Reusing cooking oil can be safe if done carefully, but not all oils are created equal, and some should never be reused at all. According to food scientist Jennifer Pallian, B.Sc., RD, repeatedly heating oil causes it to break down, producing toxic compounds and free radicals that contribute to inflammation, high blood pressure, and even certain cancers. The risk only grows with each reuse—especially if you’re using the wrong kind of oil.
The worst offenders? Seed oils like soybean, sunflower, corn, cottonseed, and canola. These are high in polyunsaturated fats, which break down rapidly when exposed to high heat. They form harmful byproducts such as aldehydes and trans fats, which can linger in your food and build up in your body over time. Though often marketed as “heart healthy,” these refined oils are chemically processed, prone to oxidation, and best avoided—especially for frying.
If you must reuse oil, choose one with high heat stability and a cleaner fat profile. The best oils for frying and occasional reuse include tallow, ghee, coconut oil, avocado oil, and even peanut oil. These fats contain more saturated or monounsaturated fats, making them more resistant to heat-induced breakdown.
To reuse oil safely, always strain out food particles after frying, store the oil in an airtight container away from heat and light, and avoid heating it past its smoke point. If the oil smells rancid, looks dark, or smokes easily, it’s time to toss it.
