diet’ also failed to reach the target of at least 55% calories from (mostly complex) carbohydrates, only reaching 45.5%. Saturated fat intake was similar in the two groups, 7.9% for Med. and 7.1% for low-fat. Protein intake, predominantly animal protein, was 10% higher in the low-fat group, which may have contributed to their higher incidence of cardiovascular events.

The as followed diet data showed that the Mediterranean diet group did not just add olive oil but also increased their intake of whole plant foods. Overall, the dietary changes made by the two study groups were underwhelming. However, the Mediterranean diet group recorded a statistically significant greater increase in vegetables, fruits, nuts and legumes, and reductions in fish and dairy products. These changes alone may account for the observed decrease in CVD events in the Mediterranean group. Cereal intake decreased in both groups, an apparent failure in a study designed to have a high-carbohydrate diet group.

We expect a comparative diet study without an agenda to put equal effort into both groups’ diet quality and adherence. The two groups’ fruit, vegetable and legume intake should not have been allowed to diverge. Given that the Mediterranean diet group was supplied with extra virgin olive oil rather than everyday plain olive oil, it may have been a fairer comparison if the low-fat, high-complex carbohydrate diet group intervention had resulted in a substantially increased whole grain intake.

An additional arm of the CORDIOPREV study investigated the thickness of carotid artery plaque. There was a statistically significant reduction in plaque thickness in the Mediterranean group but no change in the ‘low fat’ group. However, the difference, 0.74 down to 0.71, was minimal, particularly when over 80% of patients were taking statins.

The seven-year cardiovascular outcomes in this study were poor in both diet groups despite most subjects taking statins. 17% of the Mediterranean diet group and 22% of the ‘low-fat’ group had further cardiovascular events. The individual patient might consider these odds unacceptable. The CORDIOPREV study is further evidence that heart disease still progresses on a Mediterranean diet rich in olive oil. The low-fat, whole-foods, plant-based diets prescribed by Ornish, Esselstyn, and Pritikin have documented far superior long-term cardiovascular outcomes including reversal.

See also:

• See our No Oil! page for a full explanation of why we recommend avoiding this calorie-rich and nutrient-poor food.
• Heart health section of our website

Resources

CORDIOPREV Research papers

Cano-Ibanez, N., Quintana-Navarro, G. M., Alcala-Diaz, J. F., Rangel-Zuniga, O. A., Camargo, A., Yubero-Serrano, E. M., . . . Lopez-Miranda, J. (2022). Long-term effect of a dietary intervention with two-healthy dietary approaches on food intake and nutrient density in coronary patients: results from the CORDIOPREV trial. European Journal of Nutrition, 61(6), 3019-3036.

Delgado-Lista, J., Alcala-Diaz, J. F., Torres-Pena, J. D., Quintana-Navarro, G. M., Fuentes, F., Garcia-Rios, A., . . . Investigators, C. (2022). Long-term secondary prevention of cardiovascular disease with a Mediterranean diet and a low-fat diet (CORDIOPREV): a randomised controlled trial. Lancet, 399(10338), 1876-1885.