6 Health Myths About Oils

August 15, 2024 12:00 PM EDT

Online health influencers have plenty to say lately about oils. We should cook with certain oils, banish others from our pantries, swish them around our mouths for flawless gumlines, and lather our bodies and hair with them for everlasting beauty. About the only purposes not suggested for oils are finding lost socks and doing our taxes.

The focus on oils isn’t exactly new; they’ve been praised and debated for eons. The difference today is that scientific research can help separate fact from fiction. But studies are often misunderstood or rejected in favor of personal anecdotes that may be unreliable.

Here are the biggest oil myths going around the internet, according to scientists.

Myth #1: It’s bad to cook with olive oil

The unrefined version of olive oil—extra virgin, or EVOO—provides significant health benefits, especially in preventing heart disease. However, some online gurus say cooking with EVOO is problematic because of its low smoke point, meaning that, when heated, it may start smoking sooner than other oils. The smoke is viewed as a signal of chemicals developing in food that may eventually cause cancer and heart disease.

But scientific research doesn’t support this “where there’s smoke, there’s fire” theory. In fact, cooking with EVOO can make both the oil and the food it’s covering healthier, compared to the same food eaten raw, according to recent research.

Smoke “doesn’t correlate very well with the actual breakdown of the oil,” says Selina Wang, associate professor of food science and technology at University of California, Davis. EVOO is packed with phenols, compounds that support health partly by reducing inflammation. Phenols also protect the oil from deteriorating—regardless of whether it’s smoking. Unlike other oils, “EVOO has the ability to protect itself,” Wang says.

Oils produce the most smoke during high-temperature cooking processes like frying, which aren’t healthy to begin with. “Smoke point is irrelevant because we shouldn’t cook at those temperatures,” says Mary Flynn, associate professor of medicine at Brown University who studies olive oil.

Wang advises cooking food like vegetables in EVOO at lower temperatures, below 400°F, for just long enough to heat up the veggies—and for their health-giving properties to seep into the oil’s healthy fat. (On a stovetop, this advice may translate to medium heat, though stoves vary in their cooking strengths.) Once transferred to the oil, the beneficial components, such as vitamins and substances called antioxidants that protect the cells from unstable molecules, are absorbed better by our bodies. Antioxidants called carotenoids, for example, help protect against cancer.

The synergy goes the other way, too: the healthy olive oil components “get sucked into the vegetables,” Flynn says. “In the U.S., we don’t consume our vegetables with fat.” That’s a mistake, because when it comes to getting these micronutrients, “if you’re not cooking vegetables with fat, they’re not getting into your body.”

Reducing cooking times with EVOO will also ensure a high level of phenols. If cooked longer, their levels decline. Diets rich in phenols are linked to lower risk of heart disease, cancer, and neurodegenerative diseases.

Myth #2: More expensive oil is healthier

The prices of cooking oils are sometimes inflated to suggest they’re superior to their shelf neighbors. In reality, the cost of EVOO reveals little about its quality. Often, bottles between $45 and $90 are “no better” than more reasonably-priced brands.

Instead of cost, judge EVOO by whether the bottle was produced in California. Large producers in California must pass the state’s tests requiring purity and authenticity. Olive oil is often fraudulent and mixed with other cheaper oils.

Freshness matters, too. Look for bottles with “harvest dates” showing they’re relatively new to shelves. After opening a bottle, try to use it within four to six weeks. Secure the cap tightly between uses. “Oxygen will destroy the health components,” explains Flynn, who is also an independent science advisor to the Olive Wellness Institute.

Most important may be an old-fashioned taste test. “One of the best tools we can give consumers is to know the flavor of good olive oil,” Wang says. A teaspoon of EVOO should taste slightly bitter at first, she says, followed by a pungent, spicy tingle at the back of your throat—a sign of its phenols—perhaps causing a couple of coughs.

Myth #3: Non-olive oils are unhealthy

Seed oils such as canola are the scourge of several online influencers, who cite studies on the harms of consuming these oils. But such studies are often misinterpreted. Scientists think seed and vegetable oils can be healthy, with some important caveats.

Unlike EVOO, most oils are refined, meaning they’re heat-treated. This process strips some of their healthful properties—reducing their phenols, for example. However, refined oils like canola are still high in monounsaturated fats—though not as high as EVOO—that buoy heart health.

“I don’t want to stigmatize other oils,” Wang says, because they’re generally more affordable than EVOO. She has friends who understand EVOO’s benefits but buy less expensive seed and vegetable oils to save money.

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These oils are healthy enough for home cooking, but the problem is what happens in restaurant kitchens, Wang says. Trying to keep their costs low, many restaurants cook with cheap oils like canola and reuse the same oil puddle. Over several hours, the fats in these recycled oils become oxidized, producing harmful compounds that can lead to serious health issues for those who dine out often. The same concern applies to many cooked items in the prepared food sections of supermarkets.

Like technology, Wang says, it’s not seed or vegetable oils themselves that are bad, but how they’re made and used.

In theory, avocado oil is another healthy option, but the vast majority of brands are rancid or mixed with less healthy oils, Wang has found.

Coconut oil, on the other hand, is inherently unhealthy, says Qi Sun, an associate professor of nutrition at Harvard, despite influencers touting the benefits of consuming it, such as curing back pain and boosting energy and cognition. Scant research supports these claims, and coconut oil is high in unhealthy saturated fats; one tablespoon-sized serving has about 90% of the daily allowance recommended by the American Heart Association. Because it raises fats in the blood linked to heart disease—LDL cholesterol and triglycerides—“you can conclude it wouldn’t provide any cardiovascular benefits,” Sun says. “It’s not too different from butter or lard.”

By comparison, the same amount of olive oil has 15% of daily recommended saturated fat. Even this lower saturated fat content is potentially harmful, so limit EVOO to 2-4 tablespoons per day, Wang says.

Myth #4: Oil pulling beats brushing and flossing

Another coconut oil myth is that swishing it around the mouth is better for oral health than standard dental practices. Advocates of “oil pulling” claim that the lauric acid in coconut oil helps fight harmful bacteria and plaque that would otherwise build up in the mouth. But credible research hasn’t suggested benefits, whereas brushing and flossing are backed by far more evidence.

“Has oil pulling ever reversed periodontitis or gingivitis? The answer is no,” says Mark Wolff, professor of restorative dentistry at the University of Pennsylvania.

Not that oil pulling will necessarily hurt you. “There’s no real reason it would cause harm,” Wolff says, unless it’s substituted for the gold-standard approaches to oral health. “If you want to oil pull, it’s okay, but still brush and floss,” and use doctor-prescribed antibiotics, not oils, to treat oral infections, says Matthew Messina, assistant professor of dentistry at Ohio State University.

The swishing action of oil pulling may remove debris from between teeth, which could help with preventing dental problems. But flossing, oral irrigation devices like water flossers, and common mouthwashes with specific antimicrobial ingredients are research-supported options for dislodging these food particles. Sesame and sunflower oils are sometimes recommended for oil pulling, based on Ayurvedic medicine practices. However, like coconut oil, they’re lacking in evidence.

Myth #5: Coconut oil transforms hair

Several oils, including coconut oil, contain fatty acid ingredients that hydrate the hair, softening and smoothing it. But claims about the wonders of suffusing hair with coconut oil are exaggerated. These oils may cause more harm than benefit, depending on the person.

Coconut oil could help some who regularly color their hair, heat it, or use potentially harmful products, says Dr. Joshua Zeichner, associate professor of dermatology at Mt. Sinai Hospital in New York City. “You want to make sure you’re hydrating the hair shaft, strengthening and protecting it, especially when caring for chemically treated hair,” he says. Coconut oil could serve this purpose by forming a protective barrier. Zeichner compares it to spackling your walls. “It’s kind of filling in the cracks.”

But use it in moderation, says Dr. Michele Green, a New York City dermatologist—not every night.

For dandruff relief, coconut oil is a “double-edged sword,” Zeichner says. “If it creates a greasy environment, it encourages yeast to grow,” worsening dandruff in some cases, he explains.

Don’t reach for EVOO as an alternative, Green says. “There’s no evidence that olive oil improves hair health.” Rosemary oil is a hot trend currently for hair growth, she adds; people massage it into the scalp twice daily, in the morning and evening, leaving it in their hair overnight. “There’s a small research literature showing it could work,” although it can irritate the scalp if it’s not mixed with another oil, like argan or coconut, Green adds.

Myth #6: Oils cure acne

Applying oil to the skin, like the hair, may benefit some people while causing trouble for others.

The lauric acid in coconut oil has antimicrobial properties, “so it's thought to decrease levels of acne-causing bacteria and even yeast on the skin,” Zeichner says. However, coconut oil is comedogenic, meaning it can clog the pores and increase acne. Also comedogenic are olive, marula, flaxseed, and carrot seed oils. “I would stick with refined, non-comedogenic moisturizers proven not to block the pores,” Zeichner says. “The perception is that natural is better, but that’s not always the case.”

Green sees value in natural oils for overall skin health for some patients, but they should be used in moderation and combined with moisturizers. “The additional moisture is retained by the barrier the oils offer,” she says.

EVOO, in particular, may enhance the skin’s natural moisture barrier, due to its healthy fat, antioxidants, and vitamins A, D, K, and E, according to Green. Jojoba, argan, and almond oils could be beneficial, too. Almond oil is a common allergen, though. Test it on one spot to check for irritation, Green suggests.

“Some data from lab studies support the use of individual natural oils on the hair and skin,” Zeichner says. “But we’re lacking studies on the real-world use of products.”