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Importantly, the researchers say, their study took care to ensure that the concentrations of EPA and DHA in the supplements administered, whether from fish oil or krill oil, were equal.
Krill oil’s claim to fame in the omega-3 market has long been its phospholipid structure, which krill oil suppliers and marketers tout as more bioavailable compared to fish-oil omega-3s. DSM Nutritional Products (Parsippany, NJ), a supplier of both algae and fish-oil omega-3s, has funded a study that compared fish oil and krill oil and concluded that bioavailability is equal between the two.
The four-week, randomized, double-blind study1 published in the journal Lipids in Health and Disease was conducted in 66 healthy adults. Subjects were supplemented daily with a 1.3 g/day dose of EPA+DHA, either as fish oil ethyl ester (supplied by DSM), fish oil triglyceride (supplied by DSM), or krill oil (the NutriGold Double Strength Krill Gold supplement featuring krill oil from Neptune Technologies and Bioressources Inc.).
Importantly, the researchers say, their study took care to ensure that the concentrations of EPA and DHA in the supplements administered, whether from fish oil or krill oil, were equal. In all three interventions, subjects received roughly a total of 816 mg/day of EPA and 522 mg/day of DHA.
Plasma and red blood cell measurements were taken at baseline and at 4, 8, 12, 48, 72, 336, and 672 hours (the end of four weeks) into the study.
According to researchers, there were no significant differences in total plasma EPA+DHA concentrations at the end of the four-week study between either the fish oil ethyl ester, the fish oil triglyceride, or the krill oil group. “Additionally, DHA+EPA levels were not significantly different in [red blood cells] among the three formulations….providing comparable omega-3 indexes,” the stated.
“In conclusion, our results demonstrate similar plasma and [red blood cell] levels of EPA+DHA were achieved with fish oil and krill oil products when matched for dose and EPA+DHA content in this four-week study, indicating comparable oral bioavailability irrespective of formulation,” they wrote.
But the researchers did also allow for the fact that “it is possible that the phospholipid content in krill oil may affect its bioavailability,” pointing out that “krill oil composition in various commercial products varies widely in phospholipid content from approximately 19%–81% and this has not been systematically examined in longer-term dosing trials.” But they said, at least with the krill oil supplement tested in this study, bioavailability equaled that of fish oil.
The researchers said this study may shed more accurate light on the bioavailability debate because, unlike previous studies, this trial used similar DHA and EPA concentrations across the board. Previous studies comparing fish oil to krill oil supplementation did not match the doses or the concentrations of DHA and EPA per supplement, “making comparative bioavailability of these oils difficult.”
In a press release, DSM said that “several krill oil manufacturers and marketers have made, and continue to make, claims that krill oil is between 2.5 and 20 times more bioavailable than fish-oil forms of omega-3” and more bioavailable than algal oil, too.
The study’s lead researcher Karin Yurko-Mauro, PhD, director of clinical research, nutritional lipids, at DSM, said, “It has previously been suggested that krill oil has greater bioavailability than fish or algal oil, but the studies referenced to make such claims had critical design flaws. This new study was designed to objectively determine if there are significant differences in the bioavailability of different forms of omega-3 dose for dose, in order to provide more evidence and give a clear message to consumers.”
Read these other Nutritional Outlook articles on the omega-3 bioavailability debate:
Nutritional Outlook magazine
1. Yurko-Mauro K et al., “Similar eicosapentaenoic acid and docosahexaenoic acid plasma levels achieved with fish oil or krill oil in a randomized, double-blind, four-week bioavailability study,” Lipids in Health and Disease, vol. 14, no. 1. Published online September 2, 2015.