A Low-Fat Vegan Diet May Lower LDL Cholesterol More than An Olive Oil-Enriched Diet

New research indi­cates that fol­low­ing a low-fat vegan diet with­out extra vir­gin olive oil may lower LDL cho­les­terol lev­els in indi­vid­u­als at high risk for car­dio­vas­cu­lar dis­ease more than a vegan diet sup­ple­mented with extra vir­gin olive oil.

The cross-over study, pub­lished in the Journal of the American Heart Association (JAHA), found that indi­vid­u­als lost more weight and demon­strated lower LDL cho­les­terol lev­els after fol­low­ing a low-fat diet than the olive oil-enriched diet. However, some promi­nent researchers have crit­i­cized the study design.

“There’s some con­tro­versy and debate in the car­dio­vas­cu­lar dis­ease world around the effect of veg­etable oils, includ­ing extra vir­gin olive oil, on risk fac­tors,” said Andrea Krenek, a researcher at the University of Florida and co-author of the study.

“Mediterranean diets usu­ally include a lot of extra vir­gin olive oil, while low-fat, plant-based diets often rec­om­mend avoid­ing it,” she added. ​“However, both diets are known to reduce heart dis­ease risk.”

“This hadn’t yet been stud­ied to our knowl­edge within a whole-food, plant-based vegan diet, so we aimed to design a study to inves­ti­gate this research ques­tion,” Krenek explained. ​“There hasn’t been much pre­vi­ous evi­dence aim­ing to eval­u­ate whether extra vir­gin olive oil specif­i­cally yields risk reduc­tion com­pared to the rest of the plant-based pat­tern.”

The trial involved 40 peo­ple who were at risk for ath­er­o­scle­rotic car­dio­vas­cu­lar dis­ease. They fol­lowed two vegan diets, each for four weeks with a one-week washout period.

In one diet, par­tic­i­pants used four table­spoons of California Olive Ranch extra vir­gin olive oil each day. They were instructed to con­sume the olive oil raw; oth­er­wise, no direc­tion was given on when or how to con­sume it. In the other diet, par­tic­i­pants were told to use as lit­tle olive oil as pos­si­ble, less than one table­spoon daily.

Both diets included whole fruits, veg­eta­bles, whole grains, legumes, nuts and seeds, exclud­ing ani­mal-based foods.

Between the two diet phases, par­tic­i­pants had a one-week washout period in which they were allowed to return to their usual eat­ing habits. This break is a com­mon research prac­tice to ensure that the first diet does not affect the results of the sec­ond one.

Researchers col­lected data on par­tic­i­pants’ metab­o­lism, clin­i­cal health, behav­ior and diet at the start and end of each diet period. As par­tic­i­pants fol­lowed each diet, researchers mea­sured how each affected them per­son­ally.

“Prior stud­ies have shown that the pro­cess­ing of olive oil, span­ning from refined to vir­gin to extra vir­gin, can impact lipid and inflam­ma­tory mark­ers, so we pro­vide extra vir­gin olive oil, which is also con­sumed in Mediterranean diets,” Krenek said.

The sci­en­tists found that both diets offered health ben­e­fits. ​“Both the high and low extra vir­gin olive oil diets reduced heart dis­ease risk fac­tors, includ­ing LDL cho­les­terol lev­els, com­pared to typ­i­cal diets that include ani­mal prod­ucts,” Krenek said.

LDL cho­les­terol is often called ​“bad cho­les­terol” because it deposits plaque in the artery, which can build up and increase the risk of heart dis­ease.

However, Krenek said there were sig­nif­i­cant dif­fer­ences between the two diets, par­tic­u­larly in key mark­ers for heart dis­ease risk.

“The low extra vir­gin olive oil diet yielded greater LDL cho­les­terol and lipid-low­er­ing com­pared to the high extra vir­gin olive oil diet,” Krenek said. ​“When eval­u­at­ing by diet order, those who started with the high extra vir­gin olive oil, then tran­si­tioned to the low extra vir­gin olive oil had a reduc­tion in LDL.”

“In con­trast, those who started with the low extra vir­gin olive oil, then added extra vir­gin olive oil for the sec­ond four weeks, low to high, had an increase in LDL,” she added. ​“This gave some inter­est­ing insight to inform future research ques­tions.”

Overall, both diets reduced sev­eral impor­tant health mark­ers related to heart health and inflam­ma­tion.

Participants in the study expe­ri­enced a reduc­tion in body weight dur­ing both diet phases, with more weight loss observed dur­ing the low-fat diet.

The researchers said the weight loss sug­gests that even within a whole-food, plant-based vegan diet, the amount of added fats, includ­ing extra vir­gin olive oil, can affect over­all energy bal­ance and sub­se­quent health mark­ers.

The researchers observed increased dietary fiber con­sump­tion dur­ing both diet phases, which they said helped lower LDL cho­les­terol.

They added that the shift to unsat­u­rated fats from whole foods and reduced sat­u­rated fats likely con­tributed to pos­i­tive health out­comes.

According to Krenek, the most inter­est­ing find­ings of the study include that ​“both low and high extra vir­gin olive oil within a whole food, plant-based vegan diet sup­port heart dis­ease risk reduc­tion com­pared to stan­dard omniv­o­rous pat­terns, though lower intake may yield greater lipid-low­er­ing com­pared to rel­a­tively greater intake.”

“The addi­tion of extra vir­gin olive oil after con­sum­ing smaller amounts may impede risk reduc­tion,” she added.

However, Mary Flynn, the founder of the Olive Oil Health Initiative of Brown University’s Miriam Hospital, cri­tiqued the study’s objec­tives and method­ol­ogy.

“Extra vir­gin olive oil does not typ­i­cally lower LDL cho­les­terol, and that has been known for a long time. Extra vir­gin olive oil will increase HDL and improve HDL func­tion,” she said. ​“Polyunsaturated fats will lower LDL more than monoun­sat­u­rated fats, but they will also oxi­dize the LDL, and oxi­dized LDL con­tributes to ath­er­o­scle­ro­sis.”

Flynn added that extra vir­gin olive oil’s pri­mary health ben­e­fits regard­ing car­dio­vas­cu­lar dis­ease come from its phe­nols and not the fat.

She pointed to the results of a 2023 review for which she was the lead author. The study found that ​“extra vir­gin olive oil can decrease LDL‑c for base­line val­ues greater than 120 mil­ligrams per deciliter and increase HDL‑c with a lin­ear increase with higher total phe­nol con­tent” com­pared with other dietary fats or low-fat diets.

“Diets includ­ing daily extra vir­gin olive oil are effec­tive for weight loss and long-term weight man­age­ment,” the researchers wrote. ​“In addi­tion, an extra vir­gin olive oil with a total phe­nol con­tent of at least 150 mil­ligrams per kilo­gram has been shown to decrease LDL oxi­da­tion.”

“While a diet that includes veg­etable seed oil may decrease LDL more than extra vir­gin olive oil, a diet that includes daily extra vir­gin olive oil will pro­duce health­ier LDL as the par­ti­cles will be larger and are less likely to be oxi­dized,” they added.

Flynn said one lim­i­ta­tion of the study pub­lished in JAHA was the lack of details about the olive oil used. Researchers did not pub­lish the phe­nol count, which Flynn said is essen­tial for any study inves­ti­gat­ing the rela­tion­ship between extra vir­gin olive oil and health out­comes.

Flynn also cri­tiqued the researchers’ assess­ment of caloric and nutri­ent intake. She said diet recall is not the best way to assess calo­ries since people’s mem­o­ries of what and how much they have eaten in the past 24 hours are known to be flawed.

Finally, she added that weight before and after both sets of tri­als in the cross-over study was not recorded, which makes it more dif­fi­cult to com­pare the results of the two diets for each group­ing.

“I don’t find the study use­ful,” she said. ​“It does­n’t add to the lit­er­a­ture in either direc­tion.”

“There’s a lack of knowl­edge sur­round­ing extra vir­gin olive oil, which is dri­ven by health poli­cies in this coun­try,” Flynn added, not­ing that the American Heart Association has long advo­cated for low-fat diets irre­spec­tive of the type of fat con­sumed.

“Extra vir­gin olive oil is a dif­fer­ent food. It’s the juice of the olive,” she said. ​“It’s the only food we have that has this range of health ben­e­fits. There’s no med­i­cine or no food that can com­pete with extra vir­gin olive oil.”

For her part, Krenek cau­tioned against over­sim­pli­fy­ing the results of the study.

“It’s always impor­tant to note big pic­ture diet con­text, pref­er­ences and risk level in prac­tice, as most peo­ple aren’t com­par­ing between extra vir­gin olive oil and sources of whole food fats, such as avo­ca­dos, nuts, seeds and olives,” Krenek said.

“The impact on risk fac­tors all depended on what was being com­pared,” she added, refer­ring to how the diets were mea­sured against the par­tic­i­pants’ usual eat­ing habits.

The researchers said this study high­lights the impor­tance of focus­ing on the types of dietary fats and food choices rather than just the amount of fats, car­bo­hy­drates and pro­teins.

They warned of a few lim­i­ta­tions of the study, includ­ing ​“a rel­a­tively short study period, a sam­ple of pre­dom­i­nantly well-edu­cated white women – future stud­ies are needed in larger, more diverse pop­u­la­tions – and car­ry­over effects, which means that the health sta­tus of par­tic­i­pants at the start of the sec­ond diet period was not the same as the first.”

The researchers believe that the next steps in study­ing this area should include expand­ing the research to dif­fer­ent pop­u­la­tions and vary­ing lev­els of heart dis­ease risk.