Dr. Dryberg and his Danish co-workers report that the availability of omega -3’s in the Triglyceride form was significantly higher than omega-3’s in the Ethyl ester form, according to new findings published in the form of Prostaglandins, Leukotrienes and Essential Fatty Acids. The blinded, placebo controlled study involved 72 people aged between 21 and 26.
Participants received a daily supplement of one form of omega 3 – daily doses of EPA plus DHA between 3.1 gm and 3.6gm for two weeks. At the end of the intervention, the researchers report that “the mean relative bioavailability of EPA plus DHA from Ethyl ester was 73% v. 124% for Triglyceride which demonstrates a 70% increased absorption for the triglyceride form over the ethyl ester form.
“Our results demonstrate that bioavailability may differ between the commonly used types of concentrated fish oil preparations. Re-esterified triglycerides have superior bioavailability, whereas ethyl esters may have a lower bioavailability.”
Wrote researchers from the University of Copenhagen and Aalborg Hospital.
In fish, the omega-3 fatty acids, EPA and DHA, occur naturally in triglyceride form. To make a quality fish oil concentrate, the individual fatty acids must first be removed from the glycerol backbone. To stabilize these delicate fatty acids, they are bound to an ethyl alcohol molecule before they undergo molecular distillation to both purify and to increase the amounts of EPA and DHA.
Once the desired concentration is achieved, a manufacturer chooses from two distinctly different options. The first is to reattach the fatty acids to the glycerol backbone in a process known as “re-esterification” to recreate the natural triglyceride structure. The second, far less costly option is to leave the fish oil as an ethyl ester, a “new to nature” form of fatty acid.
According to Nordic Naturals CEO Joar Opheim,
“It is great to see science proving what we at Nordic Naturals have always believed. Our understanding of the body’s utilization of ingested omega-3s has always supported our commitment to re-esterified triglycerides as the best form for our concentrated fish oils”.
CLINICAL STUDIES ON BIOAVAILABILITY
Previous to the recent study, six human trials have compared the absorption of ethyl ester (EE) and Triglyceride (TG) fish oil supplements. Of the six studies, four concluded that the TG form absorbs better, and the other two studies did not find a significant difference in absorption.
Dietary fish oil is digested in the small intestine by the emulsifying action of bile salts and the hydrolytic activity of pancreatic lipase. The hydrolysis of a triglyceride (TG) molecule produces two free fatty acids (FFA) and a monoglyceride (one fatty acid combined to glycerol). These metabolic products are then absorbed by intestinal enterocytes and reassembled again as TGs. Carrier molecules called chylomicrons then transport the TGs into the lymphatic channel and finally into the blood.
The digestion of EE fish oils is slightly different due to the lack of a glycerol backbone. In the small intestine it is again the pancreatic lipase that hydrolyzes the fatty acids from the ethanol backbone however the fatty acid-ethanol bond is up to 50x more resistant to pancreatic lipase as compared to hydrolysis of TGs. The EEs that get hydrolyzed produce free fatty acids plus ethanol. The FFA’s are taken up by the enterocytes and must be reconverted to TGs to be transported in the blood. The TG form of fish oil contains its own monoglyceride substrate, where as EE fish oils, coupled to ethanol, do not. EE must therefore obtain a monoglyceride substrate from another source. Without a glycerol or monoglyceride substrate TG re-synthesis is delayed, suggesting that transport to the blood is more efficient in natural TG fish oils in comparison to EEs. Furthermore, this delay of TG re-synthesis in EE fish oils could cause an increase in free fatty acids and subsequent oxidation of those free fatty acids.
STABILITY OF ETHYL ESTERS V. TRIGLYCERIDES
EPA and DHA are long-chain polyunsaturated fats (PUFA’s) which means they contain several double bonds within their carbon-hydrogen chain. In each location of a double bond, there is vulnerability for free radical attack, which results in an oxidised and rancid oil. The inherent structure of three fatty acids attached to one glycerol backbone in the TG form provides protection to the double bonds in the long-chain PUFA’s from being exposed to free radicals. An ethyl ester fatty acid, on the other hand, exists as a single strand, and is exposed on all sides to free radicals. This basic biochemistry suggests the superior stability of TG fish oils both inside a capsule or liquid as well as within the body. Ethyl ester fish oils are less stable, and readily oxidize. Resistance to oxidative damage is a critical quality of a fish oil supplement as a fish oil that has been subject to oxidative damage may do more harm than good.
Current research points toward the triglyceride form for better absorption and assimilation.