Fatty acid is an aliphatic carboxylic acid made up of a hydrocarbon chain with a terminal carboxyl group. Fatty acids are usually derived from fats (triglycerides). Fatty acids are important sources of fuel in the body because, when metabolized, they generate large amounts of energy. Heart muscle prefers mostly fatty acids as a source of energy. When fatty acids are not attached to other molecules, they are called free fatty acids. They leave the cell to be transported for use in another part of the body.
On the basis of saturation, fatty acids may be divided into two types –
Saturated fatty acids: Fatty acids that contain single bond in their carbon chain are called saturated fatty acids. Saturated fatty acids are harmful for our health because, they increase our serum total cholesterol and LDL cholesterol level, and increased risk of coronary heart disease.They include acetic acid, palmitic acid, butyric acid, lauric acid, capric acid, formic acid, myristic acid, and stearic acid. The main sources of saturated fatty acids are meat and dairy products, and some vegetable oils including coconut oil and palm oil. Most experts strongly advise limiting consumption of saturated fatty acids.
Unsaturated fatty acids: Fatty acids that contain one or more double bonds in their carbon chain are called unsaturated fatty acids.
Monounsaturated fatty acids: They contain one double bond. Dietary monounsaturated fatty acids are beneficial for our health because, they reduce our serum total cholesterol and LDL cholesterol, and increase HDL cholesterol, which protect against coronary heart disease. They include oleic acid, palmitoleic acid, and elaidic acid. Monounsaturated fatty acids are usually derived from vegetables and fish.
Polyunsaturated fatty acids: They contain two or more double bonds.
|Polyunsaturated fatty acid||Family||Source|
|Linoleic acid||Omega-6||Corn, soyabean, peanut, and cootonseed|
|Alpha linolenic acid||Omega-3||Linseed oil|
|Arachidonic acid||Omega-6||Animal fat|
|Timnodonic acid||Omega-3||Cod liver oil, mackerel oil, menhaden oil, and salmon oil|
|Cervonic acid||Omega-3||Fish oil|
Omega-6 fatty acids: The first double bond of these fatty acids begin at the sixth carbon atom. Omega-6 polyunsaturated fatty acids decrease our serum total cholesterol and LDL cholesterol, but also decrease HDL cholesterol that protect against coronary heart disease.
Omega-3 fatty acids: The first double bond of these fatty acids begin at the third carbon atom. Dietary omega-3 polyunsaturated fatty acids reduce serum triglyceride level, reduce the tendency to thrombosis by inhibiting thromboxane A2 synhesis, suppress cardiac arrhythmias, and substantially decrease the risk of cardiovascular mortality, but they have minor effect on LDL cholesterol or HDL cholesterol level.
Essential fatty acids:
Two fatty acids linoleic acid and linolenic acid are called essential fatty acids because of these fatty acids cannot be synthesized by the body and must be supplied in the diet. Linoleic acid is the precursor of arachidonic acid which is the substrate for eicosanoids synthesis. If linoleic acid is deficient in the food, arachidonic acid becomes essential. Essential fatty acids are required for fluidity of biological membrane structure and formation of eicosanoids. Essential fatty acids deficiency leads to development of scaly dermatitis, poor wound healing, hair loss, decreased vision and altered learning behaviors.
Trans fatty acids: Trans fatty acids are chemically classified as unsaturated fatty acids, but they behave more like saturated fatty acids in the body. Trans fatty acids do not found in plants, only found in small amounts in animal fats. However, trans fatty acids are produced during the hydrogenation of vegetable oils, for example, during the manufacture of margarine. Trans fatty acids rise serum LDL cholesterol and increase the rish of coronary heart disease.
Short chain fatty acids: containing 4 – 10 carbon atoms, for example, acetic acid is a short chain fatty that contain 2 carbon atoms. For oxidation of short chain fatty acids, they can enter into mitochondria without difficulty.
Long chain fatty acids: containing 11 – 24 carbon atoms, for example, stearic acid is a long chain fatty acid that contain 18 number of carbon atoms. For oxidation of long chain fatty acids, they must be bound to carnitine to penetrate the inner mitochondrial membrane and gain access to mitochondria.