*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. So 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 each carbon atom is linked to a hydrogen atom: because 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.

As an example of how a monounsaturated fat would be written, let’s take oleic acid, of extra-virgin olive oil fame: this would read ‘18C:1n9’, indicating that it is 18-carbons in length [‘C18’], has one double-bond [‘:1’], and that the double-bond occurs 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 position. 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’.