If you have a choice, the triglyceride form of fish oil is preferable. The triglyceride form, i.e., 3 omega-3 fatty acids on a glycerol "backbone," is the form found in the body of fish that protects them from cold temperatures (i.e., they remain liquid at low ambient temperatures).
Most fish oils on the market are the ethyl ester form. This means that the omega-3 fatty acids have been removed from the glycerol backbone; the fatty acids are then reacted with ethanol to form the ethyl ester.
If the form is not specified on your fish oil bottle, it is likely ethyl ester, since the triglyceride form is more costly to process and most manufacturers therefore boast about it. Also, prescription Lovaza--nearly 20 times more costly than the most expensive fish oil triglyceride liquid on a milligram for milligram basis--is the ethyl ester form. That's not even factoring in reduced absorption of ethyl esters compared to triglyceride forms. Remember: FDA approval is not necessarily a stamp of superiority. It just means somebody had the money and ambition to pursue FDA approval. Period.
Taking any kind of fish oil, provided it is not overly oxidized (and thereby yields a smelly fish odor), is better than taking none at all. All fish oil will reduce triglycerides, accelerate clearance of postprandial (after-eating) lipoprotein byproducts of a meal (via activation of lipoprotein lipase), enhance endothelial responsiveness, reduce small LDL particles, and provide a physical stabilizing effect on atherosclerotic plaque.
But if you desire enhanced absorption and potentially lower dose to achieve equivalent RBC omega-3 levels, then triglyceride forms are better.
Here are cut-and-pasted abstracts of two of the studies comparing forms of fish oil.
Dyerberg J, Madsen P, Moller JM et al.
Department of Human Nutrition, Faculty of Life Sciences, University of Copenhagen, Copenhagen, Denmark.
Abstract
The use of marine n-3 polyunsaturated fatty acids (n-3 PUFA) as supplements has prompted the development of concentrated formulations to overcome compliance problems. The present study compares three concentrated preparations - ethyl esters, free fatty acids and re-esterified triglycerides - with placebo oil in a double-blinded design, and with fish body oil and cod liver oil in single-blinded arms. Seventy-two volunteers were given approximately 3.3g of eicosapentaenoic acid (EPA) plus docosahexaenoic acid (DHA) daily for 2 weeks. Increases in absolute amounts of EPA and DHA in fasting serum triglycerides, cholesterol esters and phospholipids were examined. Bioavailability of EPA+DHA from re-esterified triglycerides was superior (124%) compared with natural fish oil, whereas the bioavailability from ethyl esters was inferior (73%). Free fatty acid bioavailability (91%) did not differ significantly from natural triglycerides. The stereochemistry of fatty acid in acylglycerols did not influence the bioavailability of EPA and DHA.
Eur J Clin Nutr 2010 Nov 10.
Neubronner J, Schuchardt JP, Kressel G et al.
Institute of Food Science and Human Nutrition, Leibniz Universität Hannover, Am Kleinen Felde 30, Hannover, Germany.
Abstract
There is a debate currently about whether different chemical forms of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are absorbed in an identical way. The objective of this study was to investigate the response of the omega-3 index, the percentage of EPA+DHA in red blood cell membranes, to supplementation with two different omega-3 fatty acid (n-3 FA) formulations in humans. The study was conducted as a double-blinded placebo-controlled trial. A total of 150 volunteers was randomly assigned to one of the three groups: (1) fish oil concentrate with EPA+DHA (1.01?g+0.67?g) given as reesterified triacylglycerides (rTAG group); (2) corn oil (placebo group) or (3) fish oil concentrate with EPA+DHA (1.01?g+0.67?g) given as ethyl ester (EE group). Volunteers consumed four gelatine-coated soft capsules daily over a period of six months. The omega-3 index was determined at baseline (t(0)) after three months (t(3)) and at the end of the intervention period (t(6)). The omega-3 index increased significantly in both groups treated with n-3 FAs from baseline to t(3) and t(6) (P < 0.001). The omega-3 index increased to a greater extent in the rTAG group than in the EE group (t(3): 186 versus 161% (P < 0.001); t(6): 197 versus 171% (P < 0.01)). Conclusion: A six-month supplementation of identical doses of EPA+DHA led to a faster and higher increase in the omega-3 index when consumed as triacylglycerides than when consumed as ethyl esters.