Fish Oil Absorption – The Full Story
The main form of omega-3’s that relate to fish oil are ethyl ester and triglycerides and as science builds the case around them, we are becoming more aware of the different nuances to how they are absorbed and used in the body.
A study published in 2010 (Dyerberg J., 2010) continues to prompt many questions about the absorption superiority of different forms of omega-3’s. The study assessed the absorption of five different forms of fish oil supplements (re-synthesized triglycerides, ethyl esters, free fatty acid, cod liver oil, and fish body oil). Although the bioavailability was higher in fish oil given as triglyceride vs. ethylester, it does not make scientific sense to assume this is definitive proof around triglyceride superiority. Even the authors suggest this by concluding; “It should, however, be stressed that these conclusions are based on a relatively short-term (2 week) study at a fixed daily n-3 FA dose of approximately 3.5 g; 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” (Dyerberg J., 2010).
The scientific literature shows ample evidence that there is as much physiologically meaningful absorption, metabolism, and bioavailability of the ethyl ester form of omega-3 (Lawson LD, 1988) (Beckermann B, 1990) (Bryhn M, 2006) (Arterburn LM, 2006) (Rusca A, 2009). Furthermore, there have been a number of studies that have shown no difference between the ethyl ester and triglyceride forms, such as:
- Nordoy 1990 concluded that n-3 fatty acids in fish oil given as ethyl esters or triglyceride (esters) were equally well absorbed. Furthermore, EPA and DHA were also equally absorbed. Figure 1 shows the percentage of n-3 fatty acids of chylomicrons after the ingestion of 27 grams n-3 fatty acids from fish oil given as ethyl esters plus olive oil, as an ethyl ester and as a triglyceride. Olive oil was given as a control meal. (Nordoy, 1991)
Figure 1: Comparative effect of ethyl ester and triglyceride omega-3 absorption. (Nordoy, 1991).
- Krokan found that enteral absorption of EPA and DHA is as least as good from an ethyl ester highly enriched in EPA and DHA as it is from a triglyceride form containing equivalent amounts of these fatty acids. (Krokan H.E., 1993)
- Luley’s 1990 paper entitled “Bioavailability of omega-3 fatty acids: ethyl ester preparations are as suitable as triglyceride preparations” makes it clear that they also found similar absorption rates between the two forms. (Luley C., 1990)
- Reis found that fish oil supplementation with either a triglyceride or ethyl ester formulation produced significant and similar decreases in serum triglyceride levels and increases in LDL cholesterol levels. (Reis GJ, 1990)
- Simons concluded that fish oils in the form of ethyl esters or triglyceride are assimilated to a similar degree and lead to equivalent triglyceride-lowering in hypertriglyceridaemia, while simultaneously increasing LDL particle numbers (Simons, 1990).
- Hansen et al (1993) concluded that both formulas had equal inhibitory effects on collagen-induced platelet aggregation and thromboxane B2 (TxB2) production in whole blood. They concluded that TG and EE fish oils are well incorporated into plasma lipids and have similarly beneficial influence one platelet function in men. TG and EE fish oils are well incorporated into plasma lipids and have similarly beneficial influence on platelet function in men (Hansen JB, 1993).
Although many of these papers have similar weaknesses to the Dyerberg work (Dyerberg J., 2010) and they show the need for ongoing trials of suitable duration and methodology, they add enough scientific weight to conclude that the differences in ethyl ester and triglyceride omega-3s are minor, inconsequential, and cannot be judged to be physiologically or clinically significant.