Mediterranean Diet May Reduce Cardiovascular Risks

Patients consuming a Mediterranean diet enriched with olive oil showed improved HDL function.

A Mediterranean diet enriched with virgin olive oil may boost the function of high-density lipoprotein (HDL) in patients at risk of compared with other diets, according to a new study published by Circulation.

This diet was seen to remove excess cholesterol from the arteries, act as an antioxidant, and keep blood vessels open, which all reduce the risk of developing heart disease.

High levels of low-density lipoproteins (LDL), also known as bad cholesterol, and triglycerides are known to increase the risk of heart and blood vessel diseases. In contrast, HDL cholesterol removes excess cholesterol from the blood and reduces health risks.

"However, studies have shown that HDL doesn't work as well in people at high risk for heart attacks, strokes and other cardiovascular diseases, and that the functional ability of HDL matters as much as its quantity," said study senior author Montserrat Fitó, MD, PhD. "At the same time, small-scale trials have shown that consuming antioxidant-rich foods like virgin olive oil, tomatoes and berries improved HDL function in humans. We wanted to test those findings in a larger, controlled study."

Included in the study were 296 patients at high risk of developing cardiovascular disease who were participating in the PREDIMED study. Blood samples were taken at baseline and the conclusion of the study.

Patients were randomized to consume 1 of 3 diets for 1 year: traditional Mediterranean diet enriched with virgin olive oil (4 tablespoons per day); a traditional Mediterranean diet enriched with extra nuts (a fistful per day); or a healthy control diet, which reduced the intake of red meat, processed food, high-fat dairy products, and sweets.

For the traditional Mediterranean diet, participants were encouraged to eat fruit, vegetables, legumes, and whole grains, fish, and poultry, according to the study.

Interestingly, the researchers found that only the control diet reduced total and HDL cholesterol levels, while none of the diets increased HDL levels significantly. The Mediterranean diets were both found to improve HDL function, but the diet rich in olive oil improved function the most significantly, according to the study.

The authors found that patients in the olive oil enriched diet group had greater antioxidant protection, meaning that HDL counteracted LDL oxidation, which is known to cause plaque development. They also discovered that HDL cholesterol had improved ability to remove cholesterol from arterial plaque, and transport it to the liver.

Patients in the olive oil-enriched diet group also were observed to have better vasodilator capacity, which relaxes blood vessels and improves blood flow.

The study authors were surprised to discover that the control diet had a negative impact on the anti-inflammatory properties of HDL, which is linked to cardiovascular disease, according to the study. However, patients following a Mediterranean diet did not experience a decline in HDL function.

The investigators indicated that the differences in results were small, since there was minimal modification of the Mediterranean diets and the control was healthy. They also noted that the results are focused on patients at high risk of developing cardiovascular disease who would benefit most from the intervention, according to the study.

“Following a Mediterranean diet rich in virgin olive oil could protect our cardiovascular health in several ways, including making our 'good cholesterol' work in a more complete way,” Dr Fitó concluded.