*Geek Box: Fatty Acids

*Geek Box: Understanding Fatty Acids

If you read nutrition research enough, you’re going to read a lot about dietary fatty acids, some of them with mind-boggling names [thankfully we have acronyms!]. Fatty acids are characterised by their chemical structure, with two key aspects:

1. how long they are [i.e., their ‘chain length’], and;
2. how saturated they are.

The chain length reflects the number of carbon atoms. For example, ‘C18’ in the case of ALA means 18-carbon atoms in length. In addition to length, fatty acids are characterised by saturation. What this means is that the extent to which each carbon atom is linked to a hydrogen atom: if every carbon atom has a corresponding hydrogen atom, the fatty acid is saturated with a single-bond [all carbon and hydrogen bonded together]. A saturated fatty acid is written as the number 0. So, if you read ‘C18:0 stearic acid’, you know that this fatty acid is 18-carbons in length and is saturated.

Unsaturated fats, however, have a double-bond, where instead of each carbon atom being bonded with a hydrogen atom, two carbon atoms are bonded together instead. So, ‘monounsaturated’ fats are fatty acids with a single double-bond [‘mono’], while polyunsaturated fats have 2 or more [‘poly’]. These fatty acids will have the position of their double bond written into their nomenclature.

For example, the monounsaturated fat, oleic acid, would read ‘18C:1n9’, indicating that it is 18-carbons in length [‘C18’], has one double-bond [‘:1’], and a double-bond at the 9th position in the chain [known as the ‘omega’]. Hence, oleic acid is an ‘omega-9’ fatty acid. Because polyunsaturated fats have multiple double-bonds, they are written according to where the first double-bond is positioned. So ‘C18:3n3’ ALA, indicates that this is an 18-carbon length fatty acid, with three double bonds, and the first double-bond occurring in the n3 position: hence the fatty acid is an ‘omega-3’.