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Krill Oil vs. Fish Oil: What's the Difference?
When the topic of omega-3 comes up, many people immediately think of fish oil supplements. However, in recent years, an alternative omega-3 supplement has been gaining significant interest: krill oil, which is derived from krill, tiny, shrimp-like marine crustaceans.
Both supplements provide omega-3s; however, the major differences between these two marine oils are often unknown. These differences are evident in their composition, rate of absorption, and the consumer's experience with the product. This article will examine how krill oil differs from the familiar fish oil—and why it might be a better choice.
The Source: Fish vs. Krill
Although both supplements originate from marine sources, their origins are quite different. Fish oil is typically extracted from fatty fish such as salmon, anchovies, sardines, and mackerel. Krill oil, on the other hand, is derived from Antarctic krill—small crustaceans that live in large swarms in the Southern Ocean.
Because krill are small organisms positioned low on the food chain, they inherently face a significantly lower risk of heavy metal buildup compared to larger fish. Consequently, krill oil is naturally less susceptible to environmental contaminants.
Form of Omega-3
While both fish oil and krill oil provide the key omega-3 fatty acids EPA and DHA, they differ in the form these fatty acids take.
- Fish oil: Omega-3 is mainly in triglyceride or ethyl ester form. These must be digested and absorbed similarly to fats in a typical meal.
- Krill oil: Omega-3 is in the phospholipid form, the same structural components found in human cell membranes. This makes them much easier for the body to absorb and use effectively.
This structural difference affects how they should be taken: Fish oil works best when consumed with food so the body can properly digest and absorb it. Krill oil, however, can usually be taken at any time, even without a meal, because its phospholipid form is easily absorbed.
Other Key Nutrients in Krill Oil
Beyond omega-3, krill oil naturally contains other health-supportive compounds not found in fish oil:
- Choline: An essential nutrient involved in brain function, liver health, muscle performance, and nerve signaling. The body produces only small amounts, so dietary intake is important.
- Astaxanthin: A powerful red antioxidant that gives krill oil its characteristic color. Astaxanthin helps protect cells from oxidative damage and supports skin and eye health. It also helps keep krill oil stable, reducing the risk of oxidation and rancidity.
Possible Side Effects
Both fish oil and krill oil are generally safe, but some individuals may experience mild digestive symptoms such as nausea, bloating, or stomach discomfort.
One notable difference is that fish-oil users often report fishy burps, due to its stronger odor and higher tendency to oxidize. Krill oil tends to cause this far less frequently, as it is absorbed more efficiently and does not linger in the stomach as long. For people sensitive to the taste or smell of fish oil, krill oil may be a more tolerable choice.
Raising Omega-3 Levels: How Effective?
Both fish oil and krill oil are beneficial to brain, heart, eye, and joint health. However, due to the phospholipid form of omega-3s, krill oil may raise Omega-3 levels in the body more effectively.
For example, a study by Vanu R. Ramprasath et al. compared krill oil and fish oil supplementation over four weeks in healthy adults. Despite providing equal amounts of EPA and DHA, krill oil led to a significantly greater increase in the omega-3 Index. This suggests that krill oil may be more efficiently absorbed and utilized by the body.
Increasing the omega-3 Index is important, as higher levels are associated with reduced inflammation, better cardiovascular function, improved cognitive protection, and healthier eyes and joints.
In summary, while both krill oil and fish oil provide essential omega-3 fatty acids, their distinct molecular structures, components, and absorption rates mean they offer different results and consumer experiences. Consumers are advised to evaluate these differential benefits and select an omega-3 supplement that aligns optimally with their specific health objectives and practical consumption preferences to achieve maximal efficacy.
Reference
1. Austwick, M. (2025, August 13). Astaxanthin: Benefits, natural sources, and more. Medical News Today. https://www.medicalnewstoday.com/articles/astaxanthin
2. Harvard T.H. Chan School of Public Health. Choline. The Nutrition Source. https://nutritionsource.hsph.harvard.edu/choline/
3. IFFO - The Marine Ingredients Organisation. The sources of marine ingredients: Whole fish & by-products. https://www.iffo.com/sources-marine-ingredients-whole-fish-products
4. Mayo Clinic Staff. (2023, August 10). Fish oil. Mayo Clinic. https://www.mayoclinic.org/drugs-supplements-fish-oil/art-20364810
5. Ramprasath, V. R., Eyal, I., Zchut, S., & Jones, P. J. H. (2013). 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, 12(1), Article 178. https://doi.org/10.1186/1476-511X-12-178
6. Superba Krill. What is krill oil? https://www.superbakrill.com/krill-oil/what-is-krill-oil
7. Superba Krill. (2023, January 12). Krill oil phospholipids work at a cellular level to promote healthy aging. https://www.superbakrill.com/blog/krill-oil-phospholipids-work-at-a-cellular-level-to-promote-healthy-aging