Margarine and plastic are chemically unrelated substances, contrary to persistent online claim

In November 2024, the claim “margarine is one molecule away from plastic” circulated on Facebook and Instagram. One instance posted on Facebook was shared more than 60,000 times. The account that published this post was @thebaconexperiment, which has over 100,000 followers.

The claim has been circulating online since at least 2003, resurfacing occasionally on different social media platforms, sometimes boosted by otherwise credible media.

The gist of the claim is that margarine is essentially plastic, and therefore unnatural or “bad”. This interpretation is made clear in one comment from the author of the Facebook post, stating “Vegans love seed oils but in no way whatsoever are they ‘healthy’ in any way. Quite the opposite, it’s no bacon(sic) that “clogs arteries” it’s this garbage in my opinion”.

However, this is incorrect in multiple ways and reflects a complete misunderstanding of the basic principles of chemistry. We explain why below.

Margarine and plastics: what are they?

Before going any further, we first need to start with some basic concepts in chemistry.

All matter is made of atoms, which are the basic building blocks of chemistry. When two or more atoms form chemical bonds with each other, they form a molecule. Molecules can be made of just one element, like hydrogen molecules (H₂), but they can also be compounds if they contain two or more elements combined in a fixed ratio. Water (H₂O) is one example of a molecule that is also a compound. Finally, substances formed by two or more elements or compounds that aren’t chemically bound are called mixtures.

Margarine is a complex mixture of animal or vegetable fats and water. In addition, it contains small amounts of other ingredients, such as emulsifiers, salt, lecithin, pigments, and vitamins. There are many types of margarine whose chemical composition depends on the source of fat they use.

In contrast, plastics are extremely long synthetic chains of repeating units. Like margarine, there are also many different types of plastic, which vary greatly in their composition and properties.

From these definitions we can already see that margarine and plastics differ in their composition and structure and are therefore two different substances. While both contain hydrogen and carbon atoms, margarine also contains oxygen, which is absent in plastic.

Margarine and plastic are chemically very different

Margarine was invented by French chemist Hippolyte Mège-Mouriès in 1869, after the French Emperor Napoleon III offered a price to the person who developed a lower-priced substitute for butter. The product, called oleomargarine, was made from beef tallow and soon achieved international popularity.

However, margarine’s composition has varied widely since. By the 1950s, most manufacturers had replaced the animal fats used in oleomargarine with vegetable oils. These are also the predominant fats used in current forms of margarine, which commonly include oils from canola, safflower, sunflower, corn, soybean, and more recently, palm.

Current forms of margarine are a blend of animal or vegetable oils and water or skimmed milk. Therefore, when we talk about margarine, we are referring to a very complex mixture whose composition varies greatly depending on the brand^[1].

Let’s assume that the claim referred exclusively to the more common vegetable margarine, whose main component is the vegetable oils it is made of.

Vegetable oils are mainly composed of triglycerides, a naturally occurring type of fat consisting of one molecule of the alcohol glycerol (also called glycerin) bound to three molecules of fatty acids that can be identical or different.

Fatty acids are the building blocks of fats, and each type of vegetable oil contains different types and amounts of fatty acids. The most common fatty acids in margarine include oleic acid, linoleic acid, stearic acid, and palmitic acid. These fatty acids all have the same backbone structure, consisting of a chain of 18 carbon atoms (except palmitic acid, which has 16) bound to a carboxyl group (-COOH) (Figure 1).

Figure 1 – Structural formula of stearic acid, a fatty acid containing 18 carbon atoms. Each carbon atom is bonded with two hydrogens (-CH₂); the last one forms part of the carboxyl group (-COOH). Image generated with the McGraw Hill Education online simulator on the American Chemistry Society website.

Plastics, on the other hand, aren’t mixtures but extremely long synthetic chains of repeating molecules (polymers). Polyethylene is the most simple plastic polymer because it contains only one kind of molecule, ethylene. This molecule is made of carbon and hydrogen atoms (C₂H₄) that repeat thousands of times to form long chains (Figure 2).

Figure 2 – Structural formula of the polymer polyethylene, formed by repeating units (monomers) of ethylene. The red lines on both ends indicate that the repetitions continue. Source: Michigan State University.

While this structure may look similar to that of fatty acids, it’s not. First, because polyethylene doesn’t have the carboxyl group that fatty acids have on one end. Second, because the carbon chain in polyethylene is thousands of times longer than that of fatty acids and can also have side branches. Also, it is important to remember that margarine contains other ingredients besides fatty acids.

Based on its composition, the truth is that margarine is much closer to butter, which is also made of fatty acids, than it is to plastic.

Even small variations in chemical composition can result in entirely different substances

The main problem with the claim that “margarine is one molecule away from plastic” is that it disregards the huge difference that one single molecule can make on the chemical properties of a substance.

What determines the properties of a substance is its elemental composition and how elements are arranged within that substance.

For example, adding or subtracting one single atom from a compound can greatly impact its properties. Adding one atom of oxygen to water (H₂O) results in hydrogen peroxide (H₂O₂). But while water is a harmless compound that you can drink or bathe in, hydrogen peroxide is a hazardous substance with bleaching effects that is toxic when inhaled and ingested, even at relatively low concentrations.

This example clearly illustrates how very similar chemical compositions can result in entirely different substances.

Earlier margarine contained harmful trans fats that aren’t present in current margarine

A high intake of earlier forms of vegetable margarine was associated with cardiovascular problems^[2,3]. But contrary to the claim, this had nothing to do with how chemically similar margarine is to plastic, but with a specific step in the manufacturing process.

Butter and other animal fats are solid at room temperature because they are mainly composed of saturated fats. Because saturated fats contain cholesterol, they can increase the risk of heart disease if consumed in excess.

In contrast, vegetable oils are rich in unsaturated fats, which are considered beneficial and are associated with improved cardiovascular health. But vegetable oils are liquid at room temperature. To convert them into a spreadable product, traditional manufacturing used a chemical reaction called hydrogenation.

As Science Feedback explained in an earlier review, hydrogenation generated high levels of trans fats as a byproduct. In the 1990s, researchers found that trans fats raise cholesterol levels even more than saturated fats, and people who consumed partially hydrogenated oils had a significantly increased risk of heart disease and stroke^[3,4].

These findings led the U.S. Food and Drug Administration to change its classification of trans fats to no longer generally recognized as safe (GRAS) in 2015. In December 2023, the FDA made effective a new rule that revoked the use of partially hydrogenated oils in the most common food products.

But current margarine is produced using a different solidification process called interesterification. This new process results in a product with less saturated fat and cholesterol than butter and no artificial trans fats. For this reason, current forms of margarine are considered healthier than butter.

Conclusion

The claim that “margarine is one molecule away from plastic” is incorrect in several ways. Two substances that differ in only one molecule are still different and can have completely different properties. But margarine and plastic differ in much more than one molecule. Margarine is a very complex mixture, and it would be impossible to turn it into plastic by simply adding or removing one molecule.

Vegetable oils in earlier margarine used a solidification process that generated harmful trans fats as a byproduct. These trans fats, not the actual ingredients in margarine, are associated with heart problems. However, current manufacturing processes involve a different solidification method that doesn’t generate trans fats. There is nothing intrinsically harmful in the chemical composition of current margarine, other than the calories that any fat contains, which can cause weight gain if consumed in excess.

REFERENCES

• 1 – Garsetti et al. (2016) Fat composition of vegetable oil spreads and margarines in the USA in 2013: a national marketplace analysis. International Journal of Food Sciences and Nutrition.
• 2 – Willett et al. (1993) Intake of trans fatty acids and risk of coronary heart disease among women. The Lancet.
• 3 – Gillman et al. (1997) Margarine intake and subsequent coronary heart disease in men. Epidemiology.
• 4 – Mensink et al. (1990) Effect of Dietary trans Fatty Acids on High-Density and Low-Density Lipoprotein Cholesterol Levels in Healthy Subjects. New England Journal of Medicine.