Abstract
BackgroundBioavailability of omega-3 fatty acids (FA) depends on their chemical form. Superior bioavailability has been suggested for phospholipid (PL) bound omega-3 FA in krill oil, but identical doses of different chemical forms have not been compared.MethodsIn a double-blinded crossover trial, we compared the uptake of three EPA+DHA formulations derived from fish oil (re-esterified triacylglycerides [rTAG], ethyl-esters [EE]) and krill oil (mainly PL). Changes of the FA compositions in plasma PL were used as a proxy for bioavailability. Twelve healthy young men (mean age 31 y) were randomized to 1680 mg EPA+DHA given either as rTAG, EE or krill oil. FA levels in plasma PL were analyzed pre-dose and 2, 4, 6, 8, 24, 48, and 72 h after capsule ingestion. Additionally, the proportion of free EPA and DHA in the applied supplements was analyzed.ResultsThe highest incorporation of EPA+DHA into plasma PL was provoked by krill oil (mean AUC0-72 h: 80.03 ± 34.71%*h), followed by fish oil rTAG (mean AUC0-72 h: 59.78 ± 36.75%*h) and EE (mean AUC0-72 h: 47.53 ± 38.42%*h). Due to high standard deviation values, there were no significant differences for DHA and the sum of EPA+DHA levels between the three treatments. However, a trend (p = 0.057) was observed for the differences in EPA bioavailability. Statistical pair-wise group comparison's revealed a trend (p = 0.086) between rTAG and krill oil. FA analysis of the supplements showed that the krill oil sample contained 22% of the total EPA amount as free EPA and 21% of the total DHA amount as free DHA, while the two fish oil samples did not contain any free FA.ConclusionFurther studies with a larger sample size carried out over a longer period are needed to substantiate our findings and to determine differences in EPA+DHA bioavailability between three common chemical forms of LC n-3 FA (rTAG, EE and krill oil). The unexpected high content of free EPA and DHA in krill oil, which might have a significant influence on the availability of EPA+DHA from krill oil, should be investigated in more depth and taken into consideration in future trials.
Highlights
Bioavailability of omega-3 fatty acids (FA) depends on their chemical form
Differences in plasma PL levels between re-esterified TAG (rTAG), EE and krill oil are demonstrated in Table 3, which shows the EPA, DHA and total n-3 FA gradients as AUC0-72, cmax and tmax values
In a randomized crossover study in healthy volunteers, we observed the highest incorporation of EPA, DHA and total n-3 FA into plasma PL after the ingestion of krill oil (PL and free FA (FFA)), followed by rTAG derived from fish oil, again followed by EE
Summary
Superior bioavailability has been suggested for phospholipid (PL) bound omega-3 FA in krill oil, but identical doses of different chemical forms have not been compared. We demonstrated that a six-month supplementation of identical doses of EPA+DHA (1.67 g/d) leads to a faster and higher increase of the omega-3 index - the percentage of EPA and DHA in red cell membranes reflecting the long-term intake and n-3 FA status of an individual [5] - when consumed as rTAG than when consumed as EE [6]. Our results were in line with data from a short-term study of two weeks duration measuring the FA compositions of serum cholesterol-esters, TAG and phospholipids (PL): relative bioavailability of EPA+DHA from rTAG was superior (124%) compared with cod liver oil (100%), whereas the bioavailability from EE was inferior (73%) [7]. The dose of EPA+DHA in krill oil was 62.8% of that in fish oil, but similar changes in plasma EPA+DHA and of a lipid panel were observed [15]
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