Fish Oils: Ethyl Ester versus Triglyceride forms

Low strength natural fish oils are in triglyceride (TG) form, as are most natural oils. To purify the oils by removing impurities and less desirable fatty acids and to concentrate the EPA and DHA fatty acid components, molecular distillation is used.  This process allows the oil to vaporize at low temperatures under pressure and is also known as vacuum distillation. The resulting vapor is collected and cooled, stratifying into distinct layers of fatty acids. This allows a purer esterified oil (called an ethyl ester form, or EE) with higher levels of EPA-DHA than crude fish oils and removal of triglycerides and cholesterol as well as other undesirable components. 

Some companies like to add triglycerides back in; this dilutes the fish oil concentrate by about 20% and the process also introduces mono- and di-glycerides, which don’t exist in natural fish oils to a significant degree but are thought responsible for higher absorption levels of this reconverted triglyceride form (rTG) oil over natural triglyceride and ethyl ester forms. If no triglycerides are added back, the body’s own store of triglycerides will be used to bond to the fatty acids after absorption, potentially lowering serum triglycerides more than an rTG oil. 

Absorption from our guts is always in the form of free fatty acids, so the oil’s original triglycerides are typically discarded during digestion and reattached later from body stores. This lowers the potential of the TG or rTG oils to lower triglycerides already in our bodies since they introduce additional triglycerides, which may be absorbed either into the body (adding more triglycerides into the liver) or into fiber or other materials that carry cholesterol out through the stool (potentially reducing the removal of cholesterol by competitive absorption). 

The prescription fish oils are in the ethyl ester form, not triglyceride form, because of the higher purity and higher strength of EE fish oils over TG or rTG forms resulting in better study outcomes on cardiovascular health measures. 

Krill oil is distinct because of its phospholipid matrix that greatly enhances omega-3 absorption more than the EE, TG, or rTG forms of fish oil.

Fish Oil: Excerpts from a magazine interview with me

The balance of fatty acids in the body can promote inflammatory or non-inflammatory states. Higher amounts of omega-3 fats in the diet have been shown to modulate inflammation and keep it within healthy ranges. The various cellular and tissue damage that can occur from chronic inflammatory states are certainly not healthful. This basic mechanism of action implies a wide-ranging and powerful effect of omega-3 fats to support wellness. Additionally, these fats are part of brain and nerve structures, so they help to maintain the health of those tissues, as well.

Omega-3 and omega-6 fats have been called “essential fatty acids” since the body can’t manufacture them from other fats, as it typically can for other types of fat. The optimal ratio of omega-6 to omega-3 fats is somewhere between 1:1 and 3:1. The common American diet has been estimated to be over 15:1, a marked deviation from a healthy norm.

The benefits of most other non-omega-3 fatty acids in fish oil are not well-defined in the scientific literature. Fish oil naturally contains a range of fats, including cholesterol, triglycerides, and stearic acid. The ones that are considered less desirable, cholesterol and triglycerides, are sometimes removed from fish oils to further concentrate the omega-3 portion and allow higher strengths in fewer capsules.

All natural oils contain various mixtures of fatty acids in varying amounts. Omega-9 fats are best known as being abundant in Olive Oil, and are considered non-inflammatory and especially healthy if substituted for most omega-6 fats that are pro-inflammatory. Some natural oils are fairly well balanced, such as flax and hemp seed oils, or walnut oil. Others, like fish oil, tend to be predominantly omega-3. Most vegetable oils are mostly omega-6 fats and their predominance in the modern diet has been blamed for some of our poor health.

Some consumers do know about various sources of fish oil, and some have advantages or disadvantages. For example salmon is a favored source of omega-3 fats, though salmon oil typically contains less than other common fish oils. Traditional fish sources may be better accepted by those who won’t or can’t eat shellfish. The fisheries in Norway and Peru are among the best managed traditional fisheries on earth.

Krill, a small crustacean shellfish, is a unique source of omega-3 fats since krill also naturally bonds the fatty acids to phospholipids, which are essential for cell membranes and which enhance the bioavailability of the oil. Krill oil also contains the powerful antioxidant pigment astaxanthin, which is responsible for the color of shrimp and salmon. Krill is considered the best managed fishery in the world, with trained observers on each boat monitoring the harvest. The krill harvest limit can be rapidly adjusted to support a healthy population, and the total world harvest (most of which goes into pet foods) is only a fraction of the allowable sustainable harvest level.