Should you cook with seed oils, or replace them with olive oil, ghee and tallow?

Ben GreenfieldMS · exercise physiologist, NSCA and ISSN certified by his own account, no clinical credential

Replace them. Cook with extra-virgin olive oil, ghee or tallow, and treat fried restaurant food as the worst offender.

What it rests onHe makes two arguments and both matter. The mechanistic one: polyunsaturated oils oxidise readily, the resulting oxidised linoleic acid metabolites impair mitochondrial function, heated oils form 4-hydroxynonenal, and damaged fats are incorporated into cell membranes where they cannot be metabolised away the way excess sugar can, which is why he writes 'I would rather mow through an entire bag of sugar than consume just about any fried food on the face of the planet'. The precautionary one, stated explicitly: 'There is a huge necessity for long-term research to fully understand the health implications', which he treats as a reason to avoid now rather than a reason to wait. His main citation is Joseph Mercola's linoleic acid work in Nutrients, and Mercola sells the alternative fats at scale. He also links two tallow-fried chip brands, both of which have pages in his own product catalog.

Gil CarvalhoMD, PhD · nutrition and aging researcher, creator of Nutrition Made Simple!

Keep cooking with them, especially in place of butter, lard or tallow.

What it rests onHe concedes the chemistry and disputes its consequence, which is the part a headline drops. On oxidation he writes that polyunsaturated fats are chemically less stable, especially when heated, that trial results on oxidation products are inconsistent, and that seed oils also carry antioxidants such as vitamin E, and then argues that disease outcomes rather than laboratory biomarkers should drive the recommendation, noting that high consumers do not show more oxidation-related disease. On inflammation he cites dozens of randomised trials that consistently fail to detect a rise in inflammatory markers, with some detecting a fall. On hexane he notes it is used in refining many oils including coconut, is largely evaporated before sale, and that cold-pressed versions exist. He also concedes a contextual point that narrows the fight: most seed oil intake arrives inside ultra-processed and fast food, which is a different question from cooking with canola at home.