November 13, 2012

Fat Tuesday -- Part Deux!

It’s Tuesday, so you know what that means…

It’s Mardi Gras! Or, for the English speakers among us, Fat Tuesday! Yes, it’s back – the weekly series where I don the helmet, the pads, the mouth guard—everything I can manage (except the cup!)—and tackle the toughest thing this side of a 250-pound linebacker:  sixty years of misinformation from health experts and government nutrition authorities regarding dietary fat.

If you’re just tuning in, take a minute to catch up on the first post by clicking here. It’ll bring you up to speed on how every type of fat and oil is a combination of saturated, mono-, and polyunsaturated fatty acids. So when we hear the buzzline about saturated fat being found in animal products (especially…*gasp!*… red meat), and olive oil being so good for heart health because it’s monounsaturated, that’s the truth, but it sure ain’t the whole truth and nothing but the truth, so help you God. Olive oil is almost 15% saturated and beef fat is almost 42% monounsaturated. In fact, the fat that’s the most saturated is not an animal fat at all, but coconut oil. Yes, from a plant. EEK! There goes the neighborhood.

Anyway, there’s so much to cover concerning fats that it’s hard to know where to start. In the interest of keeping things simple and trying to organize the zillion-and-one things I want to say about fat into some semblance of logical order and cohesion, the natural place to go after the intro is to talk about the differences between saturated, monounsaturated, and polyunsaturated fats. So much of what I want to get into regarding which fats are best for cooking and which are truly“heart healthy” depends on us understanding these basic facts, so hang on to your hats. Or, rather, your hiking boots and canteens, ‘cuz we’ve got a lot of ground to cover.

One of the difficult things to do when we talk about fats is to separate even the word “fat” from all the connotations—or should I say baggage—it’s accumulated over the last couple of decades. Like I said in the first post of this series, it’s important for us to divorce the biochemical and physiological facts from the politically correct dietary guidelines (reduce fat and especially saturated fat) and the media hype (nuts are good for you, avocados and salmon are good for you, but you’ll drop dead on the spot if you eat a piece of bacon or—heaven help you—an egg yolk). It’s a tall order, I know. But do your best. It’s just a word. It doesn’t imply anything all by its lonesome. It only has the power we assign it, so let’s take away the fear. Let’s take away the negativity, at least for right here, right now. (When you’re done reading this, you can go back to watching the news or reading a magazine where they’ll tell you how bad fat is.) You can do it. Believe me. If I can go from putting soy milk on my bran cereal and light margarine on my whole grain toast for breakfast to heavy cream in my coffee and a 3-egg omelet fried in beef tallow, you can pretend you’ve never heard anything bad about fat.

BUT...before I get into things this week, we have a tiny bit of housekeeping to do. There’s an important point I forgot to make last week, and we need to cover it before we go on. Last week, I explained that every kind of fat and oil is made up of different classes of fatty acid, based on saturation. But those classes of fatty acids are themselves just larger categories that encompass lots of different fats.

Say what? (I would say, “What’chutalkin’ ‘bout, Willis?! But I don’t know if anyone reading this would get that. Am I alone in loving 1980’s pop culture references? Answer: no. This girl digs ‘em, too.)

I know, it’s a little confusing. Think of a big box of crayons. If red is a class of color, then burgundy, dark red, red-orange, magenta, and red-violet all fall under that classification. They’re different from each other and each has a unique look, but ultimately, they’re all some kind of red. That’s how fats work. Within the classifications of saturated, monounsaturated, and polyunsaturated, there are different kinds of fats, usually identified by name but also by the number of carbon atoms and double bonds they have. Within each of the three classes, there are several different fats (20-30 plus, in fact). Here are just a few examples:

Saturated:  butyric acid (4 carbons), lauric acid (12 carbons), caprylic acid (8 carbons)
Monounsaturated:  oleic acid (18 carbons), palmitoleic acid (16 carbons)
Polyunsaturated:  linoleic acid (18 carbons), arachidonic acid (20 carbons)

For this post, when I say “fat,” I’m referring to fatty acids. Fats are made up of carbon, hydrogen, and oxygen. (And dirty hypodermic needles, bubonic plague, and everything else nasty that will kill you instantly. HA! Just kidding. You know me better than that by now.) They’re chains of carbon atoms strung together with hydrogen atoms sticking out of them, and a couple of oxygen atoms on one end. (Think of them like strings of Christmas lights. The carbon atoms are like the wire and the hydrogens are the lights strung along it.)

In terms of biochemistry, saturated fat means one thing:  it means that the molecule has no double bonds between carbon atoms. That’s it. It does not equal a heart attack, atherosclerosis, or obesity. It just means there are no double bonds. (The bonds are saturated with hydrogen atoms, hence the name, saturated. This ain't rocket science, people.) In chemistry shorthand they look like this (in two different representations):

Pretty much a straight line; not a whole lot of funk to this shape.

Monounsaturated fatty acids have one double bond between carbons. (Mono means one…remember your Greek and Latin prefixes everyone? I hope so, because they’re huge in terms of where all the names for these complicated things come from. Who’da thunk it? My beloved English background blending so nicely with my new love for biochemistry. Will wonders never cease?)  Monounsaturated fats (like oleic acid, the one olive oil's mostly made of) are thought of as "heart healthy." Like I said last time, they're the one fat all the warring factions (vegans, low-carbers, dieticians, doctors, and Paleo adherents) seem to agree on. Whether they really are good for heart health I'll cover in a future post. For now, just know that somehow, for reasons that have nothing to do with actual biochemistry, this magical little double bond has been anointed with the powers to prevent everything from hardened arteries to that one sock disappearing down the black hole in the dryer. Aaaanyway, whenever there’s a double bond in the carbon chain, it creates a bend or kink in the shape. Depending on where the double bond is, the shape can vary, but they generally look like this:

See the double bond? And that's where the carbon chain bends.

Polyunsaturated fatty acids have more than one double bond. (Poly meaning multiple.) And if one double bond is good for you, more must be better, right? Right? (Actually, no. Why not? Tune in next Tuesday.) Each of the double bonds causes a bend in the molecule, so polyunsaturated fatty acids have the most interesting shapes of the three classes of fatty acids. There are a bunch of different ones, but here are a few, and they look like this:

Two double bonds make this one more curved than the monounsaturated fat above. 
Also, FYI, this is an omega-6 fat. It's called that because the first double bond from the end without the oxygen atoms (the O's that you see at the upper left) happens on the 6th carbon. 
This bad boy has 5 double bonds! That's why it's so curly.
(The name also comes from those Latin & Greek roots: eicos [20, for 20 carbons]
and pent, like pentagon [meaning 5, for 5 double bonds].) This is EPA, an omega-3 fat found in fish oil. The first double bond in from the end without the oxygens happens at the 3rd carbon.

1, 2, 3, 4, 5, 6...SIX double bonds! Ah, hah hah hah!
(Sorry...just channeling the Count from Sesame Street there for a sec.)
Docos = 22 (22 carbons); hex = 6 (6 double bonds). This is also an omega-3.

*Note: All the images above are from the best book ever written about fats. Yes, the best one: Know Your Fats, by Mary Enig, PhD, except the saturated fat, which I bummed from Wikipedia.

The shape of each fatty acid (as determined by the number of double bonds) confers different properties on them. Saturated fats can be thought of as straight in shape, and because of that, they pack together tightly and are usually solid at room temperature. (Like butter and the fat on bacon or surrounding a nice, thick steak.) The exceptions to this are the tropical plant oils (coconut and palm), which are solid at room temp in colder climates but are liquid in warmer weather. 

Monounsaturates are liquid at room temperature but they solidify when they get cold. Well, maybe not solidify, exactly. Maybe “congeal” is a better word. (To test this out yourself, put some of your olive oil in the refrigerator. If it starts to solidify after a while, it’s the real deal. If not, it’s been cut with cheaper oils. Huh? Yep, the food industry is up to its usual shenanigans and sometimes adds lower-quality oils [which don’t even come from olives!] to bottles sold as olive oil and doesn’t say so on the label. Ever wonder why olive oil has gotten so cheap? Economics of scale, sure, but there are also some wily goings on behind closed factory doors.)

Polyunsaturates are liquid even when cold, like flax oil, fish oil, and most of the seed and grain oils, like sunflower and corn oil. If you’re wondering how they take liquid soybean oil and turn it into solid vegetable shortening and margarine, we’ll cover that in a future post. (Sneak peek: that’s what partial hydrogenation is, and it is capital N-A-S-T-Y, nasty.)

That’s it for today’s lesson, kids. Just the shapes and a little preview about what they mean. Next time, we’ll go into detail on how all those double bonds affect what happens when those oils are extracted and processed, heated up in a pan or deep fryer, and crammed down our pieholes…um…I mean, drizzled over a nice salad or placed lovingly on our dinner plates. 

Have questions about fat? Ask away in the comments section, or send me an email.  

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