First-of-Its-Kind Study Challenges the Health Halo of Olive Oil

An important new study provides compelling evidence that while olive oil is healthier than animal-based fats, no oil may be the healthiest of all when it comes to heart health. The study, published last week in the Journal of the American Heart Association, is one of the first to compare a whole-food, plant-based (WFPB) diet that contains olive oil with a WFPB diet that contains little to no oil.

Olive oil first gained a reputation as a health food in the 1990s, with the popularization of the Mediterranean diet—a plant-forward eating pattern that emphasizes fruits, vegetables, and whole grains, with modest amounts of dairy, eggs, fish, and poultry, and with olive oil serving as the primary source of added fat. Cultures with Mediterranean diets have lower rates of heart disease, metabolic disease, Type 2 diabetes, and other chronic health conditions. But which aspects of the Mediterranean diet confer the greatest health benefit is an area of ongoing investigation. While a number of studies have corroborated the benefits of emphasizing fruits, vegetables, and whole grains and minimizing red meat, the role of olive oil is less clear.

“There is a lot of important data from Mediterranean diet studies that show that a primarily plant-based diet with [extra virgin olive oil] is better than an animal-based diet,” says cardiologist Monica Aggarwal, M.D., who co-authored the new study. But, as Aggarwal and her co-authors note in the study, there has been little data around whether a plant-based diet without oil might offer even greater heart-health benefits. So Aggarwal and a team of researchers from the University of Florida and National Institutes of Health set out to investigate.

Dubbed the Recipe for Heart Health Trial, the study included 40 adults at risk for cardiovascular disease. None of the participants were plant-based before the study; all were omnivores. The researchers split them into two groups: One group consumed a whole-food, plant-based diet that included 4 tablespoons of extra-virgin olive oil daily. The other group consumed a WFPB diet that was virtually oil free, containing no more than 1 teaspoon of olive oil daily. After four weeks, the researchers had them switch diets. They received gift cards for groceries and attended dietitian-led virtual cooking classes throughout.

Before and after each phase of the trial, the researchers ran blood work and measured aspects of cardiometabolic health including cholesterol, triglycerides, blood sugar, and high-sensitivity C-reactive protein (an inflammation marker that can predict the risk of heart disease).

Compared with their blood work at the start of the study, participants saw improvements in cholesterol and other heart health markers while on both plant-based diets, but they saw greater improvements on the low-oil plant-based diet. And when participants switched from the low-oil phase to the higher-oil phase, they saw increases in cholesterol, triglycerides, blood sugar, and hs-CRP.

The authors conclude that “although both inclusion and exclusion of extra virgin olive oil within a whole food, plant-based vegan diet support cardiometabolic disease risk reduction compared with a standard omnivorous pattern, decreased intake of extra virgin olive oil may yield increased lipid lowering than relatively greater consumption.”

This latest study adds to growing evidence that olive oil—which is pure liquid fat, with most other nutrients, including fiber, stripped away—is not a health food.

Prominent whole-food, plant-based physicians such as Caldwell Esselstyn, M.D., have long recommended consuming low-fat WFPB diets with little to no added oils for optimal heart health. In 2019, Esselstyn authored an editorial in the International Journal of Disease Reversal and Prevention highlighting scientific evidence linking oil consumption with damage to the arteries.

A 2022 study made headlines when it found that participants who consumed olive oil on a daily basis were less likely to die of cardiovascular disease and all other causes than those who never or rarely consumed olive oil. But that study only analyzed death rates based on different types of added fat in the diet. It did not look at diets with little to no added fat. As Neal Barnard, M.D., president of the Physicians Committee for Responsible Medicine, explained at the time on The Exam Room by the Physicians Committee podcast: “Olive oil is better than chicken fat, beef fat, cheese fat, dairy fat. … Chicken fat is 30% saturated fat. Beef is 50% saturated fat. But for olive oil it’s all the way down to 14%. That’s good,” Barnard said. “But what if instead I get a nonstick pan and I don’t use any fat at all? That’s best of all because every gram of fat, no matter where it’s from, has 9 calories, and our research has shown that when people get away from these fats in general they do best of all.”

Matthew Lederman, M.D., co-author of The Forks Over Knives Plan, says that the new study’s findings are in line with results he’s seen among patients who adopt oil-free plant-based diets, with even greater improvements among those who adhere to a low-fat plant-based diet in which only 10%–15% of calories come from fat. “We can see total cholesterols drop 50 points [in weeks],” says Lederman.

Lederman hopes that the recently published research will help shift the perception of olive oil. “This study is not saying you can’t ever have oil, but don’t try and kid yourself that it’s a health food,” he says. For those who aren’t ready to cut out oil completely, Lederman recommends minimizing it as much as possible. “Use it as a last resort,” he says. “Push yourself to make dishes using other sources of rich fatty flavors and textures, like avocados, nuts, seeds, olives. Get it from a whole food if you can.”

To learn more about a whole-food, plant-based diet, visit our Plant-Based Primer. For meal-planning support, check out Forks Meal Planner, FOK’s easy weekly meal-planning tool to keep you on a healthy plant-based path.