Recent attention given to the effects of various fish oils on polystyrene (Styrofoam®) cups has led to some misunderstanding of how these products work in terms of nutrition and safety. It is unfortunate that the use of these stunts imply may confuse or even scare people away from taking this natural product which provides constituents that are essential to human health. Don’t be fooled by this trick! If someone tries to use it as a means to push one product over another, challenge them to explain exactly what the test is supposed to mean. Here’s what you need to know about the test, how it works, and what it means:
Styrofoam® (polystyrene) cups can be dissolved by pure fish oils. All fish oils will have this same effect on polystyrene, but some will take much longer than others. Various healthy natural substances, like fresh lemon oil, will also dissolve polystyrene. In the Styrofoam® cup test, the esterified ethyl ester form of fish oil works to dissolve Styrofoam® much faster than the triglyceride form simply because the number of chemical bonds in the two forms of oil are different; with ethyl ester fish oil having its number of bonds closer to that of Styrofoam®. This similar chemical polarity is the same reason why pure lemon oil also works quickly to dissolve Styrofoam®. No solvents are used to produce the fish oils, so none are present in the finished products. This magic trick does not translate into any legitimate safety concerns, despite its obvious visual impact. Fortunately, the human body is not composed of polystyrene and is not negatively affected by fish oils in its commonly available forms.
Fish oil naturally comes in a volatile triglyceride (triacylglycerol) form and can be esterified for additional benefits. As soon as a fish is caught the oils begin to degrade and can easily go rancid. Esterification is a process that stabilizes and maintains the freshness of fish oil to prevent rancidity and allows higher concentrations of the essential omega-3 EPA and DHA fatty acids to be available. During this esterification process, the triglycerides are removed, changing the number of molecular bonds in the fish oil. Both the purified ethyl ester form and the triglyceride form must be digested to a simpler fraction, the free fatty acid, to allow bioavailability from the human gut. Ethyl ester and triglyceride forms are equally well digested by lipase and available for absorption as free fatty acids, and the ethyl ester form is at least as bioavailable as the triglyceride form. (1)
There is some evidence that the ethyl ester form will sustain circulating levels of the omega-3 fatty acids EPA and DHA better than the triglyceride form. The ethyl ester form of EPA and DHA is the form that is used in most successful clinical studies evaluating the potential health benefits of supplemental Omega-3 fats. In fact, clinical trials on the ethyl ester form more consistently generate positive results than those done with the triglyceride form. Also EPA and DHA as ethyl esters inhibit platelet aggregability and control serum triglycerides while leaving other serum lipids essentially unaltered. (2) The ethyl ester forms build up body stores, allowing conversion to free fatty acids more consistently than the triglyceride form. (3) Because of their proven benefits and safety, it would be unfortunate if a misunderstood “test” causes some people to reject the use of solvent-free ethyl ester fish oils as part of their diet.
Chemical Polarity plays a role in how compounds react with one another. Polarity refers to the electro-magnetic charges of a molecule, or the attraction between the positively and negatively charged parts of a molecule. Compounds are considered polar due to the unequal sharing or electrons. For example, water is a polar compound. A compound is non-polar when the electric charge is balanced. Edible oils are typically non-polar.
In Chemistry there is a rule to describe how polar and non-polar solvents react with similar solutes: “like dissolves like”. We all know that oil and water do not mix. The reason why is that water, which is polar, will not react (mix) with oil, which is non-polar. “Like dissolves like.”
Two common compounds, sugar and salt, are both polar and in nature they readily mix with water, another polar compound.
With polarity, compounds of differing polarity do not react/mix, while those with like polarity do mix. So a chemical reaction occurs when a non-polar compound comes into contact with another non-polar compound, and more readily when the number of chemical bonds in one substance more closely matches the other.
Polystyrene, a moisture-resistant foam commonly known as Styrofoam®, is formed from a long chain of polymers. This plastic is used in the manufacture of coffee cups and plates as an insulator and as packaging material, and is non-polar. What makes Styrofoam® ideal for keeping most hot beverages hot and cold beverages cold is that as a non-polar compound it will not react with the polar water used to make coffee, tea, and other beverages. This same material will react with any form of edible oil; this can be olive oil, lemon oil, fish oil, etc. This reaction is naturally occurring and its intensity is based solely upon the chemical properties of both compounds and the polarity of each.
All edible oils, which like Styrofoam® are non-polar, are made up of fatty acids; and these fatty acids are made up of a long chain of hydrocarbon molecules. With Fish Oils, some contain triglycerides and some contain ethyl esters. Both the triglyceride form and the ethyl ester form first need to be digested and broken down to a free fatty acid for absorption from the GI tract. After uptake, the free fatty acid is then converted to a triglyceride form in the liver by the addition of already available triglycerides obtained from circulating lipids (fats).
In the example of fish oils, ALL will react with Styrofoam over time; the length of time is determined by the number of chemical bonds in each type of fish oil relevant to the number of chemical bonds in Styrofoam®. Triglycerides will take longer to react with the cup, while oils bonded to ethyl esters, which have more chemical bonds, will naturally penetrate the cup wall faster.
- Krokan HE, Bjerve KS, Mørk E. The enteral bioavailability of eicosapentaenoic acid and docosahexaenoic acid is as good from ethyl esters as from glyceryl esters in spite of lower hydrolytic rates by pancreatic lipase in vitro. Biochim Biophys Acta. 1993 May 20;1168(1):59-67. PMID: 8504143
- von Schacky C. A review of omega-3 ethyl esters for cardiovascular prevention and treatment of increased blood triglyceride levels. Vasc Health Risk Manag. 2006;2(3):251-62. Review. PMID: 17326331
- Rupp H, et al. Risk stratification by the "EPA+DHA level" and the "EPA/AA ratio" focus on anti-inflammatory and antiarrhythmogenic effects of long-chain omega-3 fatty acids. Herz. 2004 Nov;29(7):673-85. Review. Erratum in: Herz. 2004 Dec;29(8):805. PMID: 15580322