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As discussed in's review of omega-3 supplements, both fish oil and krill oil can provide significant amounts of the omega-3 fatty acids EPA and DHA. Overall, there are more clinical studies investigating the effects of fish oil, however, preliminary studies indicate that krill oil, like fish oil, has a beneficial effect on cholesterol and triglyceride levels, as well as anti-inflammatory effects.

Krill oil supplements, are generally a much more expensive source of EPA and DHA. It would not be unusual to spend 50 cents or more for dose of krill oil providing the same amount of EPA and DHA available from fish oil for as little as 5 to 10 cents.

Perhaps due to the higher cost, krill oil capsules tend to be much smaller than fish oil capsules and provide smaller amounts of EPA and DHA. (Be aware that some products labeled "krill oil" may actually contain a mixture of krill and fish oil.) One might justify the higher cost of krill on the basis of it containing phospholipids, which may enhance absorption, and the red-colored antioxidant astaxanthin. However, absorption of EPA and DHA from krill has not definitively been shown to be better from fish oil (at best, it may be 30% to 100% greater), and the benefit of astaxanthin is not clear. That is, even if you absorbed twice as much EPA and DHA from krill oil, that would not seem to justify paying ten to twenty times as much for it. Also, as noted in our tests of popular omega-3 supplements, krill oil supplements cannot be tested for spoilage the same way that fish oil supplements are tested, since the deeply colored astaxanthin can interfere with the results.

Both fish oil and krill oil supplements have been reported to have similar side effects, although one study found that krill oil caused more frequent gas/bloating and flatulence. Also, be aware that while some evidence suggests that fish oil may modestly improve insulin sensitivity, one study suggests that high doses (5,000) of krill oil (combined with modest amounts of salmon oil) may reduce insulin sensitivity.

For more about the evidence for fish and krill oil supplements, plus our tests and cost comparisons of popular products, see the Fish Oil and Omega-3 and -7 Supplements Review (Including Krill, Algae, Calamari, and Sea Buckthorn) and our Top Picks among products.

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September 22, 2018

Summary of research: No reason to buy krill oil. More expensive, more flatuence and krill oil is more difficult to test for quality because of red color from astaxanthin.

Pro tip: Astaxanthin 6mg, 10mg and 12mg softgels are extremely cheap to buy separately so there is absolutely no point to buy krill oil if one need benefits of Astaxanthin.

Several astaxanthin human studies can be fount at PubMed website.

February 3, 2016

I am concerned about taking fish oils because of heavy metal content. It's all so confusing!
February 3, 2016

Hi Mary - tests fish oil and other omega-3 fatty acid supplements for contamination with heavy metals including mercury, lead, cadmium and arsenic. Also see the section "Contaminants in Fish vs. Supplements" for more information:

February 3, 2016

Heavy metal if just the beginning ,there is also PCB's. What is a body to do?
February 3, 2016

Hi Herb - also tests for PCBs. You can read more about this here: You can find the results of our tests for PCBs as well as heavy metals in popular fish oil and omega-3 fatty acid supplements in the fifth column of the results table:

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