Good FatsFats that are liquid or soft at room temperature are polyunsaturated fatty acids, which are found primarily in vegetable oils such as palm, corn, safflower, sunflower, flaxseed, and canola oils. Polyunsaturated fats are also the main type of fat found in seafood.
Essential fatty acids, such as linoleic acid and alpha-linolenic acid, are specific polyunsaturated fatty acids that are needed to maintain cell structure and produce hormones. These are in a sense the "good fats" - essential fatty acids that must be obtained from the foods we eat. The remaining type of fatty acids to be concerned with are monounsaturated fatty acids, found mainly in vegetable oils such as canola, olive and peanut oils.
Bad Fats (Trans Fats)When food manufacturers add hydrogen to vegetable oil, a process called hydrogenation, trans fats are created. Trans fats extend the shelf life and flavor stability of foods, such as vegetable shortening, crackers, cookies, and snack foods. However, these are the bad fats for the heart.
The American Heart Association (AHA) guidelines state that people should limit trans fats to 1% or less of their total daily calories. By comparison, the U.S. Dietary Guidelines urge Americans simply to keep their intake as low as possible. This means that for someone eating 2,000 calories daily, trans fat intake should be no more than two grams per day.