Some people say that if fish oil can melt or dissolve styrofoam, that means it is "bad" fish oil. Here is an example video of someone making that claim.
Does fish oil's ability to dissolve styrofoam reflect its quality?
In short, the claim that the TG form is, in any clinically significant way, more advantageous or beneficial than the EE form is not supported by credible science at this time. In fact, the EE form has been used in the majority of cardiovascular-related clinical trials showing benefit of omega-3s, and is the choice for the National Eye Institute’s AREDS 2 trial now in progress. The EE form enjoys a strong safety profile when taken as directed, and a more highly concentrated, prescription EE product is approved by the FDA. Source: Science based health
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. Source: Honest Nutrition
Polystyrene (Styrofoam®) dissolves in some types of fatty acids including fish oils.
In fact, the answer is simple, if rather boring: – By its nature, polystyrene dissolves in some long chain fatty acids found in natural fats and oils. This is not even a chemical reaction: just like sugar dissolves in water, polystyrene happens to dissolve in some types of fatty acids. And highly purified concentrated Omega-3 fish oils are one of the things that dissolve polystyrene. Source: USANA