If you’re on social media, you may have seen all the talk about vegetable oil being unhealthy—or even dangerous. Though many experts say vegetable oil can be a part of a healthy and balanced diet, others imply that these oils (also dubbed seed oils) should be avoided.
So, is vegetable oil really something that should be on your do-not-eat list, or can people eat it and still be healthy? We dug into the research to find out so you can know, once and for all, whether vegetable oil is healthy or not.
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What Is Vegetable Oil?
Vegetable oil is an oil that is extracted from certain vegetables, like corn and soybeans. Seed oil is also considered vegetable oil. On the other hand, oils extracted from fruit (like olive and avocado oil) may or may not fall under the vegetable oil classification, depending on a person’s definition of the term.
Canola, soybean, corn, and sunflower oils are all examples of vegetable oil. These oils are liquid at room temperature, and many are typically mild in flavor.
Vegetable oils can be produced in different ways. Refined oils are extracted from their original source using a chemical solvent. Cold-pressed oils are produced by applying pressure to the plant to extract the oil.
These oils are found in a wide variety of recipes like salad dressings, baked goods and certain mayonnaises and marinades.
Vegetable Oil Nutrition
Hearing the word vegetable may conjure thoughts of loads of vitamins, minerals and fiber. But unlike many whole-vegetable options, like spinach and carrots, vegetable oil is not packed with the nutrients you would expect to see in a veggie.
Vegetable oil is a source of fat. In some cases, vegetable oil consists of primarily polyunsaturated fatty acids, or PUFAs. Your body can’t make PUFAs, and according to the American Heart Association, consuming these fats can have heart-health benefits, especially if you use them to replace sources of saturated fat in your diet. Under the PUFA umbrella, there are omega-3 and omega-6 fatty acids. Certain vegetable oils can be quite rich in omega-6 fatty acids, which is an important factor to note. But more on that later.
Vegetable oils can also contain monounsaturated fats, which have also been linked to heart-health benefits.
According to the USDA, 1 tablespoon of soybean oil, a commonly consumed vegetable oil, contains the following nutrients:
- Calories: 120
- Protein: 0 grams
- Fat: 14 grams
- Carbohydrates: 0 grams
- Sugar: 0 grams
- Cholesterol: 0 grams
Some vegetable oils naturally contain plant compounds that may offer health benefits, including phenolic acids and flavonoids, notes 2021 research in Trends in Food Science & Technology. Some vegetable oils have synthetic antioxidants added to them. Natural additives can be added to prolong the shelf life of the oil, according to the Journal of Food Science and Technology in 2020. That’s because the fats in the oil can oxidize when exposed to light or oxygen.
Heating May Impact the Oil’s Nutrition
Vegetable oils are a go-to for many recipes that require a fat source to achieve a high heat, like fried foods. But once some of these oils are heated, certain compounds can be formed, which is where there may be a reason to be concerned.
For the oils that contain large amounts of an omega-6 fatty acid called linoleic acid (think rapeseed, soybean and sunflower), heating them to a certain temperature forms a compound called hydroxynonenal, points out research in Advances in Nutrition in 2020. Typically, this happens when the oils are heated beyond their smoke point. Once they’re eaten, the compounds may promote disease, the authors point out.
How the Oil Is Processed May Impact Its Nutrition
One way to make vegetable oil relies on hexane, a compound found in many products, such as cleaning agents and stain removers. Hexane is used to extract the oil from the plant. Inhaling high levels of hexane can cause dizziness, nausea and headaches; long-term exposure can cause muscle weakness, blurred vision, fatigue and headaches, according to the Environmental Protection Agency. That all certainly sounds unsettling. And even small, or trace, amounts of hexane left over after processing can add up if you’re consuming multiple sources of it, a study in Foods in 2022 notes.
The European Union has suggested a a residue limit of no more than 1 milligram of hexane per kilogram of food. A 2017 study in the Journal of Experimental and Clinical Toxicology analyzed the hexane content of various oils, including sunflower, corn and canola. Researchers found that all of the 40 oils studied contained hexane levels that were lower than the EU maximum residue limit.
How Omega-3 and Omega-6 Fatty Acid Ratios Impact Health
Omega-3 and omega-6 fatty acids are PUFAs, and both types of omegas are important for supporting our overall health. However, consuming large quantities of omega-6 fatty acids while simultaneously eating low amounts of omega-3 fatty acids may not be good for your health. Since some varieties of vegetable oils are rich in omega-6 fatty acids, this is a factor that is worth noting.
A diet rich in omega-6s but low in omega-3s may increase inflammation, while a diet that includes similar amounts of each type of fatty acid may reduce inflammation. Vegetable oils with higher proportions of omega-6 fatty acids include sunflower, corn and soybean, according to 2020 research in Advances in Nutrition. Omega-6 fatty acids don’t necessarily need to be avoided, but they should be balanced out with enough omega-3s in your overall diet to help even the ratio of fatty acids.
In short, if you consume vegetable oils, it may be healthiest to also eat sources of omega-3 fatty acids, such as oily fish, walnuts and avocados.
The Bottom Line
Depending on who you get your nutrition info from, vegetable oils are either considered a positive addition to your healthy diet or one of the worst things you can eat. Very confusing.
According to research from the American Heart Association, consuming vegetable oils is linked to positive health outcomes like a reduced risk of stroke. It’s important to remember that how much oil you eat matters. Including small quantities of vegetable oils in an otherwise-healthy diet (especially when these oils replace saturated fats) can be perfectly fine.
For the best way to include vegetable oils in your diet, remember to avoid heating vegetable oils beyond their smoke point and also to eat foods that are rich in omega-3 fatty acids. Go ahead, feel free to enjoy a flavorful Caraway Vinaigrette, both of which are made with vegetable oil, knowing that—despite what Dr. Google will have you believe—your overall health will be just fine.