During this week’s Metabolic Classroom lecture, Dr. Ben Bikman explores the connection between seed oils—specifically linoleic acid—and insulin resistance, a growing area of interest and controversy in the metabolic health world.

Ben begins by detailing the historical rise of seed oils like soybean, corn, sunflower, and canola oil in the human diet. Once used for industrial purposes, they have now become the most common source of dietary fat, with soybean oil consumption increasing from zero to over 20 pounds per person per year in the U.S.. This rise coincides with a global increase in insulin resistance, prompting the question: Are seed oils to blame?

Dr. Bikman focuses on linoleic acid, the primary omega-6 polyunsaturated fat in seed oils, and differentiates between the fat itself and its oxidation products, such as 4-HNE and 13-HODE. He cites cell culture studies showing that unoxidized linoleic acid doesn’t impair insulin signaling, but its peroxidation products dramatically compromise insulin receptor function and glucose transport. Animal studies further support this by showing that diets high in linoleic acid lead to insulin resistance, obesity, and elevated inflammatory markers, while animals consuming fats like coconut oil fare much better.

However, when it comes to human studies, the picture becomes more complex. Some clinical trials suggest that diets high in polyunsaturated fats can improve insulin sensitivity—but these diets are almost always high in carbohydrates, and rarely test seed oils in a low-carb context. Dr. Bikman proposes a unifying theory: saturated fats may be more problematic when consumed alongside carbohydrates, because insulin shunts them into ceramide biosynthesis, a direct driver of insulin resistance. Linoleic acid, on the other hand, becomes dangerous when it undergoes peroxidation, especially in high oxidative stress environments or when used in cooking.

Ben concludes that context matters. Linoleic acid is present in all natural fats and can’t be avoided entirely—but its overconsumption through refined seed oils, particularly in fried foods or highly processed products, is likely harmful. He encourages consumption of natural fats from animals and fruits (like coconuts and olives), rather than industrial seed oils, especially for those concerned about metabolic health and insulin resistance.

Show Notes/References:

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