# Are Seed Oils Toxic? The Latest Research Suggests Yes May 15, 2022 **WRITTEN BY:** Corey Nelson ## Article at a Glance - Industrial seed oils were invented when there was no meaningful health regulation, then became increasingly popular based on flawed research suggesting they were heart healthy. - In the intervening 100+ years, numerous _in vitro_ cell studies, animal studies, human clinical trials, and observational studies have demonstrated the toxic effects of seed oils and their byproducts created during heating. - While there are a few possible benefits to seed oils, such as vitamin E, low amounts of omega-3 ALA, and reduction in cholesterol according to some studies, these properties aren't unique to seed oils and don't outweigh the potential for harm. - Industrial seed oils are hard to avoid if you mainly eat food from restaurants and pre-packaged processed foods, but easy to avoid if you learn to read labels and do as much of your cooking as possible. ## Introduction Industrial seed oils, also known as vegetable oils, are in nearly everything. If you use common cooking oils, eat pre-packaged foods, or dine out at most restaurants, you’re probably eating them every day. And you wouldn’t be alone — globally, vegetable oil production has increased more than 16-fold since 1909, has doubled in the last 20 years, and is expected to grow 30% in the next four years. In the United States, the consumption of soybean oil alone has grown 1,000-fold since 1909. Perhaps it’s not a coincidence that increased vegetable oil consumption correlates with higher rates of [obesity](/content/white-papers/how-vegetable-oil-makes-us-fat/index.html), [heart disease](/content/white-papers/seed-oils-as-a-driver-of-heart-disease/index.html), cancer, diabetes, and other modern health problems. With so much evidence pointing to the harmful effects of seed oils, many have described them as “toxic.” But do seed oils meet the definition of toxicity? ## Seed Oils vs. Vegetable Oils: What Are They? The terms “vegetable oil” and “seed oil” are often used interchangeably but actually have different meanings. To explore what the best evidence says about seed oils' safety and possible toxicity, we'll need to start by defining each term. _Vegetable oils_ are any [oils or fats](/content/blog/healthy-oils-fat/index.html) derived from crops, including fruits, grains, nuts, and seeds. This is a broad category that includes all crop-based oils. Seed oils, also called _industrial_ seed oils, are a particular category of vegetable oils that are derived from seeds. Here are the most common examples of industrial seed oils to keep in mind: - Canola (rapeseed) oil - Corn oil - Cottonseed oil - Grapeseed oil - Peanut oil - Rice bran oil - Safflower oil - Soybean oil - Sunflower oil Not only is seed consumption at such a massive scale new to the human diet, but all of these oils are also high in an omega-6 polyunsaturated fatty acid (or PUFA) [called linoleic acid](/content/blog/linoleic-acid-facts/index.html). ## Are Seed Oils Toxic? Current data suggest that “toxic” is an appropriate word to describe high linoleic seed oils, especially when heated, and especially in the amounts most people consume them today. Toxicity isn’t only acute, it’s also directly dependent on the amount and concentration of a substance taken over time — hence the saying “the dose makes the poison.” For example, artificial _trans_ fats won’t kill you with a single serving but are considered toxic because they significantly increase the risk of heart attack and stroke when included as part of your regular diet. Similarly, exposure to toxic chemicals found in secondhand tobacco smoke is associated with around 34,000 deaths of nonsmokers from heart disease each year in the U.S. alone. ## Are Seed Oils Safe? According to Merriam-Webster, the basic definition of safety is “the condition of being safe from undergoing or causing hurt, injury, or loss.” Proving a food or drug is unsafe or safe is actually different from showing that it’s toxic or conversely, doesn’t meet the definition of toxicity. ## Seed Oils, Health Claims, and Regulation Today, new food ingredients and pharmaceutical drugs undergo testing, clinical trials, and other safety checks before being sold for human consumption. Regulators and safety experts apply various criteria for the safety of prepared food versus food ingredients versus drugs, and so on. The first industrial seed oils made their way into modern diets in the late 1800s. Even though the first industrial seed oils had vocal critics about their health claims, health claims were largely unregulated. Modern safety assessments of many of these oils have revealed significant gaps in the early research that favored their inclusion in the food supply. ## _In Vitro_ Cell Studies on the Toxicity and Safety of Seed Oils Cell studies — done on living cells but in a laboratory setting, outside of organisms — are the simplest and most direct way to study toxicity. ### Linoleic Acid and Immune Cells A 2004 cell study comparing the effects of bathing T lymphocyte cells in a high concentration of either linoleic acid or oleic acid found that linoleic acid caused immunologically harmful effects. ### Animal Studies on the Toxicity and Safety of Seed Oils Studies on animals allow for a better understanding of toxicity and safety. These studies have looked at the effects of seed oils and linoleic acid on atherosclerosis, the brain, metabolism and obesity, and cancer. ## Linoleic Acid and Cancer While there are no well-designed long-term human trials on the effect of dietary linoleic acid and cancer outcomes, this omega-6 fatty acid does promote tumor growth in some animal studies and is linked to breast cancer and lung cancer in observational studies. ## Human Clinical Trials and Observational Studies on the Toxicity and Safety of Seed Oils Now that we've examined cell and animal studies in-depth, it's time to look at existing human evidence on the toxicity and safety of seed oils. Unfortunately, early human seed oil studies weren’t designed to look for harm caused by consuming linoleic acid and seed oils. ## Higher Incidence of Cancer-Related Death In the 1960s, the American Heart Association conducted a clinical trial to examine the effects of a diet high in polyunsaturated fats. The study resulted in an increased rate of death by cancer documented in the experimental group. ## What Should You Eat Instead of Seed Oils? In general, it’s best to steer clear of any fat that’s high in easily-oxidized omega-6 fatty acids. Look for fats and oils with high smoke points for cooking and ensure your fats are higher in heart-healthy monounsaturated fats. Opt for fats that are environmentally sustainable. ### What Are the Worst Seed Oils for Your Health? The eight worst seed oils to avoid include: - Canola (rapeseed) oil - Corn oil - Cottonseed oil - Grapeseed oil - Rice bran oil - Soybean oil - Safflower oil - Sunflower oil ## Conclusion It’s clear that at best, seed oils come with potential risks and offer no unique benefits, and at worst, could be driving major declines in public health around the world. ## Frequently Asked Questions (FAQs) About Seed Oil Toxicity and Safety ### Is Vegetable Oil the Same as Seed Oil? No, they’re not the same. Vegetable oils are any oils or fats derived from crops, including seeds.