As a staple of plant-based diets like the Mediterranean diet, olive oil has long been lauded for its ability to lower heart disease risk. A recently published University of Florida study, however, suggests other elements of that diet may play a greater role in achieving health benefits.

The Recipe for Heart Health study is the culmination of collaboration between researchers from the UF/IFAS food science and human nutrition department, the UF Division of Cardiovascular Medicine, and the National Institute of Diabetes and Digestive and Kidney Diseases. Published in the Journal of the American Heart Association, the nine-week study followed 40 adults between 18 and 79 for 11 months. The participants had various health factors that met classifications for placing them at risk for cardiovascular disease.

During the study, all participants adhered to whole-food, plant-based, vegan diets, but they were randomly assigned to consume either a “low” amount (less than a teaspoon) or a “high” amount (4 tablespoons) of extra virgin olive oil (EVOO) each day for four weeks. After a one-week “washout” period, the participants switched and followed the other EVOO regimen for four weeks.

Cooked olive oil can produce inflammatory compounds, depending on temperature, so study participants were instructed to consume raw olive oil. Many did so by adding it to salad dressings and sauces. They abstained from eating animal products and heavily processed and refined food and instead ate whole fruits, vegetables, legumes, whole grains, nuts and seeds. The researchers encouraged nutritionally balanced meals, but they did not control portion sizes or caloric composition of meals.

Neither regimen was low in fat; participants obtained at least 30% of their energy from dietary fat, whereas dietary fat would have contributed to between 10 and 15% of their energy if they had followed a typical low-fat diet, said Andrea Krenek, the study’s lead author and a registered dietitian nutritionist with the UF/IFAS food science and human nutrition department.

During the high-EVOO phase, participants obtained most of their dietary fat from EVOO. During the low-EVOO phase, they primarily obtained it from unrefined, whole, plant-based fats such as avocados, nuts, seeds and olives.

Compared to baseline levels, consuming both high and low amounts of EVOO resulted in decreased levels of LDL, or “bad,” cholesterol, which has been linked to heart disease. But participants experienced greater reductions in LDL cholesterol after four weeks of the low-EVOO regimen.

And the order participants followed the regimens mattered. Those who started with the high-EVOO regimen and then transitioned to the low-EVOO regimen achieved decreased LDL. Those who started with the low-EVOO regimen and transitioned to the high-EVOO regimen saw their LDL levels increase compared to what they were upon ending the low-EVOO regimen.

“This study suggested that while a whole-food, plant-based diet with or without extra virgin olive oil may lower heart disease risk factors compared to a standard omnivorous diet, a lower amount of extra virgin olive oil while incorporating other whole forms of dietary fat may yield greater risk reductions,” Krenek said.

Emphasizing whole-plant foods while limiting foods that may increase risks – such as red and processed meats, added sugars and saturated fats – likely plays a greater role in the benefits of plant-based diets than consuming EVOO alone, she explained.

Krenek said her team plans to use data from the study to produce additional research articles on cooking, diet quality, mood and quality of life.