The American Heart Association suggests that 8 to 10% of daily calories should come from polyunsaturated fats. A good diet should seek to decrease the consumption of saturated fat and reduce blood cholesterol. Animal fats are rich in saturated fats.
While choosing the type of fat that we should consume in our diet, it is best to avoid trans-fatty acids or trans fats. Heating liquid vegetable oils make trans fats in the presence of hydrogen gas and a catalyst. This process is called hydrogenation. Partial hydrogenation makes the oil more stable and less likely to turn rancid. Fat is converted into a solid and functions more like margarine or shortening.
Partially hydrogenated oils can withstand repeated heating. These do not break down and so are ideal for frying fast foods. Trans fats are also found naturally in beef fat and dairy fat, although in small amounts. Trans fats raise bad cholesterol and lower good cholesterol. These are particularly bad for the heart, blood vessels and generally are bad for our health.
When taken in moderation, unsaturated fats help bring down blood cholesterol levels to replace harmful saturated fats. Unsaturated fats stay liquid at room temperatures. Some examples of food where these are found in high concentrations are olive, peanut, and canola oils, avocados, nuts like almonds, hazelnuts, and pumpkin and sesame seeds. These are examples of foods that are rich in monounsaturated fats.
Sunflower, corn, soybean, flaxseed oils, walnuts, fish, and canola oil are good polyunsaturated fatty acids sources. Canola has both mono and polyunsaturated fat. Omega 3 is unsaturated fat. While fish is a good source of this type of fat, these are also found in flax seeds, walnuts, canola oil, and soybean oil.
There are regional preferences for the type of fat consumed in food. Nutritionally speaking, a combination of plant-based oils is probably the best.