Holy cow…it’s Tuesday again. Did someone hit the fast-forward button on my life when I wasn’t looking? When I finish one of these posts, I think, great, six whole days for me to get my thoughts together for the next one. And then, BAM, it’s upon us again. Oh, well, no problem. ‘Cuz when it comes to fat, there’s only one thing I like more than writing and talking about it, and that’s eating it!
If you’re new here, I should warn you about what you’re getting into. I’m trying to set the record straight on over half a century of misinformation about dietary fat, and I’m taking you along for the ride. If you have the courage to question the “facts,” doubt the “experts,” and generally break all the rules, hop on board; our team needs all the firepower it can get!
Take a minute to read the previous posts in this series if you haven’t already. In part 1 and part 2, I covered some very basic information about fats, like how they’re all made up of combinations of the different kinds of fatty acids (saturated, mono, and polyunsaturated) and how the biochemical makeup of those fats determines their shapes. Last week I started to get into the good stuff. (Well, if you ask me, it’s all good stuff, but in terms of what you out there on the interwebs probably care about, last week was where we finally started talking about how the biochemistry of fats and oils can give us clues as to which are the safest ones to cook with, which are best for our health, and which are best used as industrial lubricants and put nowhere near our frying pans or our mouths. I’ve said it before and I’ll say it again: cotton is for wearing, not eating. So ix-nay on the cottonseed oil, capisce?)
I left off last last time with a hint that we’d be talking about the nastiest of the nasties today. Trans fats. What are they, and why are they so bad for us?
Recall from part 2 that saturated fats are solid at room temperature. (I don’t have to cue the scary music when I say “saturated fat” anymore because thanks to last week’s post, we’re not scared of it anymore. Woohoo!) And recall from part 3 that because saturated fats have no double bonds between carbon atoms (they’re saturated with hydrogen instead), they’re the most stable. They're the safest for cooking, and compared to mono and polyunsaturated fats, they’re the least likely to go rancid or develop “off” flavors.
|Hold my hand...this might get scary.|
Got your hiking boots on? Good. We’ve got a lot of ground to cover.
Thanks to the twin miracles of modern food technology and massive government agricultural subsidies, we are awash in ultra-cheap vegetable oils. Well, not really vegetable oils, more like grain and legume oils, since I’m mostly talking about corn and soy. A convergence of factors have led to the preponderance of these oils on supermarket shelves and in restaurant deep fryers. Mostly it was two things: 1) We grow so incredibly much corn and soy in the U.S. that we had to figure out something to do with all of it (besides feeding it to cattle), and 2) A couple of scientists in the 1950s thought they found the holy grail of what causes heart disease. They thought it was all the saturated fat and cholesterol we were eating, and the government ran with their recommendations for darn near everyone to avoid animal fats like the plague. (Note: they were wrong about this. Wronger than wrong. Like, so wrong that we are only beginning, sixty years later, to claw our way out of the immense black hole of wrongness this threw us into. More on this in future posts as we get deeper into the effects of different fats on our health.)
So we had tons of cheap vegetable oil and we were supposed to stay away from naturally occurring animal fats, like butter and lard. What’s a mad scientist to do? Well, if you’ve got a pioneering spirit and no working knowledge of human physiology, you create the process of partial hydrogenation. What this does is take unsaturated oils that are liquid at room temperature and make them solid or semi-solid. Brilliant! Now we can use things like soybean oil to make margarine, instead of being forced to use butter on our toast and practically dig our own graves every morning at breakfast. We can also use cottonseed oil to make vegetable shortening. Whew! And I thought we were going to have to resort to lard—y’know, the thing our 90-year-old great grandmothers made biscuits and pie crusts with all their lives before anyone told them they were killing themselves. (Nifty factoid: The name Crisco comes from “crystallized cottonseed oil.”)
Unfortunately, I do have to get my geek on and get a little down and dirty with the science for a minute. (I promise, there’s a method to my madness. I’m not trying to bore you, I swear! I’m trying to help this all make sense. I’ll make it as quick as I can…and maybe even a little entertaining.)
What hydrogenation does is it takes away some of the double bonds and adds hydrogens. (Now you know why it’s called that.) Let’s take a look at these to get a better idea of what happens on a biochemical level. Then, we’ll figure out what that means in terms of food and health.
The fatty acid on the left is saturated. It has no double bonds, so it’s not bent or curly. Because they’re straight, saturated fats can pack together tightly and that’s why they’re solid. The one in the middle is a monounsaturated fat. It has one double bond, so there’s one bend. It’s liquid at room temperature, but starts to solidify when it gets cold. Now let’s get to the bad boy on the right. That, my friends, is a trans fatty acid. It has the exact same chemical composition as the one in the middle – same numbers of carbons, hydrogens, and oxygens, BUT – and this is a very big deal – there is no double bond (between carbons). The double bond has been taken away and hydrogens have taken up the extra space. As we know, no double bonds, no bends. So the molecule is straight, BUT – and again, this is a big deal – it’s not the same kind of straight as the naturally occurring saturated fat on the left.
If you look closely at the trans fat on the right above, you’ll notice it looks a little twisted. Where they took away the double bond in the middle, the molecule twisted. Why did it twist and what does that mean? Glad you asked, because this is the key question, and the answer is the whole point of this post. Check this out:
The one on the left represents the monounsaturated fat in the middle in the graphic above, and the one on the right represents, well, the trans fat on the right. In the one on the left, the hydrogens at the double bond are on the same side of the molecule. In hardcore biochem-speak, this is called the “cis” configuration. (Cis from the Latin, meaning “on the same side.”) But in the fat on the right, when they take away the double bond and add the hydrogens, the hydrogens end up across from each other. This is a trans fat. (Trans meaning “across,” like a trans-Atlantic flight).
Pretty neat, huh? See, what we’ve done is, we’ve taken an oil that is normally a liquid and turned it into one that is a solid. This is how they make the margarine and shortening I mentioned before. This doesn’t sound like a bad thing. Margarine’s pretty great, isn’t it? It’s soft enough to spread straight out of the refrigerator without tearing your bread apart. You don’t have to let it soften like you do with butter. Score one for modern technology! Better living through chemistry! Wheeee!
So why do they only partially hydrogenate oils, instead of fully hydrogenating them? Well, sometimes you will see “fully hydrogenated vegetable oil” on a food label. Partial hydrogenation is just more common. The reason is, a fully hydrogenated oil would be more solid – like butter, or even a hard wax. And that kind of defeats the goal of spreadability for margarine and shortening. But there are some products where full hydrogenation is preferred, depending on the texture, shelf-life, and “mouth feel” the manufacturers are aiming for. Fully hydrogenated oils have no trans fats. WHAT?! Yes, it’s true. If an oil is fully hydrogenated, it means they got rid of all the double bonds (between carbons). And what do we know about a fat that has no double bonds? It can’t be trans, because it’s technically saturated. Now, as for the safety of these artificial fats, the jury’s out. They don’t have the same negative health effects as their evil trans brethren, but I’m not exactly rushing to shove ‘em down my throat at Christmas dinner, know what I mean?
Getting back to the “mouth feel” issue, let’s talk about how trans fats feel in our mouths. Trans fats don’t melt the same way natural saturated fats do. They impart a kind of waxy texture. You can test this by putting a little pat of butter in your mouth and letting it melt. Then do the same with a pat of margarine. It will not feel the same. (The margarine will feel—to use the technical term—gross. Even grosser if you try this with a low-fat spread!) You can do the same experiment with peanut butter. Most commercial brands of peanut butter use partially hydrogenated soybean or rapeseed (canola) oil. (Not to mention added sugar, molasses, and sometimes corn syrup.) The brands that are completely natural—no ingredients on the label but peanuts and salt—do not use trans fats. The mass-marketed commercial brand will coat the roof of your mouth in a way the natural kind doesn’t. Again, the best way I can describe it is a “waxy” feel.
Now, you might be thinking, “Okay, Amy, I get what trans fats are now. But how do they do it? How do they make these twisty, fake fats? Well, it involves some serious chemical shenanigans that are best described by the great folks at Wikipedia. Let’s just say it requires very high temperatures and things like nickel and palladium, which you definitely want near fats that will enter the food supply! (As we saw in part 3, high heat is public enemy number one when it comes to unsaturated fats. So I guess that’s not bad enough; let’s throw some palladium into the mix!) This is major-league funky, people. And remember, we’re supposed to stay away from processed foods. Last time I checked, I didn’t see any nickel catalysts required to get the cream to separate out of cow’s milk, and I’m pretty sure the meat guy at the farmer’s market I buy bacon from doesn’t use any palladium to get at that beautiful, beautiful pork fat.
Okay, this one’s getting long, so I’ll hit the pause button on trans fats for now. Next time, I’ll get to the thing that matters most – what all this means when it’s time to EAT. I mean, this hydrogenation stuff sounds like a food manufacturer’s dream come true – start with a cheap input (subsidized vegetable oil), and end up with a product that has a longer shelf life and a mouth-feel that sort of comes close to real fats (after all, margarine is closer to butter than corn oil is, right?), but has none of the problems associated with “arterycloggingsaturatedfat.” (Yes, didn’t you know it’s one word now? You can’t say “saturated fat” anymore without prefacing it with “artery clogging.” I’m pretty sure they passed a law on that one…) So what’s the big deal?
Do saturated fats really clog our arteries? Are trans fats really as bad for us as people say they are? And are all those "heart healthy" vegetable oils really heart healthy?
All will be revealed in due time. (Due time being the next few Tuesdays, of course.)
In the meantime, if you have any questions about fats—or anything else related to nutrition, food, or health, leave a comment or send me an email.
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