In today’s episode of the Healthful Pursuit Podcast, Dr. Cate Shanahan, a physician and nutrition scientist, joins Leanne Vogel to explore the overlooked effects of seed oils on metabolism, cravings, and overall health. Dr. Shanahan calls many industrial seed oils “dirty fuel” and argues that removing them from the diet can be at least as transformative as changes to carbohydrate intake.
Dr. Shanahan has helped popularize evidence-informed approaches to dietary fats, and her work emphasizes that the benefits many people attribute to low-carb or ketogenic diets may actually come from eliminating industrial seed oils. Across this conversation she explains how these oils damage cell membranes, drive oxidative stress, and alter metabolism in ways that increase sugar cravings and impair energy production. The interview offers practical guidance on safer fats, restaurant strategies, and how to prioritize nutrient-rich foods to reduce oxidative stress.
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Transcript
Dr. Cate Shanahan: These oils make us crave sugar. No matter how determined you are to cut sugar, if these oils are dominating your metabolism you will continue to be obsessed with sweet tastes.
Leanne Vogel: Welcome to another episode. Today we’re digging into oils—the damage some industrial seed oils cause, how they affect membranes, and practical ways to reduce exposure without living in fear. I want to be clear: my approach is balanced. I avoid the hateful oils most of the time, but I don’t insist on perfection. I prioritize education so people can recognize how certain foods make them feel and make different choices when possible.
Leanne Vogel: I aim to help women tune into their body’s signals and connect those signals to their choices—food, activity, and mindset. That’s how you make sensible, sustainable changes rather than living in doom and gloom about every ingredient.
Leanne Vogel: For practical help with restaurants, there are tools and apps that identify seed-oil-free options. You can also ask restaurants to cook without certain oils—servers and chefs are generally accommodating. The more customers request alternatives, the more common those options become.
Leanne Vogel: Our guest today is Dr. Cate Shanahan, a Cornell-trained physician-scientist whose work has influenced movements around bone broth, ferments, and seed-oil-free cooking. She’s worked with professional teams on performance nutrition and runs a telehealth practice and an educational site. Let’s hear from Dr. Shanahan.
Dr. Cate Shanahan: I’m excited to be here. Over the last few years the meaning of “keto” has shifted. What many people actually gain from going keto is removing industrial seed oils—soy, corn, canola, cottonseed, safflower, sunflower and a few others. That change, more than carbohydrate restriction alone, explains a lot of the improvements people experience.
Leanne Vogel: When you first started investigating oils, what clicked for you?
Dr. Cate Shanahan: My background is in biochemistry. When I learned about essential fatty acids and fatty acid structures, I realized certain polyunsaturated fats in industrial seed oils have multiple double bonds that make them highly vulnerable to oxidation. Oxidized lipids create free radicals that damage cell membranes and mitochondria. I wasn’t taught this in medical school, and once I saw the chemistry it made sense as a root cause for many chronic problems.
Dr. Cate Shanahan: Damaged membranes can’t let cells take in nutrients or signal properly. The result is a wide range of problems depending on which tissues are affected—skin issues, asthma, migraines, neuropsychiatric symptoms, impaired energy production and more. Because mitochondria have similar membranes, oxidative damage there undermines cellular energy production and contributes to insulin resistance and chronic disease.
Leanne Vogel: Which oils are most problematic?
Dr. Cate Shanahan: I call the worst offenders “the hateful eight.” The most important ones to remember are the three C’s—corn, canola (rapeseed), cottonseed—and the three S’s—soy, sunflower, safflower. The remaining two are less common on retail labels but are used in food service. Other oils—olive, avocado, butter, coconut, sesame, peanut—are generally fine. Some, like sesame or peanut, contain more polyunsaturated fat but are protected by antioxidants and long-standing agricultural selection that makes them more stable when used appropriately.
Leanne Vogel: So not all polyunsaturated fats are equal. Flax (high in omega-3) oxidizes much more readily than sesame (higher in omega-6) and therefore behaves differently when heated. That nuance is important for cooking choices.
Dr. Cate Shanahan: Exactly. Nature often pairs oils with antioxidants and other compounds that protect them in whole foods. Industrial extraction and large-scale food processing remove those protections and create oils that oxidize easily and become toxic when stored, heated repeatedly, or used in large quantities.
Leanne Vogel: What about deep frying?
Dr. Cate Shanahan: Deep frying can be done with more stable fats like tallow or coconut, but any oil can become unhealthy if abused—overheated, reused many times, or used to cook poor-quality ingredients. Deep frying also extracts reactive compounds from the food being cooked, which can contribute to oxidation. Ideally, limit deep-fried foods or choose kitchens that use stable fats and proper techniques.
Leanne Vogel: How should people store oils?
Dr. Cate Shanahan: Minimize light, heat, and oxygen exposure. Glass containers and cool, dark storage are better than plastic and warm shelves. Even so, the biggest factor is choosing inherently stable fats and avoiding industrial seed oils in packaged foods and food service.
Leanne Vogel: Where do these problematic oils show up most?
Dr. Cate Shanahan: Practically everywhere: packaged foods, snack items marketed as “healthy,” many restaurant kitchens, school and institutional food service. Always read ingredient lists. If any version of corn oil, soybean oil, canola/rapeseed oil, sunflower, safflower, or cottonseed oil appears, the product contains oils that are likely harmful when consumed habitually.
Leanne Vogel: How do we rank priorities—sugar, carbs, or oils?
Dr. Cate Shanahan: Seed oils change body fat composition and damage mitochondria so cells demand more sugar. That creates strong sugar cravings and makes carbohydrate restriction very difficult for many people. Cutting seed oils often reduces cravings and metabolic dysfunction significantly. You don’t necessarily need zero carbs, but you do need to control carbohydrate intake while also removing seed oils so your metabolism can recover.
Dr. Cate Shanahan: Oxidative stress—free radical damage—is the root mechanism. Avoiding seed oils is a major part of preventing oxidative stress, but so is eating nutrient-rich foods that supply antioxidants, protein, cholesterol, and the right fats. Foods such as eggs, shellfish, butter, vegetables, and herbs and spices help the body defend against oxidative damage.
Leanne Vogel: Practically, what should people do when they can’t avoid exposure—restaurants, special occasions?
Dr. Cate Shanahan: Use practical tactics: ask for foods to be cooked without added seed oils, bring your own dressing or oil packet when possible, choose establishments or cuisines that use butter, tallow, or olive oil, and focus your regular diet on whole foods high in antioxidants and protective nutrients. Small, realistic steps lead to big improvements over time.
Leanne Vogel: How can listeners learn more or connect with you?
Dr. Cate Shanahan: My website is the central resource where you can sign up for newsletters, access free guides, and learn about courses and resources I offer. I also share content on social platforms and encourage people to read and explore the science around oxidative stress and dietary fats.
Leanne Vogel: Thanks so much, Dr. Shanahan. This has been eye-opening. For more information and show notes, check the podcast episode page. We’ll see you next episode.
Disclaimer: This transcript is provided for informational purposes only and does not replace medical advice. Consult a qualified practitioner for personalized guidance.