Do You Know Your Omega 3s?
by: John Romano
In my last article I defined the role Omega-3 fats play and eluded to its various forms. This article will discuss what those forms are and how the body deals with them.
When it comes to “fish oil” and “Omega-3” supplements, the subject of fats and the fatty acids they contain can be a confusing topic. There are several forms of the Omega-3 fats EPA and DHA found in fish oil that we consume in our diets and in our supplements, all of which require certain processes in order for the body to utilize them. And, as with all things in life, some are better (more bioavailable in this case) than others. Below is a very simplified rundown of the various forms of Omega-3 fats we consume and how the body converts the fatty acids they contain into the bioavailable fractions the body can utilize, and which can be utilized best.
Free fatty acids are the building blocks of all fats. They are long chain fatty acids that are either saturated or unsaturated and not attached to other molecules, hence the term “free.” In nature, free fatty acids are bound to other molecules to form triglycerides or phospholipids present in animal tissue (meat). During the digestion process, free fatty acids (either from food or supplements) must be liberated from other molecules to which they may be bound by various enzymes in order to pass through the intestinal wall. Only free fatty acids and mono glycerides can cross the intestinal membrane and into the blood stream. Free fatty acids are the most usable form of fat, and they yield the most energy in the form of ATP.
Triglycerides are made up of three free fatty acids bound to one glycerol molecule. This is the structure of all fats in nature such as the Omega-3 fatty acids EPA and DHA found in fish (and fish oil supplements). Omega-3s in triglyceride form are composed of either one EPA molecule (eicosapentaenoic acid) or one DHA molecule (docosahexaenoic acid) and two other fatty acids, bound to a single glycerol backbone. This means that, on average, the Omega-3 content (EPA + DHA) of fish oil never exceeds 33%, and the other 67% consists of other fatty acids.
Phospholipids are similar to triglycerides in that they contain glycerol and fatty acids. Phospholipids, however, are a much more complex structure having two fatty acids bound to a glycerol molecule “head” and two at its “tail” with a third bound molecule that contains a component known as a phosphate. Phospholipids are found in every cell in the body, as they are part of the cell membrane, which surrounds all cells. The cell membrane is made up of a double layer of phospholipids as well as other molecules, such as proteins and cholesterol.
Ethyl esters are made in the lab from Omega-3 fatty acids that were once triglycerides. They are made by chemically separating the three fatty acids from the glycerol molecule using ethanol (pure alcohol). The reaction results in a new ester compound consisting of the former free fatty acids bound (“esterified”) to ethanol resulting in “omega-3 ethyl ester.” Because esterification separates the individual free fatty acids (EPA, DHA and the other non-Omega-3 fatty acids), it makes it possible to concentrate the EPA and DHA components to produce 50%-90% pure EPA or DHA.
Once ingested, the digestive process and subsequent absorption of fatty acids varies from one group to the next.
In order for both triglycerides and ethyl esters to pass through the intestinal wall and into the bloodstream, these fats first have to be digested in the gut by enzymes such as lipase and hydrolase. The interaction with these enzymes breaks down (cleaves) either the glycerol or ethanol backbone binding the fatty acids producing free fatty acids and monoglycerides (glycerol molecules with 1 bound fatty acid).
Phospholipids are acted upon by the enzyme phospholipase and broken down into glycerol, free fatty acids, phosphoric acid, and other compounds such as choline. These simplified compounds are then able to pass through the intestinal wall and into the blood stream.
These processes are not 100% efficient. Digestive acids in the stomach can destroy some of the Omega-3s and the cleaving of the ethanol or glycerol backbone can also damage some Omega-3s. Free fatty acids on the other hand, bypass the breakdown process because they are already in free form and available to be absorbed when ingested.
Once the mono glycerides and free fatty acids pass through the intestinal wall they are recombined into either triglycerides or phospholipids and then bound to cholesterol forming new compounded fats called chylomicrons. During this last phase of absorption, the intestinal cells give the new fats a special coating so that they are readily transported in the bloodstream. Once they have arrived in the bloodstream they are transported to various body tissues where they are utilized.
How well is each form utilized? That will be the subject on the next installment when we discuss bioavailability of Omega-3s. The answer might surprise you…