Fatty Acid Peroxidation & Free Radicals

Double bonds are formed in fatty acids when two adjacent carbon atoms each have one hydrogen atom taken away. The process is called desaturation. The double bond can be in two forms. Cis with both missing hydrogen atoms on the same side or trans when the two missing hydrogen atoms are on opposite sides.

Here is a graphic for the 18 chain saturated fatty acid Stearic (18:0):

Cis Double Bond fatty acids
Notice now the Oleic (diagram below) is missing 2 hydrogen atoms on the bottom side at the 9th & 10th carbon atom from the left end. That it starts on the 9th carbon atom is what makes it a Omega 9 family fatty acid.

The unbalanced (top verus botom) repulsive forces created between hydrogen atom to hydrogen atom forces the double bond to bend in the direction of less repulsive forces and it is this bent and open double bond which causes Oleic (18:1w9) to be more susceptible to free radical attack than the saturated form. It also alters it's chemical properties and makes it a more valuable and biochemically active fatty acid than the saturated form 18:0.

Like Omega 3 LNA, EPA, DHA and Omega 6 LA, we do need some of these double bond rich fatty acids in our diet, just not too much.

Here is the 18 chain monounsaturated single double bond cis fat Oleic (18:1w9):

Trans double bond fatty acids
Note in the graphic below, the double bond in the trans faty acid starting at the 9th carbon atom from the left end has the hydrogen atom on the 10th carbon on the bottom instead of the top, as in the normal cis form above. Normally trans fatty acids are not health friendly and are formed when fatty acids with cis double bonds are heated. Note also that this trans configuration results in the fatty acid not bending as the repulsive forces have been made equal top and bottom. This non bendable trans double bond fatty acid form is why you should avoid any RBD (Refined, Bleached and Deodorized) oils or fats as the processing tends to alter the normal & healthy cis double bonds into unhealthy and straight trans double bond fatty acids.

Here is the unhealthy 18 chain monounsaturated single double bond trans fatty acid Oleic (18:1w9 trans)

Hydrogenation is another process which alters normal cis double bonds by elimination them entirely (filling in the missing hydrogen atoms) in an effort to reduce the peroxidation / rancidity / spoilage rate of the oil / fat. This is achieved but at a cost of the loss of the unique biochemical effects of the double bonds. Hydrogenation is how margarines are made from cheap RBD veggie oils by removing all the double bonds (filling them in with the missing hydrogen atoms) and thus the resultant saturated fatty acids can pack together tightly and be made to physically resemble butter. Not my cup of tea!

Peroxidation is the dark side of double bond fatty acids as their carbon atom to carbon atom double bonds are much more easily attacked by free radicals than the more normal and common carbon to carbon single bonds.

It is estimated the first double bond in a fatty acid is 50 x more susceptible to free radical damage than zero bond saturated fat and for the second and following double bonds the susceptibility to free radical damage goes up another 40 x per bond.

Intake of foods and/or supplements with antioxidant vitamins and its impact on CHD

"The tendency of unsaturated lipids to undergo oxidation is related to the number of double bonds in the fatty acid molecule. Each additional double bond after the initial double bond found in monounsaturated fatty acids increases susceptibility to peroxidation by forty fold while a fatty acid with one double bond is about fifty times more susceptible to peroxidation than a saturated fatty acid. Hence, a fatty acid with three double bonds is oxidized eighty times as readily as a fatty acid with only one double bond. This oxidative susceptibility of fatty acid is reflected by the tendency of various oils to oxidize. "

From this we can construct a table of the various fatty acids and their sensitivity to peroxidation assuming saturated is 1.

1) Zero bond saturated = 1
2) One bond Omega 9 OA (monounsaturated) = 50
3) Two bond Omega 6 LA (polyunsaturated) = 90
4) Three bond Omega 3 LNA (polyunsaturated) = 130
5) Four bond Omega 6 AA (polyunsaturated) = 170
6) Five bond Omega 3 EPA (polyunsaturated) = 210
7) Six bond Omega 3 DHA (polyunsaturated) = 250

So polyunsaturated Omega 6 LA (18:2w6) is 90 times more susceptible than sat fats due to its 2 double bonds (50+40):

And polyunsaturated Omega 3 LNA (18:3w3) is 130 times more susceptible than sat fat due to it's three bonds (50+40+40):

It is these double bonds which give these fatty acid molecules their unique properties and also elevated free radical damage susceptibility.

We only need about 2 - 3 g of Omega 6 LA and 2 - 3 g of Omega 3 LNA. Anymore can be damaging and excessive Omega 6 LA is very bad (body wide) and should be aggressively eliminated from the diet as veggies will provide ALL the Omega 6 LA anyone needs.

A recent US expert working committee recommends the following:
Polyunsaturated fatty acids in the food chain in the United States

Omega 6 LA < 6.7 g (this is the hard bit as Omega 6 LA is everywhere)
Omega 3 LNA ~ 2.2 g (1 tablespoon of ground organic flax)
Omega 3 EPA+DHA ~ 0.65 g (1 - 2 serves a week of salmon, tuna, mackerel,herring, sardines or 2 fish oil capsules a day)

This is ALL the Omega 3 and Omega 6 you need for Optimal Health.

Now that you have a basic understanding of fatty acids, imagine what happens if you hydrogenate a double bond fatty acid by forcing hydrogen atoms into all the places in the double bonds that are lacking them. The result is a once beneficial fatty acid now made into a totally saturated form, if totally successful or full of half way conversion horrors (trans fats, double bond position shifts, etc) if not.

Click for a graphic of the fatty acid analysis of various oils, fats and fat rich food:


and here is a Interactive Excel spreadsheet which will allow you to input your daily intakes and have your relative peroxidation risk calculated:

OilAnalysis.xls (Requires Microsoft Excel)

The bottom line is that small amounts of Omega 3 and Omega 6 are very beneficial to your health and reduced CVD risk. Just realize you may open pandora's box if you over do the powerful Omega 3 & 6 fatty acids. Never in our Paleo past, did we ever consumed more than small amounts of these fatty acids and neither should you.

This means giving up the veggie oils and margarines as these are very un-natural foods.

I eat about 25 g a day of Virgin Coconut Oil (VCNO), 15 g of ground flax (1 tablespoon), 5 g of Extra Virgin Olive Oil (EVOO) and 2 g of fish oil (normally from fish but sometimes from fish oil capsules). You do not need more. The VCNO is used for cooking, baking, morning smoothies and the EVOO is mixed 45 - 45 with the VCNO and some ground flax for salads.

Optimal Health, Happiness & Long Life,
Greg Watson