Does krill oil contain more effective Omega-3 EPA and DHA than fish oil?

Omega-3s contained in krill oil are better absorbed compared to those found in fish oil; this is indicated by studies that have measured their blood levels and incorporation into red blood cell membranes following supplement intake. But are they also more effective? Let’s find out!

EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) are the two bioactive Omega-3s—the ones we need to harness the benefits of these health-supporting fats.

We can consume them preformed from marine sources. The most well-known are undoubtedly fish and oils derived from it (fish oil and cod liver oil); however, in recent years, krill oil, obtained from a tiny crustacean living in the cold waters of the southern seas—the Antarctic krill (Euphausia superba)—has become increasingly popular.

Krill is the main component of the zooplankton biomass found in Antarctic waters. Given the intense exploitation of marine fish populations, the possibility of using it as an alternative raw material for the production of Omega-3 supplements is very interesting.

Moreover, in krill oil, Omega-3s are present in the form of phospholipids—the main components of cell membranes into which Omega-3s incorporate to exert their benefits.

In natural fish oil, EPA and DHA are present in the form of triglycerides. During the production of Omega-3 supplements, this natural fish oil undergoes purification and concentration processes, resulting in products that may contain EPA and DHA in the form of ethyl esters (molecules different from those originally present in fish oil) or re-esterified triglycerides (more concentrated in Omega-3 than natural triglycerides but chemically similar).

Krill and fish Omega-3s: do differences in chemical form affect bioavailability?

Research over the years has suggested that these chemical differences between krill and fish Omega-3s correspond to greater bioavailability of EPA and DHA from krill oil—that is, better absorption.

Already in 2009, a research group led by Kevin Maki from the US Provident Clinical Research focused on this aspect, comparing EPA and DHA blood levels in 76 individuals (overweight men and women) who took 2 grams per day of krill oil, fish oil, or olive oil for 4 weeks.

"Significant increases compared to baseline EPA and DHA blood levels were observed with krill oil supplementation," explained Maki and colleagues. For krill oil, the average increase was 178.4 +/- 38.7 µmol/L for EPA and 90.2 +/- 40.3 µmol/L for DHA; for fish oil, the average increase was 131.8 +/- 28.0 µmol/L for EPA and 149.9 +/- 30.4 µmol/L for DHA.

Returning to the topic in 2010, a research group led by Stine Ulven at Akershus University College in Lillestrøm (Norway) observed similar increases in plasma EPA and DHA levels following krill and fish oil intake "even though," the researchers specified, "the EPA+DHA dose in krill oil was 62.8% of that in fish oil."

As Ulven and colleagues highlighted, "these results indicate that Omega-3 polyunsaturated fatty acids from krill oil (mainly phospholipids) are equally or even more bioavailable than those from fish oil (triglycerides)."

By standardizing the Omega-3 dose from fish oil and krill oil, Jan Philipp Schuchardt and colleagues at the University of Hannover (Germany) eliminated possible doubts, confirming that krill oil intake can achieve a greater increase in EPA+DHA levels in plasma phospholipids.

Finally, a study conducted in Canada by researchers from the Centre for Functional Foods and Nutraceuticals in Winnipeg revealed that krill oil increases the Omega-3 Index (Omega-3 Index)—the percentage of EPA and DHA among total fatty acids in red blood cell membranes—more effectively than fish oil.

As mentioned, one biological function of EPA and DHA is to integrate into cell membranes, providing the fluidity necessary for various cellular activities. The Omega-3 Index value (i.e., Omega-3 level in red blood cell membranes) is inversely proportional to the risk of cardiovascular problems, and the Canadian research, published in the journal Lipids in Health and Disease, contributed further to the discussion on the positive effects of krill oil.

This last study enrolled 24 healthy volunteers who participated in a trial organized into 3 different phases, each lasting 4 weeks, separated by an 8-week washout period. Volunteers, randomly divided into 3 groups, took 6 capsules per day containing krill oil, fish oil, or corn oil (placebo) during the treatments.

In the first phase, one group took krill oil, another fish oil, and another placebo; after 4 weeks of treatment and 8 weeks of washout, each group received another type of capsule for 28 days, and so on, allowing everyone to receive supplementation with both types of oil and placebo.

Omega-3 content in plasma and red blood cells of each volunteer was analyzed before and after each phase. After each phase, a greater increase in Omega-3 levels in plasma and red blood cells was observed in subjects who had received krill oil supplements or fish oil. However, a difference emerged between the two: the Omega-3 Index change after krill oil and fish oil consumption was 1.04% and 0.47%, respectively.

Furthermore, a reduction in Omega-6 concentration (polyunsaturated fats generally more pro-inflammatory than Omega-3s) was observed in volunteers receiving these supplements. In particular, those who took krill oil showed a greater increase in Omega-3 and reduction in Omega-6 compared to those who took fish oil.

The probable role of phospholipid structure and free fatty acids

Scientists hypothesize that, thanks to the phospholipid structure, krill Omega-3s may be more easily absorbed and incorporated into cell membranes than those in fish oil triglycerides.

Moreover, analyzing the fat structure in the supplements used in their study, Schuchardt and colleagues found a significant portion of EPA and DHA (22% and 21%, respectively) in the form of free fatty acids, which were absent in fish oil. This, the researchers explain, "could significantly influence the bioavailability of EPA and DHA from krill oil."

Only further studies will help prove this hypothesis and clarify the mechanism behind the better absorption of fats present in this Omega-3 source.

Is krill oil more effective than fish oil?

Data collected from these trials suggest that krill oil supplements may exert a better protective effect against cardiovascular diseases compared to fish oil supplements.

This aspect has been explored in some of these and other studies. In 2015, Ulven, together with Kirsten Holven from the University of Oslo (Norway), reviewed the situation. Writing in Vascular Health and Risk Management, the two experts concluded that "krill oil regulates more metabolic pathways than fish oil" and that this "might indicate different biological effects of krill oil compared to fish oil."

A few years later, a Korean research group analyzed the available evidence on the effects of these two marine oils on blood lipid levels. "The differences in triglycerides, LDL cholesterol, HDL cholesterol, and total cholesterol were not significant," the experts explained in Nutrition Reviews, concluding that "the effects of krill oil and fish oil on lipids (i.e., cholesterol and blood triglycerides) are not different" and that "the reduction in triglycerides," which is one of the main reasons EPA and DHA supplements are prescribed, "depends on the dose of Omega-3 fatty acids taken."

Krill oil: a valid and safe alternative to fish oil

Based on the available data, it is reasonable to conclude that krill oil represents a valid alternative to fish oil. Its intake has not been associated with concerning side effects; the only absolute contraindication remains, at least for now, allergy to crustaceans.

It is worth remembering that besides EPA and DHA, krill oil also contains a powerful natural antioxidant (astaxanthin) and choline, a molecule beneficial for heart and liver health. Discover all its features by reading this in-depth article: Krill oil, all the benefits and properties.

References:

European Commission. Food and Feed Information Portal Database. Last accessed: 04/24/25

Kim MG, Yang I, Lee HS, Lee JY, Kim K. Lipid-modifying effects of krill oil vs fish oil: a network meta-analysis. Nutr Rev. 2020 Sep 1;78(9):699-708. doi: 10.1093/nutrit/nuz102

Maki KC, Reeves MS, Farmer M, Griinari M, Berge K, Vik H, Hubacher R, Rains TM. Krill oil supplementation increases plasma concentrations of eicosapentaenoic and docosahexaenoic acids in overweight and obese men and women. Nutr Res. 2009 Sep;29(9):609-15. doi: 10.1016/j.nutres.2009.09.004

Ramprasath VR, Eyal I, Zchut S, Jones PJ. Enhanced increase of omega-3 index in healthy individuals with response to 4-week n-3 fatty acid supplementation from krill oil versus fish oil. Lipids Health Dis. 2013 Dec 5;12:178. doi: 10.1186/1476-511X-12-178

Schuchardt JP, Schneider I, Meyer H, Neubronner J, von Schacky C, Hahn A. Incorporation of EPA and DHA into plasma phospholipids in response to different omega-3 fatty acid formulations--a comparative bioavailability study of fish oil vs. krill oil. Lipids Health Dis. 2011 Aug 22;10:145. doi: 10.1186/1476-511X-10-145

Ulven SM, Holven KB. Comparison of bioavailability of krill oil versus fish oil and health effect. Vasc Health Risk Manag. 2015 Aug 28;11:511-24. doi: 10.2147/VHRM.S85165

Ulven SM, Kirkhus B, Lamglait A, Basu S, Elind E, Haider T, Berge K, Vik H, Pedersen JI. Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA, in healthy volunteers. Lipids. 2011 Jan;46(1):37-46. doi: 10.1007/s11745-010-3490-4