Well riddle me this, dieticians and naysayers to the well-known health benefits of partially hydrogenated vegetable oils: If it, the oil, is not a solid at room temperature (typically about 20 degrees F below that of the average human body), but is instead a liquid, then it is most likely a liquid while it is travelling through your veins and arteries, lubricating vital portions of your body.
Why, exactly, is this deleterious to ones’ health? Is it too THICK and VICIOUS of an oil, sticking and slowing the circulation of blood within the body? Or are there some wierd chemical properties of trans fats which are damaging to our cellular structures or something like that?
Someone once told me that trans fats build up in the colon, thereby lining it with a nice 10 foot long membrane of thick, gelatinous, impenetrable goo which inhibits the absorbtion of vital nutrients through the colon. If you fast longer than 10 days, it was said (corroborated by someone else who was listening) that this tapeworm-appearing thing will come out your anus, thereby scaring the living hell out of you, but also making you glad that you no longer have the equivilent of axle grease lining your large intestine any more.
First off, fats and oils inside your body do not resemble fats and oils outside your body. The chemical properties that determine the melting point and viscosity of fats and oils do have something to do with their healthfulness, but melting point and viscosity themselves don’t. Not going into too much detail, fats and oils aren’t in their solid or oily form in your body. Your body – mostly your liver – produces soap-like substances that surround the fat and dissolve it in much the same way that soap dissolves fats and grease on clothing and dishes. In this dissolved form, the fat can cross through your intestines into your bloodstream.
So, the stuff about lubricating your blood vessels isn’t true. The stuff about trans fats building up in your colon is absolutely untrue. It sounds like the people involved were just into some kind of fad ‘detoxification’ diet that required a ten-day fast. This idea that foods contain ‘toxins’ that build up in your body is not scientifically sound – your liver is constantly breaking down toxins that come both from foods (all foods, including ‘natural’ foods) and from many of your body’s chemical processes. And your kidneys and large intestine are constantly removing these (mostly) broken-down ‘toxins’ from your body. There is certainly not a thick greasy membrane of trans fats from fatty foods lining your intestines.
Now, the simplest way I can explain why trans fats are bad does involve looking at the three pictures in the above link. On the bottom is a saturated fatty acid – a long, straight molecule. For various reasons, the shape of this molecule makes it unhealthy, partly because a lot of them can be packed into a small area. In the middle is an ordinary (‘cis’) monounsaturated fatty acid. This molecule has a ‘kink’ – it’s bent, and it’s harder to pack a lot of them into a small space. (This is one reason why monounsaturated fats tend to be liquid at room temperature.) This kind of fat is healthier than a saturated fat.
Now, the trans fat on top has the same straight, un-kinked shape as the saturated fat, even though it’s not saturated. Basically, this means that it resembles a saturated fat in your body. Trans fats are deceptive – they’re technically not saturated fats, but they’re nearly as unhealthy as saturated fats because the molecules have the same shape.
The current anti-trans fat fad is mostly based on a misunderstanding of how bad trans fats actually are. In reality, they’re mostly just unhealthy fats masquerading as healthier, unsaturated fats. The real danger to health is probably slightly less than saturated fat – or, at the very worst, they could potentially be very slightly more dangerous than saturated fat. Something that’s very important to remember is that most foods don’t contain a very large amount of trans fats, and only foods made with artificially hydrogenated oils contain any. Examples include margarine and foods fried in hydrogenated oils such as donuts, fries and fried chicken.
Follow-up with clarification: My interpretation of the OP’s first paragraph was that the poster thought hydrogenated oils stayed liquid at room temperature; the WebMD articles, however, indicate otherwise. I have no idea (other than reading Roches’s post) what a liquid oil does inside your body.
Hydrogenated oils are (for the most part) solid at room temperature – that’s the whole point of hydrogenation. Saturated fats, because the molecules are linear and can pack together easily into a solid, have a lower melting point than unsaturated fats, which are harder to pack. Hydrogenation is turning unsaturated fats into saturated ones by adding hydrogen, usually in the presence of a nickel catalyst. The original, and still probably the most important, purpose of hydrogenation was to produce fats that are solid at room temperature out of cheap, widely available liquid oils derived from plants. This is more cost-effective than using animal fats, which are mostly saturated and therefore solid at room temperature. One of the slight advantages to using hydrogenated fats in the place of solid animal fats is that they’re cholesterol-free. For a time, when cholesterol was the #1 fad health concern, margarine made from hydrogenated vegetable oil seemed a much better choice than butter.
My understanding (please correct me if I’m wrong) is that trans-fats are partially saturated fats where there are gaps in the saturatation. A fully saturated fat molecule has hydrogen atoms attached along the entire length of the molecule, at every spot where it is possible to attach a hydrogen atom. A partially saturated fat molecule has hydrogen atoms attached to only some of the spots along the molecule. It’s a trans-fat if the hydrogen atoms are attached along the fat molecule in such a way that there are unsaturated points between the saturated points. If all the hydrogen atoms are attached at one end of the fat molecule, it’s not a trans-fat.
The problem with trans-fats is that they tend to promote LDL cholesterol at the expense of HDL cholesterol. LDL cholesterol tends to cause atherosclerosis. HDL cholesterol tends to prevent atherosclerosis by sweeping LDL cholesterol out of the bloodstream.
The problem with partially hydrogenated oils is that people don’t know how to control where the hydrogen atoms are attached to the oil molecules. Thus, partially hydrogenated oils are high in trans-fats. Naturally occurring saturated fats like those found in butter, chocolate, etc. tend to be lower in trans-fats.
The main reason health authorities used to encourage people to use margarine is that margarine is less saturated than butter and so raises cholesterol less than butter does. Then people figured out that cholesterols are not all alike, and that different types of saturated fats promote different types of cholesterols. The standard advice now is to stay away from partially hydrogenated oils. Butter is now believed to be better for you than margarine.
As far as I know, monounsaturated fats are still the best, as they tend to raise HDL cholesterol and lower LDL cholesterol. Olive oil is a good source of monounsaturated fat.
You are kind of right, Jeff. The trans label identifies the configuration about the unsaturated (double) carbon-carbon bond. Double bonds in hydrocarbons can be cis or trans. Cis means there rest of the carbon chain continues on the same side of the double bond; Trans means they are on diagonally opposite sides of the double bond. Because of the geometry of the bond, this means that Trans fats have relatively straight molecules, whereas Cis fats have a definite kink in the molecule. More info here: http://www.nutriwatch.org/09Reg/trans.html
This German page has an image that helps to illustrate this, although it is not directly related to fats.