The Science of Essential Fatty Acids

Essential fatty acids, or EFAs, are fatty acids (fats) that humans and other animals must get from their diet because the body needs them to function but cannot make them. The term "Essential Fatty Acid" refers to fatty acids required for biological processes but does not include the fats that only act as fuel.

Only two fatty acids are known to be essential for humans, these are sometimes known as parent fatty acids; Alpha-Linolenic Acid (ALA) (an Omega 3 fatty acid) and Linoleic Acid (LA) (an Omega 6 fatty acid). These essential fatty acids can be found in many nuts and seeds. More specifically: Omega 3 ALA in flaxseeds, hempseeds and walnuts and Omega 6 LA in seeds (e.g. pumpkin, sunflower, sesame, wheatgerm), nuts and wholegrains e.g. rice, barley.


The Science Bit….


Fats are made up of lines of carbon atoms all joined together by ‘chemical bonds’ Some carbons are joined together with one link, and some two. Where there are no double links then the fats are called ‘saturated’, where there are two links between the carbons they are called ‘unsaturated’. 

Where there is more than one double link, these fats are called ‘polyunsaturated’ – ‘poly’ referring to ‘many’. Where there are two bonds, they don’t tend to hold on to each other very well, and they can be altered easily.  Omega 3 & 6 fatty acids are polyunsaturated fats which means they can easily be damaged by heat or light.


Omega 3 & 6 Conversion Pathways:

The body needs to convert these parent Essential Fatty Acids into other fatty acid the body needs to function optimally. 


Omega 3 conversions:

ALA converts into:

Eicosapentaenoic Acid (EPA):

EPA is an important long chain polyunsaturated fat in the pathway shown above EPA, along with DHA, is needed for the normal function of the heart1. The conversion from ALA to EPA is understood to be inefficient. The next important Omega 3 fat, DHA is made following a series of conversions from EPA.

Docosahexaenoic Acid

DHA is the last long chain polyunsaturated fat in the conversion pathway, DHA is found in especially high concentrations in structure of eyes and brain tissue. DHA is needed for normal brain function and normal vision2.  DHA is also very important for babies and children’s brains and vision and for pregnant women, as DHA is needed for the normal brain development of the foetus3.

As DHA is the last long chain polyunsaturated fat in the conversion pathway it can be hard for your body to make enough of it from the parent Omega 3 ALA. The NHS, therefore advises to eat oily fish as it contains high levels of DHA. If you or your family struggle to eat the one portion of oily fish the NHS recommend a week, then you may want to consider supplementing with a high-quality, DHA rich, fish oil such as those from Efamol.

Omega 6 conversions

Western diets do generally contain higher levels of Omega 6 than Omega 3 as processed food and cooking oils contain refined plant oils like corn oil, palm oil and sunflower oil which are mainly made up of the Omega 6 fat Linoleic Acid.

This causes two problems for the body as too much Omega 6 LA can block the Omega 3 pathway, and as the Omega 6 LA found in these processed foods has been damaged, the body is then unable to convert it to GLA.

(GLA) Gamma Linolenic Acid:

Evening Primrose Oil and Borage Oil contain GLA, an Omega 6 nutrient that is not well represented in our diet.

EPO supplementation ensures that GLA, which is not commonly found in our modern diet is available, allowing the body to ‘skip a step’ in the conversion of Omega 6 fats. 

(AA) Arachidonic Acid:

Arachidonic acid is a polyunsaturated fat and is found in high concentrations in cell membranes, especially in the brain, where it is the second most abundant fatty acid after DHA. Arachidonic acid is found in low concentrations in fish oil. It is not found in Borage oils or Evening Primrose oil however GLA is readily converted to AA in the body.

  1. DHA and EPA contribute to the normal function of the heart. The beneficial effect is obtained with a daily intake of 250mg of DHA and EPA combined.
  2. DHA contributes to normal brain function and normal vision. The beneficial effect is obtained with a daily intake of 250mg of DHA.
  3. DHA contributes to normal visual development of infants up to 12 months. DHA maternal intake contributes to the normal brain development of the foetus and breastfed infants and to the normal development of the eye of the foetus and breastfed infants. The beneficial effect is obtained with a daily intake of 250mg of DHA plus an additional 200mg of DHA.

Food supplements should not replace a balanced diet and a healthy lifestyle.



Erasmus U, 1993, Fats that Heal, Fats that Kill, Alive Books, Canada

Holford, P 2004, New Optimum Nutrition Bible, Piatkus, London (Chapter 9)

Lecture: Omega 3 and Fish Oils, 22.03.11, Dr L Lindmark, Manchester