Krill Oil vs Fish Oil

Have your clients been asking about krill oil and whether it’s better than fish oil?

Krill oil supplements have been available for years but currently are marketed as a source of omega-3 fatty acids superior to fish oil. But are they really better than fish oil supplements? This article will review how krill oil differs from fish oil and what the research says about its role in health and disease prevention.

How Do They Compare With Each Other?
Krill oil is derived from krill, small crustaceans found in the ocean. They have a similar appearance to shrimp and are a dietary staple for whales, seals, and other sea life. As with fish oil, krill oil supplements are a source of omega-3 fatty acids, including EPA and DHA.

Because krill oil supplements are derived from a different source than fish oil supplements, the fat content is different. About 30% to 65% of the fatty acids in krill oil are phospholipids, whereas the fatty acids in fish oil are mainly in the form of triglycerides.

Some have proposed that the phospholipid content of krill oil improves its bioavailability or makes it easier to absorb, but research hasn’t supported this. In fact, two studies have found similar improvements in plasma EPA and DHA levels after supplementation with either krill oil or fish oil.

Krill oil also contains the antioxidant astaxanthin and vitamins D and E. Astaxanthin has been suggested to help improve HDL cholesterol levels, but further research is needed. Krill oil also provides choline, which may help to reduce homocysteine levels.

Krill oil comes in a softgel that’s typically smaller than larger fish oil softgels, making it easier for some clients to swallow. In addition, krill oil reportedly has less of a fishy taste. A disadvantage of krill oil is that it tends to be more expensive than fish oil.

Very few clinical trials have evaluated outcomes of krill oil supplementation, and even fewer have directly compared krill oil and fish oil.

A study evaluating various doses of krill oil ranging from 0.5 to 4 g daily vs olive oil found that krill oil at any dose significantly improved participants’ omega-3 index, a measure of blood levels of EPA and DHA. The study had some limitations that occurred with variability in triglyceride measurements. To increase the statistical power, researchers pooled all krill oil supplemented patients and demonstrated reduced triglyceride levels.

In another study, both krill oil and fish consumption containing similar amounts of EPA improved serum triglycerides, but krill oil performed no better than simply eating fish. Krill oil did result in lower fasting glucose levels, but those that consumed fish had greater improvement in vitamin D levels.

Only one study has found krill oil to be more effective than fish oil at reducing glucose, triglyceride, and LDL cholesterol levels.

A 2017 meta-analysis found that krill oil reduced plasma triglycerides; however, a more recent meta-analysis by Kim and colleagues concluded that the lipid-modifying effects of krill oil were no different than those of fish oil. Furthermore, the reduction in triglyceride levels appeared to be dose dependent.

Just one month ago, a pharmaceutical company that had entered phase III trials for a prescription drug candidate derived from krill oil published a press release including results of its clinical trial, which found that the krill oil reduced triglyceride levels. However, due to an unusual triglyceride reduction in the control group, there was no statistical significance between the treatment or control group. As a result, the company no longer plans to move forward to seek FDA approval.

Is Krill Oil Safe?
As with any supplements, it’s important to consider your client’s goals and the potential benefits vs risks. As with fish oil, krill oil may not be appropriate for some clients. Anyone with a seafood or fish allergy should avoid both fish and krill oil supplements.

Krill oil supplements may slow blood clotting, as fish oil supplements might. Therefore, they’re not recommended for clients with bleeding disorders or who are prescribed blood thinners. In additionally, they shouldn’t be taken for two weeks before planned surgery.

Some individuals have complained of gastrointestinal symptoms and heartburn associated with supplementation.

Omega-3 Recommendations
According to the Office of Dietary Supplements, Adequate Intakes (AI) have been established for omega-3 fatty acids and range from 1.1 to 1.6 g daily for adults, but this recommendation is only for alpha-linoleic acid (ALA), as it’s essential. No AI has been established for EPA and DHA, but the Institute of Medicine suggests that doses in excess of 900 mg/day EPA and 600 mg/day DHA may reduce immune function. Moreover, doses of more than 2 to 15 g daily may increase bleeding risk. The FDA recommends to not exceed 3 g/day combined EPA and DHA or 2 g coming solely from supplements. That said, no formal upper limits are established.

Current recommendations from the 2015–2020 Dietary Guidelines for Americans and the American Heart Association are to include 8 oz per week of fatty fish and seafood, such as salmon, mackerel, herring, sardines, albacore tuna, or bluefin tuna, in one’s diet as a source of omega-3s.

Prescription doses of fish oil, known as Vascepa and Lovaza, are available and may help reduce triglyceride levels, but they must be used under medical supervision.

RDs should modify recommendations for clients who don’t or can’t eat fish or seafood. Vegans and vegetarians or clients with fish and seafood allergy can be counseled to incorporate plant-based sources of ALA (which the body converts to EPA and DHA), such as chia seeds and flaxseeds, to reach adequate serum levels. Algae oil supplements are another option that enables these populations to obtain DHA and EPA directly.

Research on the use of krill oil is inconclusive at this time. Both krill and fish oils appear to improve EPA and DHA levels, but beyond that more research is needed. For now, choosing between the two may be a matter of affordability and personal preference.

As with any supplements, consumers should look for ones that have been tested and verified by third-party organizations such as the U.S. Pharmacopeia, NSF, or

Whether clients opt for fish oil or krill oil, these supplements shouldn’t be considered a primary therapy. Supplementation should accompany diet modifications, physical activity, and prescription medications (if needed) under the care of a physician.

— Jennifer Lefton, MS, RDN-AP, CNSC, FAND, is a freelance writer and nutrition consultant in northern Virginia. After gaining years of clinical nutrition experience in the hospital setting, she enjoys creating evidence-based content for companies, websites, and blogs. You can find Jennifer on Instagram @nutritiousknowledge.

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