However, not all fats are benign. The industrially processed, highly refined seed oils that are high in omega-6 fat are not recommended because they can cause inflammation and adversely affect human health. These oils include sunflower, corn, canola, safflower, and vegetable oils. In particular, do not use these vegetable oils at high heat because they release harmful chemicals called aldehydes when heated. Stay away from deep-fried foods and all hydrogenated (trans) fats.