What Is Krill Oil? How It Differs from Fish Oil, DHA and the Evidence

Krill oil is an oil taken from a small marine crustacean called Antarctic krill, and it carries omega-3 fatty acids such as EPA and DHA largely bound to phospholipids. In some small studies it raised blood omega-3 levels more than fish oil did, but whether that difference leads to outcomes for the brain or vision is unclear, and researchers say more studies are needed. This article explains what krill oil is, how it differs from fish oil, and what is and is not established about the brain and the eyes.

What is krill oil?

Krill are tiny shrimp-like crustaceans that live in the oceans. Supplements mostly use oil from Antarctic krill. Like fish oil it supplies EPA and DHA, and it naturally contains a small amount of astaxanthin, a red-orange carotenoid. In many krill products EPA is higher than DHA, so a "DHA-rich" description varies by product and should be checked against the amounts on the label.

Why DHA comes up for the brain and the eyes

The US National Institutes of Health Office of Dietary Supplements (NIH ODS) notes that DHA levels are especially high in the retina, the brain and sperm cells, which shows that DHA is part of the structure of these tissues. But a nutrient being present in a tissue does not mean taking it as a supplement will improve vision or memory; that is a separate question that studies have to answer.

Vision: what does the evidence say?

In AREDS2, a large trial of 4,203 participants published in JAMA in 2013, adding DHA and EPA to the existing formula did not further reduce the risk of progression to advanced age-related macular degeneration. That result does not support the idea that omega-3 supplements are clearly beneficial for the eyes. Decisions about eye health belong with an eye doctor, and krill oil should not be thought of as a treatment or a fix.

How krill oil differs from fish oil

• Chemical form: In fish oil the omega-3s are mostly triglycerides or ethyl esters; in krill oil a substantial share is bound to phospholipids.
• Blood levels: In a 2011 comparative bioavailability study by Schuchardt and colleagues, krill oil gave the highest incorporation of EPA+DHA into plasma phospholipids, and the authors said larger studies were needed to support the findings. In a 2013 double-blind crossover study of 24 healthy volunteers by Ramprasath and colleagues, both oils supplied 600 mg of omega-3s, and krill oil raised the omega-3 index more clearly than fish oil.
• Overall view: A 2015 review by Ulven and Holven says there may be a difference in EPA and DHA bioavailability between the two, but that more studies are needed before a firm conclusion.

So rather than saying "krill oil is better than fish oil", it is more accurate to say it appeared to raise blood omega-3 levels more effectively in some studies, while it is unknown whether the difference translates into clinical outcomes.

About astaxanthin

Astaxanthin is a carotenoid pigment found naturally in krill and is studied for its antioxidant properties. The amount in krill oil is small and varies by product. We make no claims here about its effect on the stability of omega-3s or on the eyes.

What to check when choosing krill oil

1. EPA and DHA amounts: What matters is the EPA and DHA per serving, not the total oil.
2. Source and processing: Is it Antarctic krill, where is it made, is there certification or third-party testing? Our guide to supplement ingredient quality covers these checks.
3. Allergens: Krill is a crustacean, so people with shellfish allergy should be especially careful.
4. Medicine interactions: If you take blood-thinning medication, ask your doctor before using omega-3s.
5. Price and serving: Compare the cost per EPA+DHA; a high price is not proof of quality.

For the idea that more ingredients do not mean a better product, see more ingredients, better supplement? For a general framework on brain-related supplements, read how to choose a high-quality nootropic supplement.

About Root's KO3

Root describes a product called KO3, an Antarctic krill oil with phospholipid-bound omega-3s and astaxanthin. It is not sold on our site, so there is no purchase link here. We have not verified Root's statements that it is "better for brain and vision" against independent evidence, and we do not repeat them.

References

1. Schuchardt JP, Schneider I, Meyer H, et al. 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 in Health and Disease. 2011;10:145. doi.org/10.1186/1476-511X-10-145.
2. 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 in Health and Disease. 2013;12:178. doi.org/10.1186/1476-511X-12-178.
3. Ulven SM, Holven KB. Comparison of bioavailability of krill oil versus fish oil and health effect. Vascular Health and Risk Management. 2015;11:511-524. doi.org/10.2147/VHRM.S85165.
4. Age-Related Eye Disease Study 2 (AREDS2) Research Group. Lutein + zeaxanthin and omega-3 fatty acids for age-related macular degeneration: the AREDS2 randomized clinical trial. JAMA. 2013;309(19):2005-2015. doi.org/10.1001/jama.2013.4997.
5. US National Institutes of Health, Office of Dietary Supplements: Omega-3 Fatty Acids, consumer fact sheet.

Conclusion

Krill oil is one way to get omega-3s, and in some studies it raised blood levels more effectively than fish oil, but its superiority for the brain or vision has not been shown. When choosing a supplement, look at EPA and DHA amounts, source, allergens and quality, and keep a balanced diet that includes fish, seafood and plant sources as your foundation.