If you’re a fan of fried foods, recent reports of a new study on the benefits of frying your vegetables — versus boiling them — might have had you rubbing your eyes in disbelief.
The study from researchers in Spain and Mexico measured the fat, phenol, and antioxidant content of certain vegetables common in the Mediterranean diet when they were sautéed in extra virgin olive oil, or boiled in water or in a water/oil mixture. The veggies in question: tomatoes, potatoes, pumpkin, and eggplants.
They found that sautéing the vegetables in extra virgin olive oil enriched them with natural phenols, a type of antioxidant linked to prevention of cancer, diabetes, and macular degeneration. This was mainly attributed to the olive oil itself, which “enriched” the vegetables with its own phenols.
Boiling vegetables, meanwhile, merely conserved their already existing antioxidant capacity.
So Are Fried Vegetables Now Good for You?
Nutrition science has advised against fried foods for decades, consistently pointing out that many of the oils commonly used for frying can raise blood cholesterol and clog arteries, and all can add to your waistline.
Despite all of the misleading headlines, the new study does not change any of that. That’s not even what the researchers sought to prove.
Researchers wanted to understand if nutrients — notably, phenols — were added, lost, or enhanced in each of the cooking methods. We don’t talk much about phenols, but they are important nutrients. They are naturally occurring antioxidants unique to many vegetables. They contribute to the vegetables’ flavor and can be supportive of good health. For example, the phenol thymol, found in thyme, has antiseptic properties. Capsaicin, found in chilies and peppers, can be used for pain relief. Phenols have also been studied for their anti-cancer properties.
The study showed that foods sautéed in olive oil had phenols that weren’t present in the raw form — because they picked up phenols from the olive oil in deep-frying and sautéing, and thus the antioxidant capacity of the foods increased when they were prepared in oil.
The study itself is not terribly confusing, just limited in its reach. However, many of the stories published about the study have misled readers into thinking frying is good.
"I worry about how this information is communicated,” says Las Vegas-based dietician Andy Bellatti, M.S., R.D. First, he notes, the study covers only four vegetables — potatoes, tomatoes, eggplant, and pumpkin. While the first two are fixtures of the average American diet, the four together in no way comprise the entire category of “vegetables,” in which most of us would include many green vegetables such as lettuces and broccoli.
Second, most reports fail to distinguish between “frying” and “sautéing.” These are not interchangeable terms.
“Frying is a method where the vegetable is cooked by submerging it in oil,” notes Toby Amidor, M.S., R.D., nutrition expert and author of “The Greek Yogurt Kitchen.” By contrast, sautéing means cooking in a small amount of oil. It also usually implies cooking quickly, resulting in a lightly cooked food. Frying can take much longer, allowing the food to absorb more fat. Also, deep-frying often implies a higher cooking temperature, which is not good with extra virgin olive oil, as this oil has a low smoke point.
What the Study Doesn’t Cover
Notably absent from the study — and most reports covering it — is the cooking method generally understood to be the healthiest for most vegetables: steaming.
Previous studies show that steaming (and boiling) vegetables help to soften and break them down, making their nutrients easier to digest than when they are raw. And studies that have focused on other vegetables — like carrots, courgettes (zucchini), and broccoli — actually found that frying them caused them to retain less nutrients and antioxidants than boiling or steaming.
The new study also notes that, while sautéed vegetables had boosted antioxidant capacity, the olive oil also added unwanted and unnecessary fats, boosting their calorie content in the process.
While it’s helpful to keep up with the latest health news, don’t let one study change dietary habits that are working for you.
If you currently steam your vegetables, there’s no reason to change that. If you prefer them fried, try sautéing them instead. While the 2015 USDA Dietary Guidelines do not limit the amount of healthy fats like olive oil, such fats are not necessary to get the most out of cooked vegetables. “Eating some type of fat with vegetables is important for maximum nutrients and antioxidant absorption,” says Bellatti. “But this can also be achieved by eating a meal that includes raw or steamed vegetables along with healthy fats like avocados, nuts, and seeds.”
“The key to health is to eat plenty of plant-based foods — that much we know. Overall, I recommend people focus more on eating at least 2 1/2 cups of vegetables every day — ideally, ones of various colors, and a combination of both raw and cooked.”