Dear 100 Hour Board,
All the cookies I buy say have "no trans fat". Why are my cookies so transphobic?
-Never eating cookies again
Are you ready? Because it's time for IUPAC Nomenclature and Nutritional Biochemistry with Ento! Let's begin.
First, what is trans fat? Trans comes from Latin, meaning "across", "on the other side", or "beyond". The opposite is cis, which comes from the Latin for "on this side of". In organic chemistry, these terms are used to describe the orientation of groups around a carbon-carbon double bond (or any other carbon-carbon bond that can't rotate freely). If a bond is cis, that means that the carbons on either side of it are on the same side, while trans means that the carbons are on opposite sides. For example, here are the structures of cis-2-butene and trans-2-butene, respectively (source).
The vast majority of naturally occurring unsaturated fats (fats with at least one carbon-carbon double bond) are cis. Ruminant animals, like cows and sheep, have low levels of naturally occurring trans fat in their milk and body fat produced by bacterial fermentation during digestion, but almost all the trans fat in a normal person's diet is artificial, and it comes from something called partially hydrogenated oil, or PHO. We'll get back to PHO in a minute.
So how are trans fats different from cis fats? Well, fats are made of a series of long carbon chains with a few things in the middle. Every time you have a cis double bond, it creates a permanent bend in that chain. Saturated fats (no carbon-carbon double bonds) can stack together (a.k.a. crystallizing) very easily, because they don't have any permanent bends in their chains, but cis unsaturated fats can't. That's why coconut oil, butter, and lard are mostly solid at room temperature, but vegetable oil has to get really cold before it will be solid. For several decades, we've pointed our fingers at saturated fat as the major cause of heart disease and stroke, while unsaturated fats were seen as healthy. The problem is, it's really hard to make a lot of the best foods that we love without solid fat. So what was the solution? Partially hydrogenated oil.
When you hydrogenate oil, you turn unsaturated fats into saturated fats. But when you only hydrogenate the oil partially, some of double bonds will stop halfway through the reaction and go back, but when they go back to being unsaturated, there's nothing keeping them from being trans instead of cis. In fact, trans is actually more favorable, and enzymes in living things are the only reason that most natural fats are cis in the first place. Trans unsaturated fats, unlike their cis counterparts, don't have any bends in the chain, so they have no problem being solid at room temperature, but they're also not saturated. It's a win-win situation, right? Well, not quite. In the 1990s, we started to notice that trans fats are actually worse for you that saturated fats. In fact, recent studies (like this one) appear to show that getting rid of saturated fat doesn't make you less likely to have a heart attack, stroke, or diabetes, as was previously thought, while getting rid of trans fats definitely does reduce the risk of heart disease. In 2006, the declaration of trans fat content on the Nutrition Facts panel became mandatory in the United States, and many companies started removing or reducing trans fat in their products, including Crisco, as a result. Last summer, the FDA declared that PHO was no longer generally recognized as safe, meaning that it could not be used in food except with special permission following research-backed justification that it was safe. Food manufacturers have until July 2018 to completely remove PHO from their foods, because changes like that take time, but PHO has already disappeared from most foods in preparation for that deadline.
In conclusion, you should be glad that the cookies that you buy don't have any trans fat. If you still don't want buy them, that's fine; homemade cookies are loads better anyway.
Back in the day, my family used to get these awful little double chocolate cookies that were absolutely loaded with Crisco (and thus trans fats) from Smith's. They were the worst things I've ever tasted, but the weird thing was that you couldn't stop eating them. I hated them passionately, but if my parents brought some over to my apartment today I would still probably eat like five of them. Those stupid addicting dumpster cookies.
Anyways, here's a funny trans tomato comic I saw a while ago for your troubles: