Even other oil companies are chiming in on the discourse. Zero Acre, a company that creates cooking oil from fermented sugarcane, has an entire blog dedicated to cutting down seed oils. Graza, an Instagram-popular olive oil producer, has a chart on the bottom of their website calling canola oil the “petroleum of cooking oils.” Inflammatory, indeed. Between marketing initiatives, social media explainers, and subreddits, seed oils have become the new love-to-hate wellness trend on the internet. It all begs the questions: What *is* a seed oil, and are seed oils actually bad for you?
What oils are seed oils?
Seed oils are oils that are pressed from plant seeds, and are sometimes called vegetable oils. Commonly seen in cooking: Peanut, sunflower, grapeseed, soybean, and corn oils are some of the more prevalent ones on grocery store shelves, and in our food products. So, grapeseed oil comes from the seed of the grapes (a bi-product of winemaking), corn oil comes from the germ—or grain seed—of the corn plant, soybean oil comes from the seed of the soybean plant… you get the point.
One of the most well-known vegetable oils, canola, or rapeseed oil—cultivated in the 1970s—was created using a blend of these different plant and seed oils to create a low-acid oil. The Brassica plant—in the same family as cabbage, broccoli, and more—is the species of plant that food scientists worked with to germinate and create plants that produced the right kind of seed to create canola oil.
Olive oil, though considered a vegetable oil, is not a seed oil. Olives are pressed to extract the oil, and though sometimes pits are included in this pressing, the ratio of olive meat to pits is larger.
Where are seed oils found in our foods?
There’s a pretty long list of foods and food products that have some amount of seed oil in them. Sauces, like mayonnaise, ketchup, and dressings, often use seed oils as emulsifiers. Essentially, the fat of the oil is what keeps the sauce homogenous and not separated, on top of adding delicious flavor and creamy texture. Chips and other snack products are fried in some combination of seed oil. Basically, anything that has a fair amount of fat content will most likely have some sort of seed oil, because it’s more shelf stable than something like butter, which needs refrigeration to extend shelf life.
The most common fatty acid in canola oil is erucic—an omega-9 fatty acid. This monounsaturated (liquid at room temperature and solid when chilled) fatty acid is also found in the seeds of mustard plants, along with some nuts and fish. Erucic acid is considered a non-essential (which just means our body helpfully produces it on its own and doesn’t need us to eat any more of it to get the required daily value), but has been found to reduce insulin resistance in people with type-1 diabetes, and lower ‘bad’ (LDL) cholesterol levels. Avocados (and avocado oil) also have omega-9 fatty acids.
Another fatty acid, polyunsaturated, or omega-6, is found in sunflower, soybean, and grapeseed oils. Omega-6s are essential fatty acids, so our bodies don’t naturally produce them, but they are crucial for things like brain function, growth and development in children, and can even help lower LDL cholesterol. Omega-6 fatty acids are also found in cashews and walnuts.
What are the claims against seed oils?
When we see seed oils in food, it’s usually in the delivery that comes off as scary—calorie-rich, very processed, fried—but the oils themselves have little to do with this. But, because the bulk of consumption comes from foods like doughnuts, chips, candy bars, sugary cereal, etc (things we’d consider in moderation), they get a blanket statement of “bad for you.”
But, as Emily Schultz, a food and beverage Brand Manager points out, food isn’t just simply a fuel source. “There’s cultural significance in every food we eat, tool we use, and way [we] prepare an ingredient,” she says. “Speaking about food from solely the purpose of nutrition and stripping the food from any context about where you’re eating something and why does nothing to move the conversation forward.”
Many broad claims are made around seed oils. But, the science points to seed oils not causing negative health effects in a balanced diet.
- They contain a lot of omega-6 fatty acids. This is true—but it’s not a bad thing! Omega-3s, typically touted as *the* omega fatty acid to include in your diet to help reduce instances of cardiovascular disease and other heart events, have a higher improvement percentage, but omega-6, also found in some of the same foods, like fish, have this same benefit, just on a slightly smaller scale. The American Heart Association even supports adding omega-6 fatty acids to your diet.
- Seed oils have a lot of trans fats. According to a 2015 study, oils like rapeseed, soybean, and sesame did not have detectable amounts of trans fat. In fact, it was even found that baking and frying—two of the biggest “bad” food preparations pointed to—did not change the composition of the oils enough to increase the amount of trans fats. Most trans fats that are in the American diet these days come from dairy and some meat products.
- Every oil that is refined—or processed to improve quality and extend shelf life by removing impurities—is bad. If you repeatedly heat oils to high temperatures, and then reuse that oil over and over, toxic compounds *can* build up. However, that’s not what refining is. By going through a refining process, seed oils are extracted, and gently heated to remove impurities, all while keeping temperatures under 200°F (176°F to be precise). If you’re worried about the heating component of this, we routinely cook chicken to at LEAST 165°F, which is its safe, cooked-through temperature, as cited by the U.S. Department of Agriculture (USDA).
- The solvent used to extract lots of seed oils—hexane—is bad for us. When extracting seed oils—or, after grinding and pressing the seeds, when producers need a way to separate the mass from the oils they’ve released—a solvent is added to the mix and left to evaporate off, which hexane will do. In fact, it’s incredibly easily evaporated, as a statement from the Agency for Toxic Substances and Disease Registry states “If n-hexane is spilled on the ground, much of it will evaporate into the air before it penetrates the soil.” It also has a boiling point of around 156°F, so when the second part of the process, purification, happens, any leftover hexane will cook off when the oil is heated.The danger of hexane to the human body is when its fumes are inhaled, which is why it’s a bad idea to sniff glue or gasoline, which both contain those hexane compounds that evaporate super easily. In food, products that are processed with hexane do not contain any detectable amounts of it, according to a study from 2013.
- It causes inflammation in your body when you consume it. Charissa Lim, a registered dietician and nutrition coach, calls this the biggest myth.“It certainly makes a compelling narrative,” says Lim, “but they ignore a critical component of toxicology by failing to mention where the minimal and maximum effective dosages of seed oils are and instead frame it like smoking a cigarette where even a single drop will immediately ruin the body.”
There are no current randomized control trials involving humans that show seed oils are worse for the human body compared to something like saturated fat. Essentially, linoleic acid, another omega-6 fatty acid in seed oils can convert into arachidonic acid (AA)—a building block for inflammatory compounds. But, it’s only proven to cause inflammation in mice-based studies, and AA doesn’t metabolize or react the same way in the human body.
Are other oils “fresher” than seed oil?
There’s no such thing as “fresh” oil. Or, better said, if any oil is purchased in a store within its “Sell By” date, it is perfectly usable. Though certainly, like any pantry product, there’s a shelf life, no science backs up that an oil within its “Best By” date is better at any point in its shelf life. As a food brand manager, Schultz sees a lot of this in advertising. Companies use “a lot of assumption-based copy…comparing them to ‘expensive’ olive oil, they’re using generalized language that’s not even saying anything,” says Schultz.
She also adds that there is no industry standard marker of “fresh” and the addition of this kind of language is just fluff meant to confuse and redirect consumers to the product being sold. “If it really is SO bad for you, they should be able to source medical studies really easily in these product pages,” she says.
Should you avoid seed oils?
No! “A 2020 systematic review found that higher linoleic acid intake was linked to a modest reduction in overall mortality, including from heart disease and cancer,” says Lim. “This evidence suggests that, rather than causing harm or inflammation, polyunsaturated fats like those in seed oils may actually offer long-term health benefits.”
With any food, it’s all about moderation. Anything in large quantities isn’t going to be great for us, even the good stuff. There are even studies that show stressing about your diet is worse for your long-term health than just enjoying what you like to enjoy, knowing that you’re probably eating a balanced diet alongside it. That’s all to say, you can take that random TikTok nutrition advice with a drop of oil.
