Type of fats
Fats and oils are practically always mixtures of different fatty acids in varying proportions. Hence the degree of saturation of the different fats and oils depends upon their various fatty acids content, as you can see in the table above.
Saturated Fats (SAFAs):
Animal meats, butter, whole milk, and some tropical plant oils, such as palm and coconut, are the main sources of saturated fats. Most of these fats are solid at room temperature. Saturated fats contribute to raise the level of LDL (bad) cholesterol with potential health consequences. They should, therefore, be consumed with moderation as part of a balanced diet.
Monounsaturated Fats (MUFAs)
Most animal and vegetable fats contain monounsaturated fats, but in varying quantities. They are usually in liquid form at room temperature, but they may begin to solidify if it is chilled. Monounsaturated fats are the most desirable type of fat in the diet because they help to decrease the LDL (bad) cholesterol in the blood and help to increase the HDL (good) cholesterol. Good sources of monounsaturated fat are olive oil, canola oil, peanut oil, and most nuts. Olive oil has the highest percentage (about 77%) of monounsaturated fats of any edible oil.
Polyunsaturated Fats (PUFAs)
The main sources of polyunsaturated fats are seeds, nuts, grains, and vegetables. Polyunsaturated fats are usually in a liquid state at room temperature and also when chilled. They lower the overall cholesterol level, but they also reduce HDL or good cholesterol. Recommended daily allowances of polyunsaturated fats should be part of a balanced diet.
Essential fatty acids
Among Polyunsaturated fats we find the two most important fatty acids: linolenic acid, also known as omega 3 fatty acid; and linoleic, also known as omega 6 fatty acid. These two are called “essential fatty acids” because they are essential for to life and health.
The omega number describes where the important carbon atom is located on the fat molecule. If this atom is third from the end, the fatty acid is known as omega 3 fatty acid (omega is the last letter of the Greek alphabet and means “end”). If it is sixth from the end, it is known as an omega 6 fatty acid.
The body requires about twenty fatty acids in order to live and operate. However, the human body can make them all but two of these: linolenic and linoleic. They can only be supplied by food or supplements. Omega fatty acids are a type of polyunsaturated fats that are especially healthy. They have a valuable role in reducing the risk of heart disease by lowering the blood pressure, protecting against plaque build up in the arteries and building healthy brain cells.
Vegetable oils, specially linseed oil, rapeseed oil, soybean oil and walnut oil are the principal sources of omega 3 fatty acids together with seafood. Sunflower seeds, sesame, walnut, soybean, corn and their oils are food sources especially rich in Omega 6 fatty acids.
Trans fatty acids
Trans fatty acids is a common term for unsaturated fatty acids with two hydrogen atoms situated at different sides of a double bond. Trans double bond(s) may occur in both mono- and polyunsaturated fatty acids, and in both cases the structure around the affected double bond is changed to a structure closer to that of a saturated bond, see figure below. TFA have melting points that are intermediate between cis-unsaturated fatty acids and saturated fatty acids.
The three main origins for Trans Fatty Acids (TFA) are bacterial transformation of unsaturated fatty acids in the rumen of ruminant animals, industrial hydrogenation and deodorisation and during heating and frying of oils at high temperature.
The effect of TFA on coronary heart disease (CHD) is greater than that of Saturated Fatty Acids (SAFA) at equivalent dietary level. Indeed, not only does TFA increase the LDL or “bad” cholesterol like SAFA, but it also decreases the HDL or “good” cholesterol and increases the blood level of triglycerides.
However, given current intake levels of TFA compared to SAFA in Europe, their potential to significantly increase CHD is much lower than that of SAFA (source: TRANSFAIR study 95/96).
TFA = 0.5%-2%
It is impossible neither to distinguish the health effects of TFA from natural or industrial origin nor to distinguish them analytically.
Hydrogenation is widely used by the food industry to transform unsaturated fats of the liquid form into saturated fats (please refer to the Processing section).
Hydrogenated fats are mainly used for margarine, shortenings products as well as bakery and confectionery products.
As with any type of food containing saturated fat, food containing hydrogenated or partially hydrogenated fat should be enjoyed in moderation in order to maintain a balanced and healthy diet.