Mediterranean diet may improve HDL function

After one year, adults with high cardiovascular risk who adhere to a Mediterranean diet had improvements in several high-density lipoprotein (HDL) functions, according to a randomized trial.

The improvements were particularly evident when the Mediterranean diet was enriched with virgin olive oil. The researchers mentioned the Mediterranean diet includes fruit, vegetables, legumes, whole grains, fish and poultry.

Lead researcher Álvaro Hernáez, PharmD, MSc, of Hospital del Mar Medical Research Institute in Barcelona, and colleagues published their results online in Circulation on Feb. 13.

In this study, known as PREDIMED, the researchers evaluated 296 adults who had biological samples at baseline and after a year of the dietary intervention. At baseline, the participants were randomized to a Mediterranean diet enriched with virgin olive oil, a Mediterranean diet enriched with nuts or a low-fat control diet.

The baseline characteristics were similar in all three groups. The mean age was approximately 66 years old, the mean body mass index was 30 kg/m2 and the mean waist circumference was 39.4 in. (100 cm).

The researchers found that both of Mediterranean diets increased cholesterol efflux capacity. Meanwhile, the Mediterranean diet enriched with virgin olive oil decreased cholesterol ester transfer protein activity and increased HDL ability to esterify cholesterol, paraoxonase-1 arylesterase activity and HDL vasodilatory capacity. In addition, all three diets increased the percentage of large HDL particles. Further, the control diet had a negative impact on HDL’s anti-inflammatory properties, which is associated with cardiovascular diease.

“The present work could contribute to the discovery of novel therapeutic targets that may improve HDL function in humans (new antioxidant-rich functional foods, nutraceuticals, or new drug families),” the researchers wrote.

The researchers mentioned a few limitations of the study, including that they only enrolled elderly people at high cardiovascular risk, so the results might not be generalizable to other groups. They also mentioned using cellular models might not have demonstrated the effect of contraregulatory mechanisms. In addition, they could not perform the analyses related to HDL main enzymatic proteins at two study centers, could not assess HDL size at one study center and could not perform HDL vasodilatory capacity analyses in 16 percent of the participants due to technical issues in cell cultures.

“Our data support the improvement in HDL function after following a [Mediterranean diet],” the researchers wrote. “Further studies are warranted to investigate the mechanism by which the [Mediterranean diet] improves HDL function and whether these properties convey cardioprotective effects.”