Omega-3 bioavailability: Scientists lift the lid on which forms work best

By Stephen Daniells

- Last updated on GMT

Related tags: Fatty acids, Omega-3 fatty acid, Fatty acid

Omega-3 fatty acids in the re-esterified triglyceride form may be the most bioavailable, according to a new study by omega-3 pioneer Jorn Dyerberg.

Dr Dyerberg and his Danish co-workers report that the bioavailability of omega-3s in the re-esterified triglyceride was 50 percent higher than omega-3 in the form of free fatty acids or ethyl esters, according to new findings published in Prostaglandins, Leukotrienes and Essential Fatty Acids​.

“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. Free fatty acids have medium bioavailability, which is not different from that of natural fish oil triglycerides,”​ wrote researchers from the University of Copenhagen and Aalborg Hospital.

Heart health and beyond

The heart health benefits of consuming oily fish, and the omega-3 fatty acids they contain, are well-documented, being first reported in the early 1970s by Dr Dyerberg and his co-workers in The Lancet​ and The American Journal of Clinical Nutrition​. To date, the polyunsaturated fatty acids (PUFAs) have been linked to improvements in blood lipid levels, a reduced tendency of thrombosis, blood pressure and heart rate improvements, and improved vascular function.

Beyond heart health, omega-3 fatty acids, most notably EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid), have been linked to a wide-range of health benefits, including reduced risk of certain cancers, good development of a baby during pregnancy, joint health, and improved behaviour and mood.

Despite such benefits there are still problems with ensuring adequate omega-3 intakes from fatty fish. This has led to a fleet of omega-3-rich concentrates becoming available. Projections by Frost & Sullivan set annual growth for the omega-3 market at an impressive 24 per cent, and the market is estimated to be worth $1.6bn by 2014.

Various forms of concentrated omega-3 fatty acids are available on the market, and these include free fatty acids (FFA), ethyl esters (EE) or as re-esterified triglycerides (rTG). The latter term refers to products made from fish body oil, “in which the approximate 30 percent TG content is transferred to ethyl esters and then molecularly distilled to remove the short chain and the saturated fatty acids increasing the EPA and DHA contents to around 60 percent”,​ explain the researchers.

According to Dr Dyerberg and his co-workers, questions still remain as to the actual bioavailability of EPA and DHA from the various omega-3 formulations, and so they set out to test the availability of five commercially available fish oil supplements - natural TG in fish body oil, cod liver oil, EE, FFA and rTG. The blinded, placebo-controlled study involved 72 people aged between 21 and 56.

Participants received a daily supplement of one form of omega-3 (daily doses of EPA plus DHA between 3.1 and 3.6g) for two weeks.

Comparing the formulations

At the end of the intervention the researchers report that “the mean relative bioavailability of EPA plus DHA from EE was 73 percent, from FFA 91 percent and from rTG 124 percent. Adjusted for dosage, the results were 76, 86 and 134 percent, respectively”​.

“Interestingly, we found an even higher index of bioavailability (124 percent) of rTG than of natural TG (fish body oil and cod liver oil), although it should be stressed that this difference was only significant when compared with cod liver oil. A tentative explanation for this finding could be that besides TG, rTG also contains both diglycerides and monoglycerides,”​ explained the researchers.

“It should, however, be stressed that these conclusions are based on a relatively short-term (two-week) study at a fixed daily omega-3 fatty acid dose of approximately 3.5g; it cannot be ignored, even if it seems unlikely that a different period of supplementation or a different dose may have led to different results,”​ concluded Dr Dyerberg and his co-workers.

The rTG, EE, FFA, and FBO supplements were all sourced from EPAX.

Source: Prostaglandins, Leukotrienes and Essential Fatty Acids
September 2010, Volume 83, Issue 3, Pages 137-141
“Bioavailability of marine n-3 fatty acid formulations Original Research Article”
Authors: J. Dyerberg, P. Madsen, J.M. Møller, I. Aardestrup, E.B. Schmidt

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