Researchers know that the func­tional abil­ity along with the quan­tity of high-​density lipopro­teins (HDL) or “good” cho­les­terol is needed for pro­mot­ing heart health. A new study finds the Mediterranean diet (MedDiet) increased HDL func­tion, and the improve­ments were larger if the eat­ing plan was aug­mented with an extra amount of vir­gin olive oil.

High lev­els of low-​density lipopro­teins (LDL) or “bad” cho­les­terol are linked to an increased risk of car­dio­vas­cu­lar dis­ease, while high lev­els of HDL are linked to a decreased risk. LDL pro­motes the buildup of plaque in the arter­ies, but HDL absorbs cho­les­terol and trans­ports it to the liver, where it is removed from the body. Therefore, HDL pro­vides the impor­tant ben­e­fit of help­ing to keep the blood ves­sels open.

“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 senior study author Montserrat Fitó, coor­di­na­tor of the Cardiovascular Risk and Nutrition Research Group at the Hospital del Mar Medical Research Institute in Barcelona and at the Ciber of Physiopathology of Obesity and Nutrition (CIBEROBN), Spain. “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.”

Since the func­tional prop­er­ties of HDL are so valu­able, researchers pur­posed to deter­mine what type of diet would enhance them. With this intent, they ran­domly chose 296 peo­ple at high risk of car­dio­vas­cu­lar dis­ease who were par­tic­i­pat­ing in the PREDIMED (PREvención con DIeta MEDiterránea) study.

The indi­vid­u­als, whose age aver­aged 66, were assigned to one of the fol­low­ing three diets for a year:

• A tra­di­tional MedDiet aug­mented with 4 table­spoons of vir­gin olive oil per day
• A tra­di­tional MedDiet aug­mented with a hand­ful of nuts per day
• A healthy con­trol diet that decreased intake of red meat, sweets, processed food and high-​fat dairy prod­ucts

Both MedDiets empha­sized the con­sump­tion of fruits, veg­eta­bles, legumes and whole grains, as well as included mod­er­ate amounts of fish and poul­try. Blood tests to mea­sure HDL and LDL were con­ducted at the begin­ning and end of the study.

Analysis of the find­ings showed only the con­trol diet low­ered total and LDL cho­les­terol. Although none of the diets boosted the lev­els of HDL sig­nif­i­cantly, both MedDiets improved its func­tion­al­ity. Moreover, the mag­ni­tude of this ben­e­fit was much larger among those who were on the MedDiet with the extra amount of vir­gin olive oil.

The MedDiet enriched with olive oil resulted in the func­tional HDL improve­ments below:

• Enhancement of the process by which HDL removes cho­les­terol from plaque in the arter­ies and sends it to the liver
• Increased pro­tec­tion against LDL’s harm­ful action of stim­u­lat­ing plaque devel­op­ment
• Boosted relax­ation of blood ves­sels, which kept them more open for the flow of blood

Because the extra quan­tity of olive oil was asso­ci­ated with the ben­e­fits in the study, it under­scored the stark con­trast between healthy and non-​healthy fat. “This study helps to seal in the idea that all fats should not be con­sid­ered equal,” Weston Childs, doc­tor of osteo­pathic med­i­cine in Gilbert, Arizona, told Olive Oil Times. “We know from stud­ies that most cook­ing oils on the mar­ket cause inflam­ma­tion and lipid dys­reg­u­la­tion by virtue of their effects on the omega 3:6 fatty acid ratio. The find­ing that a cold pressed oil, such as vir­gin olive oil, improved HDL func­tions shows the body metab­o­lizes these fats very dif­fer­ently.”

As the con­trol diet was rich in fruits and veg­eta­bles, like the MedDiets, the researchers were sur­prised it reduced the anti-​inflammatory prop­er­ties of HDL. A decline in this func­tion is linked to car­dio­vas­cu­lar dis­ease. Participants on both MedDiets didn’t have a reduc­tion in this area, the authors wrote.

“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,” con­cluded Fito. The study was pub­lished in the American Heart Association’s jour­nal Circulation.

• Circulation
• American Heart Association