Is it better to take krill or fish oil? A comprehensive guide for your nutritional diet

October 6, 2025 •

5 min read

Over two-thirds of U.S. adults may not consume enough omega-3 fatty acids, vital nutrients for maintaining health. When seeking to supplement, a common question is: is it better to take krill or fish oil? The answer depends on individual priorities, including bioavailability, cost, and additional compounds.

Quick Summary

This guide compares krill oil and fish oil, highlighting differences in molecular structure, absorption rates, antioxidant content, and cost. It details their shared and distinct health benefits and risks to inform your decision on the ideal omega-3 supplement.

Key Points

Superior Absorption: Krill oil's omega-3s are bound to phospholipids, enhancing absorption and delivery to cells compared to fish oil's triglyceride form.
Added Antioxidant: Krill oil naturally contains the powerful antioxidant astaxanthin, which protects the oil from oxidation and provides additional health benefits.
Higher Concentration & Cost: Fish oil generally offers a higher omega-3 concentration per serving and is more budget-friendly than krill oil.
Reduced Aftertaste: Many users find krill oil causes fewer "fishy burps" and digestive issues compared to fish oil.
Purity and Research: Krill oil is lower in contaminants like mercury, while fish oil has decades of more extensive human research backing its benefits.
Shellfish Allergy Alert: Individuals with a shellfish allergy should avoid krill oil due to its crustacean source.
Individual Needs Matter: The best choice ultimately depends on personal factors like budget, digestive tolerance, and specific health goals.

Both krill oil and fish oil are popular sources of omega-3 polyunsaturated fatty acids (PUFAs), specifically eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). These fatty acids are essential because the human body cannot produce them efficiently and must obtain them through diet or supplementation. Omega-3s play a critical role in brain development, cardiovascular health, and reducing inflammation. While their benefits overlap, fundamental differences in their composition, bioavailability, and cost may influence which one is the better choice for you.

The Fundamental Differences: Krill vs. Fish Oil

Molecular Structure and Absorption

One of the most significant distinctions between the two oils lies in the form of their omega-3s.

Krill Oil: The omega-3s in krill oil are primarily bound to phospholipids, which form the building blocks of human cell membranes. This structure is believed to enhance omega-3 absorption and its delivery to cells, including those in the brain. The phospholipid form also aids emulsification in the stomach, potentially reducing the unpleasant "fishy burps" often associated with marine oil supplements.
Fish Oil: The omega-3s in standard fish oil are typically bound to triglycerides, a form of fat commonly found in the body. For absorption, these triglycerides must be broken down by digestive enzymes. While still effective, some studies suggest this process is less efficient than the phospholipid absorption of krill oil.

Antioxidant Content

Krill oil contains an additional compound that fish oil lacks: astaxanthin.

Krill Oil: The reddish color of krill oil comes from astaxanthin, a powerful antioxidant. Astaxanthin helps protect the oil from oxidation, maintaining its freshness and potency. It also offers additional health benefits, including potent anti-inflammatory effects and protection against oxidative stress.
Fish Oil: Fish oil does not naturally contain astaxanthin and is therefore more susceptible to oxidation, which can cause the oil to go rancid over time. High-quality fish oil supplements are often processed to prevent this and may contain added antioxidants, like vitamin E.

Omega-3 Concentration and Cost

When considering the potency and price, there is a trade-off between the two supplements.

Fish Oil: Typically offers a higher overall concentration of EPA and DHA per serving. It is generally more affordable and widely accessible, making it a cost-effective choice for those needing higher omega-3 doses.
Krill Oil: Contains a lower concentration of total omega-3s per capsule than fish oil. Due to more complex harvesting and processing methods, it is significantly more expensive.

Purity and Sustainability

Concerns over contaminants and environmental impact can also be a deciding factor.

Krill Oil: Krill are at the bottom of the marine food chain, so they accumulate fewer toxins like mercury than larger fish. However, the harvesting of krill has raised some environmental concerns regarding its role as a key food source for Antarctic ecosystems. Responsible brands carry Marine Stewardship Council (MSC) certification to address this.
Fish Oil: The risk of contamination, particularly with mercury, is higher with fish oil, especially from larger fish species. Reputable manufacturers use purification and distillation processes to remove these contaminants. Sustainable sourcing is also a factor, varying depending on the fish species used.

Health Benefits: How Do They Compare?

Both krill oil and fish oil offer similar science-backed health benefits, mainly attributed to their EPA and DHA content. However, some studies suggest potential differences in efficacy.

Heart Health: Both are known to reduce triglyceride levels, lower blood pressure, and support overall cardiovascular health. Some research indicates krill oil may be particularly effective at lowering triglycerides and improving cholesterol ratios, possibly at a lower dose.
Brain Function: EPA and DHA are vital for brain health. Krill oil's phospholipid-bound omega-3s may enhance delivery to the brain, potentially offering benefits for cognitive function.
Inflammation and Joint Health: The anti-inflammatory properties of omega-3s can benefit conditions like rheumatoid and osteoarthritis. The added astaxanthin in krill oil may provide extra antioxidant support and help reduce inflammation.

Comparison at a Glance: Krill Oil vs. Fish Oil


Feature	Krill Oil	Fish Oil
Omega-3 Structure	Phospholipid-bound	Triglyceride-bound
Absorption	Potentially superior, may reach cells more directly	Effective, but requires more digestive processing
Antioxidant	Contains astaxanthin, a potent antioxidant	Contains no natural astaxanthin, more prone to oxidation
Cost	Generally more expensive due to complex sourcing	Typically more affordable and accessible
Omega-3 Concentration	Lower total EPA/DHA concentration per gram	Higher total EPA/DHA concentration per gram
Purity Concerns	Lower risk of mercury, but can contain fluoride if not processed properly	Higher risk of mercury from larger fish, but purified effectively by reputable brands
Side Effects	Fewer reports of "fishy burps"	More common incidence of "fishy burps" and indigestion
Research	Less extensive long-term human research	Decades of extensive research support its benefits

How to Choose the Right Supplement

Your choice between krill oil and fish oil depends on what you prioritize in an omega-3 supplement. Here are some key considerations:

Budget: If cost is your primary concern, and you need a high dose of omega-3s, fish oil is the more economical option. You can find high-quality, purified fish oil supplements for a fraction of the price of krill oil.
Digestion and Absorption: For those who experience a fishy aftertaste or belching with fish oil, krill oil's phospholipid structure may provide a more pleasant digestive experience. If you believe you have poor fat absorption, krill oil's superior bioavailability could be advantageous.
Additional Antioxidants: If you are looking for the combined benefits of omega-3s and a potent antioxidant like astaxanthin, krill oil is the natural choice. While you can supplement with astaxanthin separately, krill oil offers both in one capsule.
Shellfish Allergies: Individuals with shellfish allergies should strictly avoid krill oil, which is derived from crustaceans. Fish oil is a safe alternative, assuming there are no fish allergies.
Sustainability and Purity: For those concerned about environmental impact, check for third-party certifications like the MSC label on krill oil products. For fish oil, choose brands that clearly state their purification processes to ensure safety from contaminants like mercury.

Conclusion

There is no single "better" answer to whether to take krill or fish oil, as both are excellent sources of the essential omega-3s, EPA, and DHA. Krill oil offers potential advantages in absorption due to its phospholipid form and contains the added antioxidant astaxanthin, but it comes at a higher price. Fish oil is a more cost-effective and widely researched option, providing higher concentrations of EPA and DHA per serving. Ultimately, the best choice depends on your individual health needs, budget, and tolerance. It is always wise to consult with a healthcare professional before starting any new dietary supplement, especially if you have underlying health conditions or are taking other medications.

Visit the NIH Office of Dietary Supplements for more information on Omega-3 Fatty Acids.

Frequently Asked Questions

Both krill and fish oil support heart health by lowering triglycerides and blood pressure. Some studies suggest krill oil may be more effective for improving cholesterol ratios, even at lower doses, while fish oil has a longer history of research.

Both oils have anti-inflammatory effects that can help reduce joint pain and swelling. Krill oil's unique phospholipid structure may offer quicker relief, and its astaxanthin content provides extra antioxidant benefits that may combat inflammation.

Fish oil typically contains a higher overall concentration of EPA and DHA per serving than krill oil. This is an important consideration if you need to consume a high dose of these fatty acids.

Yes, many users report fewer instances of "fishy burps" and a better digestive experience with krill oil. This is because the omega-3s in krill oil are phospholipid-bound, which helps them emulsify and absorb more easily in the stomach.

Krill oil generally has a lower risk of contaminants like mercury because krill are lower on the food chain. Reputable fish oil brands, however, use extensive purification processes to remove toxins from their products.

People with a shellfish allergy should not take krill oil, as it is derived from tiny crustaceans. Additionally, if you are on blood-thinning medication, you should consult a doctor before taking either krill or fish oil.

For most people, eating two to three servings of oily fish per week, such as salmon or sardines, is enough to get the recommended intake of omega-3s. Supplements are a reliable alternative for those who don't consume enough fish or have specific health needs, like very high triglycerides.