Key takeaways:
Both krill oil and fish oil may help limit risk factors linked to heart disease, including triglyceride (blood fat) and cholesterol levels.
Some evidence suggests krill oil may be better absorbed than fish oil. But more research is needed.
For some, krill oil supplements are smaller and easier to tolerate.
Omega-3 fatty acids are among the most commonly consumed supplements in the U.S. Within this category are two common types: krill oil and fish oil. But does one type have a slight edge over the other? Here’s what you need to know about their differences and effects on your health.
What is the difference between krill oil vs. fish oil?
The main differences between krill oil and fish oil come down to their sources. Krill oil is extracted from krill, small shrimp-like crustaceans (shellfish) that eat algae. Fish oil, on the other hand, comes from fatty fish like salmon, tuna, cod, and sardines.
Let’s take a look at three key differences between krill oil and fish oil.
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1. Fish oil supplements usually contain more omega-3 fatty acids
Research suggests that around 2,000 mg to 3,000 mg of omega-3s may be needed for heart-protective benefits. Fish oil supplements are typically higher in omega-3 fatty acids compared to krill oil supplements.
On average, one fish oil supplement contains 300 mg of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) omega-3 fatty acids. Typical amounts of omega-3s in krill oil supplements range from 45 mg to 200 mg of DHA and EPA per capsule.
That said, the amount of omega-3s can vary by brand, and prescription doses tend to be higher. You’ll need to check the label of your supplement to find out the amount of omega-3s present.
2. Krill oil supplements are more likely to contain other antioxidants
Not only does krill oil contain both DHA and EPA omega-3 fatty acids, but it also contains the antioxidant astaxanthin, which gives it a red color. This powerful antioxidant has anti-inflammatory properties that help promote heart health.
Krill oil also offers choline. This compound is important for nervous system development in infants and healthy brain function in adults.
Except for salmon oil, most fish oils don’t routinely contain these added antioxidants.
Eating fish vs. fish oil supplements: Find out why it’s best to try and get omega-3s from your diet if possible.
Non-fish omega-3 sources: Learn the best ways to get omega-3s if you don’t eat fish.
Different types of omega fatty acids: Explore the differences between omega-3, omega-6, and omega-9 fatty acids, and their benefits.
3. Krill oil may be more easily absorbed
Although more research is needed, some evidence suggests krill oil might be better absorbed than fish oil. In other words, krill oil seems to raise levels of EPA and DHA omega-3s more than fish oil supplements of equivalent doses. The evidence for better absorption is limited. And whether this leads to more health benefits is still up for debate. Researchers recommend more controlled studies to determine if krill oil’s better absorption means more health benefits compared to fish oil.
Benefits of krill oil vs. fish oil
It appears that both krill oil and fish oil supplements are similarly effective in lowering blood fat and inflammation. In general, omega-3s may be helpful with:
Lowering triglyceride and low-density lipoprotein (LDL), or “bad” cholesterol, levels
Lessening symptoms of dry eye disease
Growth and development in babies
Lowering the risk of vision problems like age-related macular degeneration
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Below is a closer look at possible benefits of each type of supplement.
Krill oil benefits
In addition to being readily absorbed by your body, krill oil has other possible health benefits, including:
Limiting knee pain in people with to mild-to-moderate osteoarthritis
Improving muscle function in healthy older adults
Fish oil benefits
Apart from it being used as a supplement for high triglyceride levels and rheumatoid arthritis, other possible health benefits of fish oil include:
Lowering your risk of heart attack
Improving cognitive function in older adults with well-controlled heart disease
Curbing symptoms of postpartum depression
Lowering blood pressure in people at higher risk of heart disease
Which omega-3 is better for heart health?
While both krill oil and fish oil are thought to have similar effects on heart health, only fish oil has been tied to a lower risk of heart-related events in high-risk people.
For example, a large study found that supplementing with fish oil greatly lowered the relative risk of a heart attack and death in people who had previously experienced a heart attack by 30% or more. The form of fish oil used in the study was icosapent ethyl, which only has EPA, not DHA.
Although krill oil shows promise, there isn’t enough evidence to confirm its benefits for heart health. Similarly, even though it has choline and astaxanthin, there isn’t research to determine whether these nutrients give krill an advantage over fish oil.
Side effects of krill oil vs. fish oil
While generally safe to take, there have been reports of mild side effects from both krill oil and fish oil supplements. The most common side effects are listed below.
Krill oil | Fish oil | |
Swallowing | Small, soft gel pills that tend to be easy to swallow | Large pills that some people have trouble swallowing A liquid format is also available |
Aftertaste | None reported | Fishy “burp” |
Abdominal issues | Flatulence (gas), diarrhea, and heartburn | Nausea and vomiting |
Atrial fibrillation | No research available | Some evidence suggests 4 g/day may raise your risk |
Medication interactions | Small risk of interacting with anticoagulants | Small risk of interacting with anticoagulants |
Allergic reaction | Possible for those with shellfish allergies | Possible for those with seafood allergies |
Mercury/PCB contamination | Trace amounts of mercury might be present One brand was found to contain fish oil, have low omega-3 content, and show signs of spoilage. | Trace amounts of mercury might be present Lower-quality fish oil supplements may carry a possible risk of PCB (polychlorinated biphenyl) contamination |
Who should not take krill oil or fish oil?
Anyone allergic to fish or shellfish should avoid taking fish oil or krill oil. Plus, anyone with the following medical conditions should check with a healthcare professional before taking either supplement:
Heart disease
Bleeding disorders
Pregnancy
How to take omega-3 oils
Some evidence suggests taking omega-3 oil supplements with meals containing fat can help with absorption. Dividing the dose — taking half with your morning meal and half with your evening meal — may make them easier to tolerate.
If you have trouble swallowing pills, liquid fish oil products are available. These can be mixed into food, such as smoothies and yogurt. Be sure to store the oil in your fridge to limit oxidation and spoilage.
How much omega-3 oil should I take?
While there’s no recommended daily amount for DHA and EPA omega-3 fatty acids, adequate intake for adults older than 19 ranges from 1.1 g to 1.6 g, depending on sex and pregnancy status. The FDA has said that supplements containing no more than 5 g of EPA and DHA per day are safe. But, it’s always best to talk with a healthcare professional to find out the right dose for you.
Cost of krill oil vs. fish oil supplements
Krill oil supplements tend to be smaller and more expensive than fish oil supplements. While krill oil may be better absorbed, it’s unclear whether taking a lower dose would offer any noticeable benefit.
Many supplements are a blend of krill oil and fish oil and may be less expensive than pure krill oil.
Natural food sources of krill oil and fish oil
Keep in mind that many people can get the recommended amount of fish oils through their diet. Eating at least 2 servings of fatty fish a week has been shown to limit the risk of cardiovascular disease.
The best food sources of DHA and EPA omega-3s include:
Salmon
Herring
Sardines
Mackerel
Trout
Sea bass
Oysters
Although plant oils, seeds, and nuts have another type of omega-3 called alpha-linolenic acid (ALA), your body doesn’t efficiently convert it into EPA and DHA, which are more helpful. Many foods fortified with omega 3s — like eggs, juice, and certain dairy products — also include ALA rather than EPA and DHA.
Should I consult a healthcare professional before taking omega-3s?
Yes, even if you’re healthy, it’s a good idea to talk with a healthcare professional before taking any supplement — including krill oil or fish oil.
Also, if you’re scheduled for surgery or planning a surgical procedure, talk with your surgeon to find out if and when you should stop taking omega-3s beforehand.
Frequently asked questions
Yes, it’s possible to take too much fish oil and krill oil. Doses of omega-3s greater than 4 g are linked to an increased risk of atrial fibrillation. What’s more, a higher intake of DHA can raise LDL cholesterol in some cases. Very high doses of fish and krill oil can cause stomach upset, heartburn, and diarrhea.
Yes, algal oils may be a good alternative to fish and krill oil. These supplements are made from microalgae. Since they’re low on the food chain, they contain fewer contaminants. Microalgal oils are good sources of omega-3s for those on a plant-based diet. They may be a good option for vegetarians and vegans.
Yes, fish, krill, and algal oils can all go bad. Recent data shows that many omega-3 supplements are at least partially oxidized at the time of purchase. Supplements with added flavoring are more likely to be oxidized than unflavored supplements. It’s important to use all supplements before their expiration date and within 6 months of opening. Also, check oils for a rancid smell and cloudiness.
Yes, it’s possible to take too much fish oil and krill oil. Doses of omega-3s greater than 4 g are linked to an increased risk of atrial fibrillation. What’s more, a higher intake of DHA can raise LDL cholesterol in some cases. Very high doses of fish and krill oil can cause stomach upset, heartburn, and diarrhea.
Yes, algal oils may be a good alternative to fish and krill oil. These supplements are made from microalgae. Since they’re low on the food chain, they contain fewer contaminants. Microalgal oils are good sources of omega-3s for those on a plant-based diet. They may be a good option for vegetarians and vegans.
Yes, fish, krill, and algal oils can all go bad. Recent data shows that many omega-3 supplements are at least partially oxidized at the time of purchase. Supplements with added flavoring are more likely to be oxidized than unflavored supplements. It’s important to use all supplements before their expiration date and within 6 months of opening. Also, check oils for a rancid smell and cloudiness.
The bottom line
Overall, fish oil has more evidence backing its protective effects on heart health than krill oil. Talk with a healthcare professional to find out if you need an omega-3 supplement and which one might be right for you. Remember, if you’re able to get enough omega-3s through your diet, that is recommended over taking supplements.
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References
Alkhedhairi, S. A., et al. (2022). The effect of krill oil supplementation on skeletal muscle function and size in older adults: A randomised controlled trial. Clinical Nutrition.
American Heart Association. (2022). Consuming about 3 grams of omega-3 fatty acids a day may lower blood pressure.
Backes, J. M., et al. (2014). Krill oil for cardiovascular risk prevention: Is it for real? Hospital Pharmacy.
Chang, M. X., et al. (2020). Astaxanthin and its effects in inflammatory responses and inflammation-associated diseases: Recent advances and future directions. Molecules.
Cholewski, M., et al. (2018). A comprehensive review of chemistry, sources and bioavailability of omega-3 fatty acids. Nutrients.
Colletti, A., et al. (2021). Advances in technologies for highly active omega-3 fatty acids from krill oil: Clinical applications. Marine Drugs.
ConsumerLab.com. (2010). ConsumerLab.com finds quality problems with nearly 30% of fish oil supplements reviewed; "Fishy" claims identified -- Softgels and liquids for adults, children and pets tested, including krill oil and algal oil supplements.
Cooperman, T. (2019). Is fish oil safe? Is it contaminated with mercury and PCBs? ConsumerLab.com.
Cooperman, T. (2020). What is the difference between fish oil and krill oil? Is one better than the other? ConsumerLab.com.
Curfman, G. (2021). Omega-3 fatty acids and atrial fibrillation. JAMA.
Gaba, P., et al. (2022). Prevention of cardiovascular events and mortality with icosapent ethyl in patients with prior myocardial infarction. Journal of the American College of Cardiology.
George, M., et al. (2022). Blood pressure–lowering effects of omega-3 polyunsaturated fatty acids: Are these the missing link to explain the relationship between omega-3 polyunsaturated fatty acids and cardiovascular disease? JAMA.
Hu, Y., et al. Marine omega-3 supplementation and cardiovascular disease: An updated meta-analysis of 13 randomized controlled trials involving 127 477 participants. Journal of the American Heart Association.
Mocking, R. J. T., et al. (2020). Omega-3 fatty acid supplementation for perinatal depression: A meta-analysis. The Journal of Clinical Psychiatry.
Mozaffarian, D., et al. (2006). Fish intake, contaminants, and human health: Evaluating the risks and the benefits. JAMA.
National Center for Health Statistics. (2021). Dietary supplement use among adults: United States, 2017-2018. Centers for Disease Control and Prevention.
Office of Dietary Supplements. (2022). Choline: Fact sheet for consumers. National Institutes of Health.
Office of Dietary Supplements. (2023). Omega-3 fatty acids: Fact sheet for health professionals. National Institutes of Health.
Pereira, C. P. M., et al. (2020). Antioxidant and anti-inflammatory mechanisms of action of astaxanthin in cardiovascular diseases (Review). International Journal of Molecular Medicine.
Stonehouse, W., et al. (2022). Krill oil improved osteoarthritic knee pain in adults with mild to moderate knee osteoarthritis: A 6-month multicenter, randomized, double-blind, placebo-controlled trial. The American Journal of Clinical Nutrition.
Tsoupras, A., et al. (2022). Cardio-protective properties and health benefits of fish lipid bioactives; the effects of thermal processing. Marine Drugs.
Ulven, S. M., et al. (2010). 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.
Ulven, S. M., et al. (2015). Comparison of bioavailability of krill oil versus fish oil and health effect. Vascular Health and Risk Management.
