Q&A on Trans Fats

I recently spoke with Professor Levente Diosady, a chemical engineer at the University of Toronto on the topic of trans fats. Professor Diosady has been working in the field of edible oils for more than 40 years. He had some very surprising things to say about trans fats.
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First off, what exactly is a fat?
A fat is a triglyceride molecule. There are typically 18 carbons with one, two, three or four double bonds. The unsaturated bonds can have two configurations. They can be cis or trans. If the chain continues on the same side of the carbon then we have cis, if the chain comes in on one side of the carbon and goes out the other it's called trans. In nature, in a chemical process, the cis and trans have approx the same probability of forming. However in most animals and plants the double bonded fatty acid are built up enzymatically and are inevitably in the cis form.

What is the difference between fats with the cis form and the trans form?
The naturally occurring long chain fats, unless they are coming from a dairy animal, are always in the cis form. The cis form has a relatively low melting point. Typical vegetable oils are liquid at room temperatures and contain one, two or three double bonds. If you need to have a product which has a solid or plastic fat then you have to do something to raise the melting point. There's only two ways to raise the melting point: One is by incorporating saturated fats which naturally have a high melting point or incorporating trans fats which have an almost as high melting point as the saturated fat.

How do you chemically alter a fat to be a solid at room temperature?
To obtain a hardened fat, like a margarine or butter, you can use a process called hydrogenation where you attach hydrogen atoms to the double bonds. if this reaction goes to completion the double bond is used up and it becomes a single bond and is no longer cis or trans. If you fully hydrogenate a fat in effect you eliminate all cis or trans double bonds.

If there any problems with this process?
The problem comes from the fact that these processes occur fast on the catalyst. Usually they are hydrogen starved. As a result some of the double bonds pick up one hydrogen abut then give that hydrogen up and rearrange in the process. Instead of having all cis, up to 50 or 60 per cent of the bonds will reform as trans. In the typical process you are forming some trans double bonds.

Why have we only been talking about trans fats in the last few years?
Historically these were not thought to be negative. There a positive thing in terms of the process [of hydrogenation] itself because you use a lot less hydrogen to get a higher melting point because the trans have high melting points. But research in the 1970s has shown that the body doesn't recognize trans fat as an unsaturated fat. It recognizes it as if it is a saturated fat. In effect it doesn't incorporate it into the body. Instead it burns it up for energy just as if it were a saturated fat. Earlier studies have shown that in terms of developing arteriole plaques and cholesterol deposits trans fats behaved very much like saturated fat. There was a very good ground-breaking study by a pair of researchers in 1981 which was the first one to show that trans fats do contribute to heart disease. Even to this point it was thought to essentially be equivalent to saturated fat.

What changed?
About four or five years ago there were a series of well-designed studies that showed that [trans fats] were somewhat more harmful than saturated fats and it was picked up by the popular press and everybody else. Everybody got onto the band-wagon to get rid of trans fat. It's been something we've been saying as researchers for 30 years but now it had momentum. The problem that has been presented to the public has been exaggerated. The trans fats are worse than saturated fats but they're not 50 times worse or 100 times worse. Maybe 5 or 10 per cent worse.

So what should people be conscience of when it comes to trans fats?
It's a good idea to avoid trans fats, because after all your body is not designed to metabolize them and they aren't terribly good for you. The fact is having an excess amount of any kind of fat is bad for you and having saturated fats has long ago been shown to be bad for you. The only way you can get solid fat is by having saturated fat, usually a short-chain saturated fat. Now margarine has no trans fats but its absolutely loaded with tropical oils because there is no other way around it. Even though there is some very good research, the fact still remains that you need a certain amount of saturated fat in the product to give you the functionality: The melting characteristics so that it's spreadable but melts in the mouth. Trans fats are there. They are undesirable but they are not nearly as dangerous as the public was lead to believe. Nonetheless I'm all for trying to eliminate them.

So trans fats occur naturally?
A number of natural products contain them in small amounts. Not huge amounts. A whole slew of microbial oils and in some conditions under normal conditions for example.

Can we consume them safely?
Sure. You look at the demographics. This stuff has been eaten in large quantities for 60 years. We didn't see people dropping dead from trans fats. They are dropping dead from heart disease because they are eating way too much fat period. The fact is you can have a small amount. It is desirable to limit that to as small an amount as possible. I think [consumption of trans and saturated fat] should be minimized but they can't be eliminated unless you want to eliminate all solid fat products. That would eliminate half the bakery products in the world. You can't really make bakery products with an oil you need to use a shortening which is partially solid fat.