Fish oil comes from oily fish, such as tuna, herring, or sardines. Krill oil comes from a small, shrimp-like animal called krill.
Krill oil has a distinctive red color, while fish oil supplements are typically yellow or gold. Krill oil is usually more expensive than fish oil.
While each supplement type contains omega-3 fatty acids, taking each supplement type presents various risks and benefits. Read on to find out more.
Benefits of krill oil and fish oil
Omega-3 fatty acids are present in krill oil and fish oil.
Both krill oil and fish oil contain omega-3 fatty acids. Some of the most popular and beneficial omega-3 fatty acids are eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
However, while research has shown eating whole fish can have heart-protecting benefits, scientific studies have not yet proven that taking omega-3 supplements offers the same benefits as eating fish.
The National Institutes of Health (NIH) state that the specific benefits of taking omega-3 supplements include:
- Reducing high triglyceride levels. High triglyceride levels have links to an increased risk for heart disease.
- Relieving rheumatoid arthritis. Evidence suggests that omega-3 supplements may help relieve the symptoms of rheumatoid arthritis.
- Relieving dry eye symptoms. Some people use omega-3 supplements to help improve eye moisture and reduce the symptoms of dry eye disease. However, large-scale studies have found that taking omega-3 supplements are no better than a placebo for eye dryness, so more research is necessary.
What does the research say?
A study from 2011 compared the effects of fish and krill oil, finding that they resulted in similar blood levels of EPA and DHA. However, people took 3 grams (g) of krill oil and only 1.8 g of fish oil, which may suggest that a person needs to take almost twice as much krill oil as fish oil to get the same benefits.
According to the study's authors, 30–65 percent of krill oil's fatty acids are stored as phospholipids, while the fatty acids in fish oils are instead stored primarily as triglycerides.
The researchers suggest that the body may able to use fatty acids stored as phospholipids more easily. However, despite this possibility, a person may still have to take more krill oil capsules than fish oil to get an equivalent amount of omega-3s.
The amount and concentration of omega-3 in krill and fish oil also vary depending on the product. Some krill oil manufacturers claim that the krill oil omega-3s are better absorbed than fish oil omega-3s, so a lower concentration works just as well. However, there is no current proof that this statement is true.
Another small-scale study published in 2013 found that after 4 weeks of taking only one of the supplements, krill oil led to higher levels of EPA and DHA in a person's blood compared with fish oil. Although both supplements increased levels of healthful omega-3 fatty acids, they also increased levels of low-density lipoprotein (LDL) cholesterol, which is the 'bad' cholesterol.
Studies are not consistent, though. A study from 2015 found no differences in krill oil and fish oil in the blood after 4 weeks of taking supplements.
While some research suggests that the body might better absorb krill oil, other studies find no difference between fish and krill oil. More research is therefore needed.
The above research only looks effects of the oil on blood levels, which is just one marker of their potential benefits. No study has compared these products to see if one works better than the other for the specific uses that people are interested in, such as bodybuilding or promoting heart health.
Risks of krill oil and fish oil
Omega-3 supplements present no significant risks, but a person may experience bad breath as a result.
Taking omega-3 supplements in the forms of krill oil and fish oil does not appear to carry any significant side effects.
Minor side effects may include:
Also, omega-3 supplements, such as krill oil and fish oil, have the potential to interact negatively with blood-thinning medications, such as warfarin (Coumadin).
This is because omega-3 fatty acids have mild anticoagulant or blood-thinning effects. However, a person must usually take between 3 and 6 g of fish oil a day for these adverse interactions to occur.
The Office of Dietary Supplements (ODS) advises no established upper limit for taking omega-3 supplements. However, taking dosages of more than 900 milligrams (mg) of EPA and 600 mg of DHA a day can reduce a person's immune system by suppressing natural inflammatory responses.
According to the ODS, daily intakes for omega-3 fatty acids are about 1.6 g per day for men and 1.1 g per day for women.
The ODS also recommend not exceeding 2 g of EPA and DHA a day from dietary supplements. A person should read supplement labels carefully to determine how much of each substance is in each capsule.
Omega-3 may help to reduce rheumatoid arthritis symptoms.
According to the ODS, an estimated 7.8 percent of adults and 1.1 percent of children in the United States take omega-3 fatty acid supplements in the forms of fish oil, krill oil, or animal-free alternatives, such as algal oil or flaxseed oil.
The evidence is still inconclusive about whether krill oil works as well as or better than fish oil. So far, most of the research on the benefits of omega-3 fatty acids has been carried out using fish oil. Not a lot of research is currently available on krill oil.
Taking omega-3 supplements can offer benefits in terms of lowering triglyceride levels and reducing rheumatoid arthritis symptoms. However, the evidence is inconclusive regarding whether they can reduce heart disease or improve overall cardiovascular health to the same extent as eating whole fish.
According to the NIH, eating oily fish, including tuna and salmon, can offer a greater variety of nutrients than supplements and has demonstrated improvements in heart health.
On balance, taking either krill oil or fish oil supplements can help boost a person's overall levels of omega-3 fatty acids, though whether one is better than the other is currently unclear.
What are the best supplements for heart health?
Getting your daily nutritional needs from a healthful diet is always the healthiest option.
A person can take supplements in addition to healthy dietary choices and nutrient-dense foods. They should not use supplements as a replacement for nutritious meals.
People with heart disease may benefit from an omega-3 fatty acid supplement if diet alone is not sufficient. As always, consult a healthcare professional before beginning any new supplement.Katherine Marengo LDN, RD Answers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.