Saturday, 6 December 2008

Polyunsaturated oils

Many health organisations recommend using oils consisting primarily of polyunsaturated fatty acids (PUFA's for short). The most widespread of which is sunflower oil. We're told these oils are good for the heart so I decided to have a look into the facts.

Understand that there are two separate issues important here:

  1. The health aspects of polyunsaturated fatty acids
  2. The health aspects of extracted oil made from those fatty acids

Different kinds of polyunsaturated fatty acids

PUFA's can be divided into two groups: Omega 3 and Omega 6. For years and years the experts thought the two were identical in their health benefits but lately omega 3 seems to have got the limelight. Science has now shown that too much Omega 6 PUFA's are actually unhealthy.

Omega 3 fatty acids

Three important Omega 3 fatty acids are Alpha-Linolenic acid (ALA), Eicosapentaenoic acid (EPA) and Docosahexaenoic acid (DHA). Your body CANNOT make the ALA so you have no choice but to get it from your diet. Linseeds and walnuts are naturally rich in ALA – and thus are both highly recommended by me so go out and buy them now.

ALA by itself has a plethora of health benefits, but as I previously blogged the Omega 3 fatty acids that are good for your brain are DHA and EPA. Your body CAN covert ALA into EPA and EPA into DHA as long as your diet is a healthy one. Natural sources of EPA and DHA are fish and algae (Vegetarians may purchase it from the following: ).

Omega 6 fatty acids

Three important Omega 6 fatty acids are Linoleic acid (LA), Gamma-Linolenic acid (GLA) and Arachidonic acid (AA). Your body CANNOT make LA, so again you have no choice but to obtain it from your diet. Then once ingested the body can convert LA into the other Omega 6 fatty acids. Now here is where it all goes pear shaped...

Those ever so many health organisations that push sunflower oils and other LA rich products as the saviour for your heart fail to mention an important fact. And that is that our diets are way too rich in LA already, we certainly don't need more LA. Sunflower oil for example may or may not be healthy but since we already have a surplus of LA it is simply a non requirement.

Health benefits of PUFA's

PUFA's do lower cholesterol. We all know the drill here right? High levels are associated with higher rates of heart disease and lower rates are vice versa. But it is important to note though, that PUFA's lower both LDL (the bad type) and HDL (the good type) cholesterol and those populations that have low levels of heart disease do not consume much PUFA's at all.

Health dangers of PUFA's

PUFA's are prone to rancidity and oxidation. These affect both the taste and the health properties of the fats. If you take whole nuts and seeds as an example, then their original packaging by nature protects the fragile oils with many anti-oxidants. When the oils are extracted, the packaging that nature intended to protect with is disregarded. Thus these extracted fats are far more likely to go bad than properly stored nuts and seeds.

If you do not want your arteries to rust up then always store your PUFA rich products in sealed containers in a refrigerator. Never ever overheat them.

Also an overload of Omega 6 fatty acids, particularly LA and AA compared to Omega 3 ALA will lead to inflammatory diseases like asthma and arthritis.


Nuts and seeds are very high in polyunsaturated fatty acids. These fats are very unstable, so it makes sense to eat them in their original packaging (i.e. as whole nuts themselves) and not use extracted polyunsaturated oils.

There are exceptions to this rule as sesame oil still contains many anti-oxidants and a large amount of more stable fats. These are called mono-unsaturated fatty acids and I will discuss them at a later date.


Dr. Art Ayers said...

I am very skeptical about all of the hype about raising HDL and lowering LDL. The research is very weak and the new study about the statin Crestor shows that only lowering inflammation makes a difference on heart disease -- lowering LDL doesn't make any difference. My bet right now is that saturated fats for lean people are no risk. Extra pounds means inflammation, and inflammation + saturated fats may be a problem.
Keep blogging!

Marie said...

Nice photos.