The Low Down on PUFAs

Thanks SteveO and SteveF.   My eyes are being opened to the complexities of omega-3 metabolism.   I get it:  all those cis-double bonds are fragile: easily oxidized either in the body or in the bottle.   I also appreciate the Jaminets caution in regard to over-consumption of omega3s espec in supplement form;  about 1 lb per week of fish is their recommendation.  The piece about DHA and angiogenesis was also eye-opening.  My take-home message is:  don’t overdo the omega3s, especially as supplements.  Thanks so much!  —B

Dear B,

FYI only:  It is not the cis double bonds that are unstable, but rather the hydrogen atoms on the immediately-adjacent carbons.   The double bonds “activate” the adjacent carbon atoms to make their “saturated” hydrogens easy to oxidize.

Once this is clear, it is easy to see why polyunsaturated fats are so unstable; they have two (2!) next-door double bonds.  So the adjacent hydrogens are trapped between two double bonds and are doubly activated.

This double activation is non linear (it is way more than twice single activation).

Saturated: no activated H.  Coconut oil.  Palm oil.
Monounsaturated: 4 single-activated H: Linoleic acid.  Olive oil.
Diunsaturated: 4 single-activated H, 2 double-activated H. Linolenic.
Tri-unsaturated: 4 single activated H, 4 double-activated H. GLA. ALA.
Tetra-unsaturated: 4 single-activated H, 6 double-activated H. Arachidonic acid.
Penta-unsaturated: 4 single-activated H, 8 double-activated H. EPA.
Hexa-unsaturated: 4 single-activated H, 10 double-activated H. DHA.

The single activations are significant; olive oil has a much shorter shelf life than coconut oil.

But it is the double activations that oxidize when you look at them cross eyed.
This is why PUFAs are the body’s perfect choice for oxidation sensors.

Fun and games with chemistry.  —Steve

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