Margarine Isn’t Plastic
Claim
Margarine is one molecule away from plastic.
Truth
A surprisingly pervasive chemistry myth has been popping up for over two decades now. The unsourced claim is typically that margarine is “one molecule away from plastic” or “one molecule away from formaldyhyde”. It is not clear where this false claim originated, but it often pops up on social media or by self-proclaimed “nutritionists.” Recently, British celebrity chef James Martin repeated the falsehood as “two elements away from plastic.”
Margarine is not one substance. It is a mixture of water and various fatty acids (colloquially called “fats” or “oils”), held together by emulsifiers like lecithin. The most chemically-similar substance in margarine to plastics is definitely the fatty acids, so to take this claim in the most forgiving light, we will assume those are what it is talking about, rather than margarine as a whole.
The most common fatty acids in margarine are palmitic acid, linoleic acid, oleic acid, and stearic acid. These are all naturally-occurring fatty acids present in most botanical seeds, which is where margarine gets them from. Historically many of the oils were hydrogenated, but since the harms of trans fats were discovered, this is no longer done in developed countries. Being fatty acids, they are all hydrocarbon chains with a carboxyl group (–COOH) at one end and a methyl group (–CH3) at the other. You can see these four below:
Some are more bendy than others and missing a few hydrogens, but they all are very similar and fairly simple. They are just long carbon chains with hydrogen atoms filling most of the bonds and with carboxyl groups at the end. Some double-bonds at different locations, making them bendier, but they are all very chemically similar. They are also all fixed lengths. All of them have 18 carbon atoms except palmatic acid, which has 16. If you change the length or anything about the structure, you no longer have the same chemical.
To get a pat of margarine, you combine roughly two million of these fatty acid molecules, about a quarter as much water, and a a tiny bit of emulsifier. The fatty acids are not chemically bonded to each other, but they are held together by the emulsifier. The emulsifier is a molecule with a hydrophilic (water-loving) end and a hydrophobic (water-hating) end. The hydrophilic end sticks to the water, and the hydrophobic end sticks to the fatty acids. This holds the fatty acids in suspension in the water, and the result is a spreadable mixture.
Plastics on the other hand typically are one substance, but there are many different types. Even within the same type of plastic, they are polymeric macromolecules and thus defeat the ability to write specific formulas for them. Such polymers are completely unlike any natural polymers, let alone fatty acids. They are at least tens of thousands of times larger.
Below is an attempted visualization of a potential very small section of polyethylene, a common plastic which is superficially the closest to fatty acids:
At first glance, this sort of looks like a fatty acid. It comprises primarily a long carbon chain. However, it is very different.
First, it does not have the carboxyl group on the end. What may seem a minor change often has a radical change in chemistry. Removing the carboxyl group from valeric acid, a fatty acid naturally produced by your gut, creates lighter fluid. Adding a single oxygen atom to table salt creates chlorine bleach. Even a single atom difference is often enough to make a huge difference in chemistry.
Second is the size. Again, each fatty acid is strictly defined by its length. This one is 16 carbons long, this one is 18 carbons long, this one has a double bond at atom #9, etc. If you change one thing, it’s not the same chemical. Plastics do not just change one thing either. They add hundreds of thousands of monomers together. The above is just a tiny, tiny section of a polyethylene molecule, which branches all over. This makes it radically different from fatty acids. If you were to shorten it and strip it down to its base monomer, you would have ethylene, which is an important gas fruits produce to ripen. The length and branching of polyethylene is what makes it a plastic, not the monomer.
Furthermore, because of its simple structure, polyethylene is not very reactive. Clean Production Action named polyethylene one of the most benign plastics. Rather than the carbon chain being a sign of danger, it makes it such a safe chemical that even plastics made from it are used to store food. Carbon chains are the fundamental unit in organic chemistry and therefore the basis of all life. There is nothing dangerous about it.
Butter
Typically this claim is used to support eating butter as more natural and healthy than margarine. However, butter is also a mixture of triglycerides, water, and emulsifiers. Triglycerides are glycerol with three fatty acids attached. The fatty acids in butter’s triglycerides are primarily…palmitic acid, oleic acid, myristic acid, and stearic acid. These are the same fatty acids as in margarine. Below are the two most common triglycerides in butter:
As you can see, this is practically the same thing as margarine. While, again, neither is at all similar to plastic, this even looks more superficially like it. Rather than being “one molecule away from plastic,” margarine is one molecule away from butter.
There is nothing chemically dangerous about either margarine or butter. The only real dangers from either are the calories and cardiovascular issues caused by overconsumption of saturated fats. For this reason, Mayo Clinic recommends modern margarine as a healthier alternative to butter for its higher proportion of unsaturated fats. Rather than listen to fear-mongering on the Internet, listen to your doctor about their dietary recommendations.
Paint Ingredients
Often this claim is also bundled with the similarly nonsense claim that it “shares 27 ingredients with paint.” Again, no explanation is attached of what these shared ingredients are or how they are harmful, likely because the idea is made up out of thin air. There’s no definitive list of ingredients for either substance, but margarine is primarily just a variety of fatty acids mixed with water and emulsifiers like lecithin or diglycerides. Often some table salt will be added. Paint is a more complex mixture of solvents, binders, and pigments. The solvents are typically water and glycols, the binders are commonly styrene-acrylic polymers, and the pigments are extremely various; but they are surely not in your margarine. If they were, you would doubtless notice the corresponding neon color. So there is actually only one ingredient shared between margarine and paint: water. If you want to avoid that ingredient, that is your choice, but it is not a very practical one.