When it comes time to whip up your favorite meal, one of the first items you'll grab is probably some form of vegetable oil or animal fat — like a jug of canola oil or a tub of butter. But have you ever stopped to think about what option is the healthiest way to kickstart a recipe? The choices may seem overwhelming, and now, many consumers are embroiled in a hot debate over growing suspicion of seed oils.
Critics of seed oils have claimed that the ingredients are toxic to the human body, influencing a slew of maladies from heart disease to weight gain. These arguments condemn the processing that the oils go through and tend to prop up animal fats like lard and beef tallow as better alternatives.
What to believe, then? See the full picture of seed oils and how they compare to animal fats in terms of human health.
How Are Seed Oils Processed?
Seed oils come in a variety of forms, but those branded as part of what’s called the “hateful eight” have come under the most scrutiny. This group includes canola, corn, cottonseed, grapeseed, rice bran, soybean, safflower, and sunflower oils.
Skepticism of the hateful eight stems from the production process of many seed oils, which uses mechanical or chemical treatment. Edible oil processing commonly relies on hexane, a solvent used to extract oil from seeds after they’re crushed. Although high concentrations of hexane in its gaseous form can trigger mild nervous system effects (such as headaches and dizziness) through inhalation, the liquid solvent form used to extract oils is evaporated off until there is none left in seed oil, or extremely small trace amounts that don’t have a toxic effect.
Still, there have been calls to switch to alternative solutions like “green solvents” (like water or C02) or “bio-based solvents” (derived from crops) that would allay any safety concerns, on top of being more environmentally friendly.
Another process used by some facilities is cold-pressing, when oil is pressed at a temperature below 49 C (120 F), often without the need for chemical solvents like hexane. This method has also been purported to retain more nutrients and bioactive compounds compared to refined oils.
Read More: Is the Mediterranean Diet Healthy?
The Effects of Omega-6 Fatty Acids
Another claim that seed oil critics bring up relates to its omega-6 fatty acid content. Omega-6 fatty acids are an essential component of diets that lowers “bad” cholesterol levels (LDL) and raises “good” cholesterol levels (HDL), boosting heart health.
Omega-6 fats, taking the form of linoleic acid in seed oils, have been blamed for inciting inflammation. This argument, however, does not tell the full story. It seems more likely that a skewed balance of omega-6 fats and omega-3 fats could be the reason people experience health problems; omega-3 fats, found mostly in fatty fish like salmon and mackerel, are even more essential than their omega-6 counterparts, but most people aren't consuming nearly enough of it. One 2023 review published in Nutrients states that the “standard American diet comprises 14 to 25 times more omega-6 fatty acids than omega-3 fatty acids.”
It may be easy to pin the blame on omega-6 fats, but studies have shown that they have cardiovascular benefits. It appears the problem isn’t that omega-6 fats are pro-inflammatory but rather that omega-3 fats are just noticeably more anti-inflammatory, and humans aren’t getting enough in their diets.
Seed oils are also unfortunately paired with foods that are already ultra-processed, in which refined carbohydrates, sodium, and sugar are more to blame for health problems like weight gain.
Animal Fats vs. Vegetable Oils
Animal products that are high in saturated fats — like butter, lard, and tallow — have been shown to cause adverse health effects. While they do make food delicious, consuming too much poses the risk of heart disease and contributes to obesity. In small amounts, though, they can be safe to add to food.
A 2021 study published in BMC Medicine found that consumption of butter and margarine was associated with higher total mortality, while canola oil and olive oil were linked with lower total mortality. Scientists came to a similar conclusion in a recent study published March 2025 in JAMA Internal Medicine, suggesting that substituting butter with plant-based oils may help prevent premature death.
For those looking to find a healthy solution, olive oil stands out as a valuable choice. It is not a seed oil, and instead comes from the fleshy part of the ripened olive fruit that is pressed without the need for solvents. In addition to lowering LDL cholesterol and improving heart health, it contains key vitamins (like vitamins E and K) and minerals.
Read More: Beef Tallow Probably Isn’t the Skincare Miracle You Hoped it Was
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
American Heart Association. There's no reason to avoid seed oils and plenty of reasons to eat them
Penn State. Processing Edible Oils
The Nutrition Source. Ask the Expert: Concerns about canola oil
PubMed. Green solvents and technologies for oil extraction from oilseeds
PubMed. Editorial: Cold Pressed Oils: A Green Source of Specialty Oils, volume II
Harvard Health Publishing. No need to avoid healthy omega-6 fats
Stanford Medicine. 5 things to know about the effects of seed oils on health
PubMed. Cooking oil/fat consumption and deaths from cardiometabolic diseases and other causes: prospective analysis of 521,120 individuals
Jack Knudson is an assistant editor at Discover with a strong interest in environmental science and history. Before joining Discover in 2023, he studied journalism at the Scripps College of Communication at Ohio University and previously interned at Recycling Today magazine.
