Are Seed Oils Bad For Your Health?

Here's what you need to know.

Published September 25, 2023

Yellow oil being poured into a container

Kristian Septimius Krogh/Getty Images

Although we shouldn’t believe everything on the internet, it’s hard to ignore social media warnings that seed oils are toxic.

But “seed oils are not the bad guys they’ve been made out to be,” reported C.J. Trent-Gurbuz, senior health editor, in U.S. News & World Report.

And claims that seed oils cause inflammation aren’t backed by current research.

Canola, corn, cottonseed, grape-seed, rice bran, sunflower, safflower and soybean oils are pressed from seeds. Seed oils are neutral in flavor and are commonly used in cooking, but the real concern is that they’re prevalent in processed foods (cookies, salad dressings, crackers, shortening, mayonnaise), french fries and candy.

My grandmother baked with butter, and my mother switched to margarine; both lived to their mid-90s. Many of us jumped on the olive oil bandwagon when the American Heart Association cited research that found a 15 percent lower risk of cardiovascular disease if you consumed more than half a tablespoon of olive oil daily. Yet vegetable oils are often purified, refined, even chemically altered, which is why many consumers have gravitated toward oils extracted from crushed seeds.

The facts about oil fats

Before you decide which kinds of oils to use, understand how unsaturated fats — which look liquid in nature and are predominantly found in foods from plants — differ. They break down into two categories.

· Monounsaturated: olive, peanut and canola oils.

· Polyunsaturated: sunflower, corn, soybean and flaxseed oils.

Seed oils are high in polyunsaturated fats and omega-6 fatty acids, and some are a good source of vitamin E. Research reported by Harvard Health suggests that a diet high in omega-6 fatty acids can help lower cholesterol and blood sugar, and reduce heart disease risk.

Omega-6 fatty acids are essential for our health, but our bodies cannot produce them; we need to ingest them from foods. The Harvard T.H. Chan School of Public Health recommends that 5 to 10 percent of our daily calories should come from polyunsaturated fats, while saturated fats — found in large amounts in cheese, milk, butter, meat and fast food; coconut oil contains about 90 percent saturated fat — should be limited to 5 to 6 percent of our daily intake.

Seed oils contain both omega-3 and omega-6 fatty acids. Chemicals such as hexane can be used in processing seed oils, but the safest options are cold-pressed — also known as expeller-pressed — oils, extracted without heat. Although cold-pressed oils are higher in nutrients, they spoil more quickly; purchase smaller quantities, and store them in a dark-colored bottle in a cabinet or the refrigerator.

Cooking with seed oils

“When you bring unsaturated fats repeatedly to high temperatures, you’ll get a buildup of damaging chemicals,” said Guy Crosby, adjunct associate professor of nutrition at the Harvard Chan School. Crosby, however, quoted in a Consumer Reports article, argued against the idea that these oils cause headaches, heart disease and other health issues.

“Cooking with seed oils at home isn’t an issue,” he claimed. Some sources recommend never reusing seed oils in cooking. If any oil smells rancid, toss it.

The benefits of seed oils

Seed oils are rich in unsaturated fats, which don’t clog arteries like saturated fats. Seed oils’ healthy fats can lower blood cholesterol and are less inflammatory than other fats. Limit fried and ultra-processed foods. Aside from their high oil content, they are high in carbohydrates, sugar and salt.

Avoid hydrogenated and partially hydrogenated oils. Cold-pressed oils, made without heat or chemicals, are better options. Although they tend to be pricier, they contain more nutrients and antioxidants.

And make your own salad dressings. The ingredients are all in your pantry: oil, vinegar or lemon juice, mustard, sea salt, pepper, garlic or herbs. This way you’re in control of selecting the healthiest oil.

Also, health-conscious consumers should always read food labels carefully.

What kind of oil do you typically use? Let us know in the comments below.

Candy Schulman’s essays, health, and travel pieces have appeared in AARP, The New York Times, The Washington Post, Next Avenue, Oldster, Parents, Travel & Leisure, among others. She is a creative writing professor at the New School in New York City and a private writing coach. Learn more at www.candyschulman.com.