Oils and butters share the same chemical structure and properties. They are made up of a three-carbon skeleton (called glycerol) on which up to three chains or branches (fatty acids) can be attached, and they look like this:
These branches are distinguished by:
--> their length (the number of carbons they contain),
which can range from a few to 22. In most situations,
the longer the chain, the ticker the oil (liquid oil, soft or hard butter)
--> their form (how the carbons are connected to one another)
carbons can be joined together by a single or double bond.
a simple (or saturated) bond -C-C- gives the chain a straight path.
a double bond -C=C- (unsaturated) has the effect of blocking the chain locally at a given angle and tends to make the fat more liquid.
This appears to be a bit confusing at first glance, but it is critical to fully understand the difference between good fats and those to avoid. We are touching here at the health topic as this is more related to food cosmetics.
Saturated, mono- or polyunsaturated fats
Or the good, the bad and the ugly. Who is who ?
You may have previously heard these terms, they relate to the quantity of hydrogen atoms in the chain. Carbons have the particularity to bond 4 times. In the carbon chain of the fatty acid, 2 are busy for being linked to the neighbor carbons. Two are then left and atoms of hydrogen are taking this role for saturated fats.
Think about "saturated" as "it cannot take anymore hydrogen"
With a double bond (=unsaturated fats), each carbon has just one hydrogen attached. A double is quite reactive.
Transforming unsaturated into saturated (trans fats)
The food business takes advantage of unsaturated fats' reactiveness. Unsaturated lipids are converted to saturated fats by a process known as hydrogenation (see below). It has the effect of solidifying the oils, converting olive oil, for example, into margarine.
This is an unhealthy fat source that should be avoided; these are the infamous trans-fats (responsible for poor cholesterol balance) that have been connected to the core cause of many cardiovascular disorders. These fats do not exist in nature, and our bodies are not designed to handle them all correctly.
Look out for the term "hydrogenated oil" in the ingredient lists of your favorite processed food : frozen pizza, vegetable oil mix, health/weight-loss food, baked goods, chips or ice-cream.
Their usage in food is problematic because they directly contribute to the formation of harmful cholesterols in our blood vessels, but in cosmetics...shouldn't be an issue, right?
It isn't, at least not for the skin; the issue stems more from the manufacturing process, giving it a low score in terms of sustainability. Instead of employing better ingredients from the start, unnecessary processes are taken. Certainly, industrial expenses are being reduced, and the product is less expensive to purchase, but the health of the (uninformed) consumer is at stake here.
To hydrogenate an oil, extra energy is required, and it must be treated at very high pressure, with dihydrogen moving through the oil along with tasty heavy metals such as nickel or palladium. Heavy metals are utilized as catalysts in the reaction (to increase its efficiency) and should not be found in the final product.
Sources
Hooper L, Martin N, Jimoh OF, Kirk C, Foster E, Abdelhamid AS. Reduction in saturated fat intake for cardiovascular disease. Cochrane Database Syst Rev. 2020
European guidelines on cardiovascular disease prevention in clinical practice: executive summary: Fourth Joint Task Force of the European Society of Cardiology and Other Societies on Cardiovascular Disease Prevention in Clinical Practice (Constituted by representatives of nine societies and by invited experts), European Heart Journal, Volume 28, Issue 19, October 2007, Pages 2375–2414
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