Everyone already knows that
trans-fats are evil, but there are still a few things out there that have them. Here's some that I can think of:
1. Cake Frosting and Glazes
Most of these products have 1.5g of trans-fats per serving.
2. Milk
I should point out that milk contains a negligible amount of
trans-fats. That's why you won't see it listed on the nutritional label.
I can't think of any other foods that have
trans-fats, so I guess I'll just write about their chemistry. In the simplest sense, a
trans-fat is the
trans isomer of a fatty acid. If you don't know about cis-trans isomerism, I'll briefly explain. First of all, this only applies to double bonds. A molecule exhibits cis isomerism when its hydrogens are both on the same side of the double bond. Trans isomerism is the opposite; the hydrogens are across from each other. Here's an example:
Both of these structures represent the chemical called 1,2-dichloroethene. However, they differ slightly. The structure on the left has both hydrogens on the same side of the double bond, and the one of the right has hydrogens across from each other. Therefore, the one on the left is the cis isomer, and the one on the right is the trans isomer.
The same concept applies to trans-fats. Here are two more chemical structures:
Both of these chemicals have a formula of C18H34O2. They only differ in stereochemistry (the spatial arrangement of the atoms within a molecule). The top structure is the trans isomer because the hydrogens are on opposite sides of the double bond, and bottom structure is the cis isomer. You may recognize the top and bottom structures as elaidic acid and oleic acid, respectively. These are the fatty acids that you typically encounter in food items. Elaidic acid is most likely the trans-fat found in the cake frosting above. Its cis isomer, oleic acid, is usually found in plant products like olive oil, for instance.
No one knows why the trans isomers of fatty acids are so bad for people. According to Wikipedia, humans don't have an enzyme capable of metabolizing the trans isomer, so it builds up in arteries and kills people. I have no idea if that's true or not. There weren't and citations in the article that supported this claim.
By the way, I gave up italicizing the words cis and trans. I have better things to do with my life than to go back and fix it.