----- "Ben Liberman" <[log in to unmask]> wrote: 
> At 6:04 PM -0700 4/1/10, Belinda Lawson wrote: 
> >Could you please clarify what is PUFA? 
> 
> Polyunsaturated fatty acid 
> 
> >something-something-fatty-acids maybe? 
> > 
> >And could someone please point me to Harris' site? 
> 
> http://www.paleonu.com/ 

Thanks Ben, and apologies to Belinda and anyone else who was in the dark about what I was talking about. I should be more careful about how I use acronyms and name-drop, since people on the list are joining the conversation at many different stages. 

To clarify a bit further, fatty acids are classified as either saturated, polyunsaturated, or monounsaturated (SFA, PUFA, MUFA), according to their chemical structure. Specifically, the terms indicate the number of "double bonds" in the fatty acid molecule. SFAs have no double bonds because they are fully saturated with hydrogen atoms. MFAs are slightly less saturated with hydrogen atoms, having one double bond, and PUFAs have two or more double bonds. Saturation and unsaturation affect the stability of a fatty acid. SFAs are the most stable, that is, least prone to oxidation. 

Note that actual fats, outside of chem labs, are blends of different kinds of fatty acids. Beef fat is, as I recall, about 55% SFA, 40% MUFA, and 5% PUFA--but that's from memory, so it may be off a bit. Lard has a bit more MUFA and less SFA. Coconut oil is overwhelmingly SFA, which is why it can be stored at room temp without going bad. If you make pemmican from rendered beef fat, using mostly the hardened white fat, you end up with more of the SFA stearic acid, which is why pemmican can also be stored for long periods at room temperature without going rancid. I often use a slow cooker to make pot roast, and when it's done, a good bit of that saturated white fat (tallow) has been rendered in the cooker, so I just scoop it up and save it for use in cooking. 

Olive oil has more MUFA than anything else, but still has a substantial amount of PUFA. 

The so-called "essential fatty acids" (EFA) that you hear about are the omega-3 and omega-6 PUFAs. They are, indeed, essential, because our bodies can't make them. There should, however, be a balance between the omega-6 and omega-3, because these fats have a powerful effect on a number of processes, including inflammation, clotting, and vasoconstriction. In addition, some people, such as Kurt Harris, argue that the absolute amount of PUFA that we ingest should be sharply restricted, because that is our "EM2"--this is Harris's abbreviation for "evolutionary metabolic milieu." That's just another way of saying that before the advent of industrial processes for extracting vegetable oils, we didn't have much PUFA in our diet. He (and others) adduce increasing evidence that PUFA, along with fructose, is implicated in non-alcoholic fatty liver disease (NAFLD), which he believes to be a major player in metabolic syndrome, type 2 diabetes, and related problems. 

I hope that little summary is helpful. 

Todd Moody