Cooked vegetable oil worsened inflammation in the colon, enhanced tumor growth, promoted gut leakage, and caused harmful bacterial products to leak into the bloodstream in mice.

This study used canola oil which is high in polyunsaturated fatty acids (PUFAs) as are other vegetable oils such as soy and corn. PUFAs are prone to oxidation which was shown to be the mechanism causing damage in this study.

Other cooking oils and fats that are not high in PUFAs such as avocado oil, olive oil, coconut oil, and butter are not likely to have the same effect. One thing to keep in mind is that olive oil has a low smoke point so when frying things at very high temperatures avocado oil may be a better option since it has a high smoke point.