Facts Behind Our Fats: The Truth About Seed Oils
- Piece of Cake Staff
- 3 hours ago
- 10 min read
Written by Lindsay Grohs
If you’re on the same side of Instagram and TikTok as I am (aka the foodie feed), you’ve probably seen the recent uproar over seed oils. Debates on their toxicity. Warnings about their health risks. Questions about whether or not we should even be consuming them at all. These conversations are all over social media lately. As someone who is just as curious as many of you are, I wanted to dive deeper into the world of seed oils. In this article, we’ll break down what seed oils are and how they’re made, debunk myths, and reveal truths, shedding light on the real health concerns worth paying attention to.
What are Seed Oils
Seed oils are exactly what they sound like: oils extracted from the seed of a plant. Some common ones include sunflower oil, soybean oil, canola oil, and grapeseed oil, to name a few. These oils first emerged in the early 1900s in attempts to lower the costs of oils and allow for mass production. Cottonseed oil was the first to make headlines as soapmakers William Proctor and James Gamble began creating soap from this vegetable oil. Before Proctor and Gamble adopted cottonseed oil in their soapmaking process, cottonseed oil was “consigned to the status of “toxic waste,” (Kresser, 2019). Once the process of “hydrogenation”-- where oil could be chemically altered and turned into solid cooking fat—was discovered, the “toxic waste” label went out the window. The industry was focused on efficiency and mass production. More seed oils emerged after this, quickly becoming popular with their cheap prices and versatile uses in home cooking, fried foods, and processed and ultra-processed foods.
Production Process
To put it simply, the process of producing seed oils entails bleaching, refining, and heating the seeds to produce an oil out of them. The seeds are first gathered and heated to high temperatures, oxidizing the unsaturated fatty acids within the seeds in the process. These unsaturated fats—like omega-3 fatty acids—support heart health, which is one reason why seeds themselves are considered a nutritious addition to the diet. Oxidizing these unsaturated fatty acids turns these fats into unstable compounds, creating toxic byproducts such as hydroperoxides and aldehydes. Hydroperoxides, the primary byproducts produced, “were reported to be toxic to the human body because of their possible inhibition of the enzymes” (Xu, Høy, & Adler-Nissen, 1998). Enzymes are essential proteins that help your body perform basic biological functions. When these enzymes are inhibited, it can interfere with bodily functions—disrupting digestion, metabolism, detoxification, and immune function. Aldehydes are toxic chemicals that, when consumed, can impair cellular functions and damage proteins and DNA. Aldehydes have also been linked to diseases such as various cancers and cardiovascular disease.
The second step in the seed oil production process, which is equally as toxic and harmful, is processing the seeds with a petroleum-based solvent “to maximize the amount of oil extracted from them” (Kresser, 2019). A common solvent used for this process is hexane. Hexane is harmful to both humans and animals, causing short- and long-term effects on the nervous system and respiratory system, as well as the skin and eyes. Studies have shown “altered neurological function in humans exposed to n-hexane, commonly referred to as peripheral neuropathy” (Agency for Toxic Substances and Disease Registry, 2025). These effects include muscle weakness, numbness, decreased sensation, alterations in nerve conduction, longer menstrual cycles, pregnancy complications, and more.
The next step is deodorizing the oils to make them smell better—but at what cost? This process not only produces trans fats, which are harmful to the body, but also “destroys or removes the beneficial components from oils and leads to the decrease of ALA and carbonyl compound formation” (Kong et al., 2024). Trans fats can raise low-density (LDL) cholesterol (“bad cholesterol”) and lower high-density (HDL) cholesterol (“good cholesterol”), causing a greater risk of heart attacks and strokes (Mayo Clinic Staff, 2025). ALA (alpha-linolenic acid) is one of three major plant-based omega-3 fatty acids—essential fats that can only be obtained through diet. ALAs contribute to cardiovascular health, bone health, and chronic disease prevention (Rajaram, 2014). When ALA levels are decreased during oil processing, these health benefits may be significantly reduced.
The final step in seed oil production is...adding more chemicals. This stage is when synthetic antioxidants, colorants, and preservatives are added to improve color, shelf life, and/or texture, all of which further distance the oil from its natural origin. These synthetic antioxidants include compounds such as BHT (butylated hydroxytoluene), BHA (butylated hydroxyanisole), and TBHQ (tertiary-butylhydroquinone)—all of which contribute to hormone disruption and carcinogenic (cancer-causing) effects (Xu et al., 2021).
Nutritional Profile
Now that you have a solid overview of how seed oils are produced—and are familiar with the byproducts created and chemicals added along the way—let’s fill in a few of the remaining blanks. We already know from the section above that seed oils contain toxic byproducts like hydroperoxides and aldehydes, hexane (a toxic petroleum-based solvent), synthetic antioxidants such as BHT, BHA, and TBHQ, and in many cases, they can even produce trans fats during the process. Seed oils are also very high in omega-6 fatty acids, a type of polyunsaturated fat (PUFA). While your body needs a small amount of these fats to function, the amount of PUFAs in seed oils is well over what we should be consuming. Sunflower oil, like many other seed oils, “contains approximately 65-70% omega-6 linoleic acid” (Nelson, 2023). These fats affect our cells. So much so “that as the fat composition of the Western diet has shifted, so too has the fat composition of our cells,” leading to a “2.5-fold increase in linoleic acid content (the omega-6 that's abundant in seed oils) from 1959 to 2008” (Zeidman, 2022). In addition to omega-6 fatty acids contributing to cell composition shifts, they also can cause chronic inflammation and oxidative stress. Oxidative stress is “when there is an imbalance between your body's production of free radicals and the antioxidant compounds needed to combat them,” resulting in further cellular damage and, once again, toxic byproducts linked to various chronic diseases (Ziedman, 2022).
Health Issues
Now that we’ve unpacked the chemical processing and broken down the nutritional profile, it’s time to dive into what really matters: how seed oils may be impacting our health. While we’ve touched on some of these concerns earlier, this section will break it all down clearly and thoroughly.
One of the most talked-about concerns is chronic inflammation. When consumed in excess, the high levels of omega-6 fatty acids found in seed oils can disrupt the delicate balance between omega-6 and omega-3 fats in the body. This imbalance leads to chronic inflammation, heart disease, autoimmune conditions, macular degeneration (eye disease), diabetes, obesity, and more (Kresser, 2019). Another major concern is oxidative stress. As mentioned earlier, this occurs when the body is overwhelmed by free radicals—unstable molecules that can damage cells. The byproducts formed during high-heat seed oil processing (like hydroperoxides and aldehydes) are known to generate these free radicals. Over time, this can lead to cellular damage and increased risk of chronic diseases such as Alzheimer's, heart disease, and liver disease.
And then there’s hormonal disruption. Additives like BHA, BHT, and TBHQ—used to preserve shelf life—interfere with hormone signaling. “The European Union classifies BHA as a suspected endocrine-disrupting compound,” raising red flags for fertility, reproductive health, and developmental health for children (Holcombe, 2025). In addition to this, these additives contribute to carcinogenic effects, increasing cancer risks.
Finally, at least for now, there's growing concern over neurological and reproductive effects, especially in connection with compounds like hexane. Long-term exposure to these industrial solvents—whether through food, air, or occupation—has been linked to nerve damage, mood imbalances, irregular menstrual cycles, and increased risks during pregnancy.
Commonly Found In…
Seed oils are harder to spot than you might think. They aren’t just hiding in your bottle of vegetable oil but are rather a common addition to many packaged, processed, and fried foods. They have, unfortunately, become a staple in modern food production due to their low cost and long shelf life. The main ones to avoid include canola (rapeseed) oil, corn oil, cottonseed oil, grapeseed oil, soybean oil, sunflower oil, safflower oil, rice bran oil, and peanut oil—often referred to as the “hateful eight.” These oils show up most frequently under three main umbrellas: packaged foods, fast foods, and restaurant meals. While the full list of packaged items is extensive, seed oils are especially common in snacks, cereals, condiments, frozen meals, crackers, breads, and condiments. They’re also frequently used for deep-frying, making fast food items a common culprit.
Substitutions
No need to panic—I’m not going to hit you with all this unsettling info and leave you hanging. The good news is that there are healthier, more natural alternatives to seed oils that can nourish your body instead of harming it. Some of the best fats to cook with and consume include extra virgin olive oil, coconut oil, avocado oil, butter and ghee, pastured tallow and lard, and duck fat.
Olive oil is rich in healthy monounsaturated fats (MUFAs), antioxidants, and antibacterial properties (Leech, 2024). The key here is to make sure you are buying extra virgin olive oil, as its grade determines the oil’s purity, antioxidant content, and health benefits.
Coconut oil is rich in “medium-chain triglycerides (MCTs), a type of saturated fat,” that has fat-burning, antimicrobial, and antifungal properties (Lang, 2024). These things contribute to weight loss, increased energy, and skin, hair, and oral health. Coconut oil is also a great source of antioxidants, which help reduce harmful free radicals, thus reducing the risk of chronic diseases.
Avocado oil is “rich in oleic acid, polyunsaturated fats, carotenoids, and other antioxidant-rich nutrients that are linked to improved heart, skin, and eye health” (Palsdottir, 2024). One standout nutrient is lutein, an antioxidant found in avocados that’s especially known for supporting eye health. Since lutein can only be obtained through diet, using avocado oil in your cooking, salad dressings, or dips is an easy and nourishing way to boost your intake.
Butter and ghee are also great alternative choices of fat to cook with. The production process of butter is straightforward and simple, as the cream is separated from the milk, then churned “until the milk fat—or butter—clumps together and separates from the liquid portion—or buttermilk” (Arnarson, 2019). Ghee’s production process is similar, as it is clarified butter—butter with water and milk solids removed. It’s made by simply heating up butter, as that removes the water and milk solids from the fat. Butter and ghee contain butyric acid, a short-chain fatty acid linked to “reducing inflammation in the digestive system” (Arnarson, 2019). These fats also contain daily trans fats (aka healthy trans fats) that are associated with cancer-protecting properties and weight regulation. Lastly, butter and ghee are vitamin-rich. Butter contains vitamins A, D, E, B12, and K2. Ghee contains vitamins A, E, and K. It’s important to eat both butter and ghee in moderation, as they are calorically high and may have links to increased weight gain or heart disease when consumed excessively.
Tallow and lard are animal fats that are good natural sources of fat to cook with and consume. Tallow is rendered beef fat, while lard is rendered pork fat. Beef tallow is rich in flavor, making it perfect for meat and vegetable dishes. Lard has a more neutral flavor profile, with a touch of sweetness. These fats are rich in fat-soluble vitamins, containing vitamins A, D, E, and K, as well as various fatty acids. In addition to these nutritional benefits, they also have a longer shelf life, making them an even greater contender as a substitute for seed oils.
Conclusion
While seed oils may have become a convenient staple in the modern food industry, their health implications are far too significant to ignore. From the chemical processing to the toxic byproducts and impacts on chronic inflammation, hormone disruption, neurological and reproductive issues, and long-term disease risk, it’s clear that we need to be more mindful about the oils we consume daily. With so much information (and misinformation) on social media, it can be hard to separate fact from fiction. You now have some general knowledge around seed oils and their health effects. It’s up to you what you do with it! Remember, it doesn’t have to be something radical. Starting with something as simple as changing the fats we use to cook our meals can be so beneficial in the long run. By choosing more natural, nutrient-dense fats like extra virgin olive oil, avocado oil, and grass-fed butter or ghee, we can support our bodies rather than burden them. Small, informed swaps can lead to big changes in how we feel and function every day. So next time you grab an item at the grocery store, take a moment to read the label. Awareness is the first step towards better health!
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