Organic acids consisting of carbon chains with a carboxyl group at the end. The nutritionally important fatty acids have an even number of carbon atoms, commonly between twelve and twenty-two.
Saturated fatty acids are those in which every carbon atom carries its full ‘quota’ of hydrogen atoms, and therefore there are only single bonds between adjacent carbon atoms.
Unsaturated fatty acids have one or more carbon-carbon double bonds in the molecule. Chemically these double bonds can take up hydrogen, which is the process of hydrogenation, forming saturated fatty acids. Fatty acids with only one double bond are termed mono-unsaturated, oleic acid is the main one in fats and oils. Fatty acids with two or more double bonds are polyunsaturated fatty acids, often abbreviated to pufa.
Unsaturated fatty acids lower levels of cholesterol in the blood, while saturated fatty acids raise it. To reduce the risk of heart disease, it is recommended that saturated fatty acid intake should not exceed about 10% of energy.
In general fats from animal sources are high in saturated and relatively low in unsaturated fatty acids; vegetable and fish oils are generally higher in unsaturated and lower in saturated fatty acids.
In addition to their accepted names, fatty acids can be named by a shorthand giving the number of carbon atoms in the molecule (e.g. C18), then a colon and the number of double bonds (e.g. C18 : 2), followed by the position of the first double bond from the methyl end of the molecule as n- or ω (e.g. C18 : 2 n-6, or C18 : 2 ω6).
