Today’s episode is a discussion about the types of fat currently being used in food manufacturing and the restaurant industry to replace trans-fatty acids. We also discuss a recent meta-analysis published in the Annals of Internal Medicine about organic foods.
I’d like to expound a bit on the chemical structure of fatty acids and why that is important.
Fats are essentially chains of carbon. All carbon atoms must have four bonds; no more and no less. This means that when carbon is organized in a long chain two of the available bonds are attached to other carbons, and the remaining two bonds are attached to the most abundant atom in the universe: hydrogen. This type of fat, when all the available bonds are saturated with hydrogen, is known as a saturated fat.
The picture below is a representation of a saturated fat called palmitic acid. The black balls represent carbon, the white balls represent hydrogen, and the red balls at the end represent oxygen.
When fats are saturated they naturally take the shape of a kind of flat zig-zag structure because this is the most stable form. This can allow for the fatty acids to neatly stack against each other, making them nearly always solid at room temperature.
By contrast, unsaturated fatty acids have one or more double bonds in the carbon chain. This produces kinks that prevent the fatty acids from forming a solid.
The main difference then, chemically speaking, between butter and oil is that the fatty acids in oil are chock-full of double bonds.
Where do trans-fats come in?
In the latter half of the 20th century saturated fats began to acquire a bad reputation. Various kinds of studies began to show that saturated fat was associated with heart diseases and cancers.1 Unsaturated fats, on the other hand, were largely considered to be healthier. Two problems though: when making biscuits or cookies or any number of other baked goods you really cannot substitute oil for butter.2 The second problem was that unsaturated fats are prone to oxidation and rancidity.
What do we do about this? Well, there was a process called hydrogenation that developed in the early 20th century to try and increase the shelf life of vegetable oils and fish oils. The resulting fats were actually more shelf-stable (because they were resistant to oxidation), cheaper to produce, were delicious, and could easily replace butter or lard in a recipe. This made them desirable to the food industry. Moreover, the fatty acids, although structurally similar to saturated fatty acids, were in fact unsaturated.
In most naturally occurring unsaturated fatty acids, the hydrogen atoms are on the same side of the double bonds of the carbon chain (cis configuration — from the Latin, meaning “on the same side”). However, partial hydrogenation reconfigures most of the double bonds that do not become chemically saturated, twisting them so that the hydrogen atoms end up on different sides of the chain. This type of configuration is called trans, from the Latin, meaning “across.” The trans configuration is the lower energy form, and is favored when catalytically equilibrated as a side reaction in hydrogenation.
The fact that these fats were technically unsaturated led some health advocates to push for saturated fat to be replaced with trans-fat in common food products. Unfortunately, as we all know now trans fats are far worse than saturated fats in almost every way, at least in terms of human health.
Recently we’ve all been privy to the slow removal of trans fats from the food industry. Carrie and I discuss how it’s being done and what the implications might be.
- I’m not going to discuss the reasons for it in this blog post, but suffice it to say when saturated fats (as opposed to unsaturated fats) become incorporated into the lipid membranes of cells it starts to disrupt cell function. Membranes need to have a certain amount of fluidity and flexibility, but if they made up of mainly saturated fats then the cell membrane becomes rigid and it’s more difficult to do housekeeping chores like importing nutrients, exporting waste, cell signaling, etc. This is not the only reason for saturated fats negative health effects, but it’s a major one.
- Actually you can, but you won’t like the results.