Could frying vegetables in olive oil be the healthiest way to cook them?

That’s the suggestion of a recent Spanish study. It found that sautéing vegetables—even frying them—in extra-virgin olive oil resulted in dishes that were richer in certain health-promoting compounds than leaving them raw or boiling them.

But don’t start frying all your veggies just yet. There’s more to the story.


In the study, researchers at the University of Granada in Spain looked at four vegetables commonly found in the Mediterranean diet—tomato, eggplant, pumpkin and potato. They cubed them and then cooked them different ways—boiled in water, boiled in water plus extra virgin olive oil (EVOO), sautéed in EVOO or fried in EVOO.

Then they measured levels of phenols in the cooked foods as well as in the raw foods. Results: Frying and sautéing in olive oil yielded the most phenols in the finished dish—significantly increasing both the total amount and the healthful variety of these compounds. Boiling in water, or even water with a little olive oil added in, didn’t increase phenols. It was the direct heating of veggies in olive oil that made the difference.

What’s so great about phenols? These antioxidant compounds, found in many plant foods (fruits, vegetables, the olives that get turned into olive oil, even champagne) protect the body’s cells against oxidation and inflammation that can promote chronic disease. People whose diets are rich in phenols are statistically less likely to develop heart disease, Alzheimer’s disease and certain cancers.

To put the new research in perspective, we spoke with Sharon Palmer, RDN, a registered dietician based in Los Angeles who is author of The Plant-Powered Diet and Plant-Powered for Life. “Health experts once thought that boring, zero-fat, steamed veggies were the way to go,” she said. “But more research is pointing to the advantages of cooking your vegetables in extra-virgin olive oil.”


One way that cooking in olive oil enhanced phenols  in the study was that it helped make them easier to absorb. This didn’t surprise Palmer. “Other studies have also found that certain antioxidant compounds and nutrients in some vegetables become more bioavailable to your body in the presence of olive oil.”

But some of the extra phenols in the cooked dishes came not from a change in the vegetables’ phenols, but from additional phenols added from the olive oil itself. You’d get similar benefits from simply including EVOO in your diet—in your salad dressing, for example. You don’t need to fry everything! “Olive oil is rich in many phenolic compounds,” says Palmer. “A body of science backs up the benefits of eating a Mediterranean diet, which includes a generous dose of extra-virgin olive oil—in a diet filled with minimally processed foods such as grains, vegetables, fruits, legumes, herbs, nuts and seafood.” In one major study, called PREDIMED, she notes, each increase of 10 grams a day in EVOO—about two teaspoons—was associated with a 10% reduction in risk for cardiovascular events. Now that’s impressive!

What’s so special about the golden nectar that is extra-virgin olive oil? Because extra-virgin olive oil is minimally processed, it retains many of those phenolic compounds present in the olive. And it is rich in heart-healthy monounsaturated fats. No wonder EVOO has been linked with many health bonuses, including reducing the risk for cardiovascular disease, improving the management of type 2 diabetes and even breast cancer prevention. (To learn more, see Bottom Line’s article, “The Healthiest Olive Oil.”)

How much is enough? The PREDIMED Study found the most benefits related to consuming 57 grams—about four tablespoons—per day. So that means you can enjoy a little more than a tablespoon per meal drizzled over your foods as your source of additional fat.


So, what’s the best way to cook your vegetables with EVOO? “Start with the real deal—extra-virgin olive oil—which works wonderfully in cooking methods as different as as sautéing, pan-frying, roasting or grilling,” she says. “Don’t fall for the myth that more is better. At 120 calories per tablespoon, EVOO is concentrated stuff. If you dump a quarter cup of it over your salad or pasta, you’re adding an extra 480 calories to your meal, which most people simply can’t afford. If you gain weight, that can quickly erase the potential health benefits from olive oil.” The good news is that you don’t need much olive oil to pump up both the flavor and healthfulness of your favorite vegetables.

When you’re sauteeing vegetables, for example, just heat one or two tablespoons of olive oil in a sauté pan or skillet and then add about four cups of any medley of vegetables. Drizzle a twist of lemon juice and your favorite pinch of spices and herbs, and sauté until just crisp-tender to make about four servings. (For more healthful pan-frying tips, see Bottom Line’s article, “What If Fried Foods Were Healthy?”) One or two tablespoons is also a good amount for four servings when you’re roasting vegetables or making a salad.

What about boiling vegetables in just a little water or steaming them? That’s still nutritious—while it won’t enhance their phenols, it actually retains nutrients such as vitamin C best—and you can make it more phenol-rich by simply tossing your steamed (or even microwaved) vegetables with a little EVOO.

Bottom line: It’s fine to include some veggies sautéed or even fried in olive oil in your diet, but it’s not the only way to get the health benefits of vegetables—or olive oil.