Our preference for healthy oils is influenced by region, diet, and culture. The American Heart Association suggests 8 to 10% of daily calories should come from polyunsaturated fats. A good diet should seek to decrease saturated fat consumption and reduce blood cholesterol. Animal fats are rich in saturated fats.
When choosing the type of fat that we should consume in our diet, it is best to avoid trans-fatty acids or trans fats. The process of heating liquid vegetable oils converts them into trans fats. This is done in the presence of hydrogen gas and a catalyst. The 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. Trans fats are not healthy oils.
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 our health.
When taken in moderation, unsaturated fats help reduce blood cholesterol levels to replace harmful saturated fats. Unsaturated fats stay liquid at room temperature. 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 and could be categorized as healthy oils. Canola has mono and polyunsaturated fat, which would also fall in the category of healthy oils. Omega 3 is unsaturated fat. While fish is a good source of this type of fat, it is also found in flax seeds, walnuts, canola oil, and soybean oil.
The Mediterranean diet comprises an abundance of plant foods, fresh fruit, and olive oil as the principal source of fat, dairy products, fish, and poultry, and low in saturated fats (7-8%). The total fat of this food ranges between 25 to 35%. This is an example of healthy food (Willet et al., 1995). This diet is beneficial to health, good for the heart, and protects the body from some forms of cancer (Trichopoulou et al., 1997).
A good diet should seek to decrease saturated fat consumption and reduce blood cholesterol by consuming more fruits, vegetables, whole grains, fish, poultry, and less red meat. This diet will protect the body from cardiovascular diseases (Krish-Etherton et al., 2001; Hu., 2003).
Polyunsaturated margarine with plant-based phytosterols reduced cholesterol absorption in the gut and lowered blood cholesterol levels. This reduces heart disease risk by up to 25% (Law, 2000).
There are regional preferences for the type of fat consumed in food. Nutritionally speaking, a combination of plant-based oils would be considered healthy oils.