Concentrated fish oil (esterized) is bad business! Fatty acid ethyl esters are lipids that are made by reacting free fatty acids with ethanol in a chemical process called trans-esterification. Here the glycerol backbone is removed and substituted with ethanol to “concentrate” the long chain fatty acids at lower temperatures. The resulting EPA and DHA concentrate is subsequently marketed as “Fish Oil concentrate” but in reality the EPA and DHA ethyl ester concentrate is no longer a fat or oil and is incorrectly marketed as fish oil. Ethyl esters almost never occur in nature and most certainly affect the way EFAs are digested and absorbed in the body.