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Krill Oil vs. Fish Oil vs. Fish: Which is Best?

Krill Oil vs. Fish Oil vs. Fish: Which is Best?

How to assess the different options for reaping the benefits of omega-3 fatty acids from fish.

We recently covered the importance of keeping omega-3 and omega-6 fatty acids in proper balance. For many of us supplementing with fish oil will be part of our health regimen—especially given recent studies that all but confirm the benefits of fish oil supplementation, especially for heart health. There are many options available on the market for fish oil products, including krill oil. How should consumers decide between these products?

Some experts say that eating fish is the best way to get omega-3s. They argue that concerns about toxins in fish have been overblown and have scared many people away from consuming a healthy food. Many people, for example, have been warned about the mercury content of fish. But most fish also contain plentiful selenium, which binds with mercury and blocks the body from absorbing it, thus preventing the adverse effects of mercury toxicity. We’ve also been told about other contaminants in fish like PCBs and dioxins. But the highest dietary sources of PCBs and dioxins are not fish, but beef, chicken and pork (34%), dairy products (30%) and vegetables (22%). Fish constitute only 9% of our dietary intake of these chemicals. PFAS contamination is also an issue. This contamination has mostly been linked with freshwater fish, which include salmon and trout.

Given this information, here are some pointers for which fish to eat and which to avoid. Avoid larger species like tuna, swordfish, mahi mahi, or shark. They live longer and are predatory, which increases the likelihood of accumulating harmful toxins. To avoid PFAS contamination, avoid freshwater fish like salmon, trout, or catfish. Smaller saltwater fish that are the safest bet and include fish like anchovies, mackerel, or sardines.

Avoiding certain species can minimize the risk of eating fish. With that said, fish oil supplements appear to contain almost no mercury and, at worst, only trace amounts of PCBs, which is unavoidable since PCBs are found in water everywhere. Many contaminants in fish are removed during the purification process used to make fish oil supplements. Reputable companies submit their fish oil products to rigorous purity testing from independent third parties like the International Fish Oil Standards program.

Fish oil has the benefit of being much more widely studied than krill oil. There are some helpful guides available online to help you select a quality fish oil product. One key issue with fish oil is to ensure that it is fresh and not rancid—that is, that the fish oil has not been oxidized, which would cause inflammation in the body. A good way to check on the freshness of a fish oil supplement is to request a Certificate of Analysis (COA) from the manufacturer, an analysis performed by an independent lab to measure the ingredients of a product and confirm whether it lives up to the claims made by the manufacturer. The peroxide value on the COA will measure rancidity reactions that have occurred during storage and should be less than 5 meq/kg. If you don’t want the hassle, fish oil capsules should smell like the ocean but not like rotten fish; also beware of lemon scents which can be used to mask rancidity. Natural fish oil products, as opposed to processed products, will contain additional nutrients like vitamins A and D and tend to be better absorbed than purified fish oils.  Note that fish oil should be refrigerated after opening the bottle to maintain freshness and quality and to slow the process of oxidation. Vitamin E and rosemary are regularly added to fish oils to protect from rancidity.

Krill oil, which comes from tiny, shrimp-like creatures, contains the same omega-3 fatty acids as fish oil, but there are some key differences. Because they are bottom-feeders, krill are less of a concern for contaminants, since they eat phytoplankton instead of other contaminated fish. Krill oil has EPA and DHA in smaller amounts than fish oil, and  they come in the form of phospholipids, whereas in fish oil these fatty acids are in the form of triglycerides. Some studies have suggested that the phospholipid form of omega-3’s are better absorbed by the body. In one study, blood concentrations of EPA and DHA were higher in those who took krill oil over 72 hours compared to fish oil. Some experts reviewing the evidence have concluded, however, that there isn’t enough evidence to demonstrate that krill oil is better absorbed by the body, so there is some controversy over the point of bioavailability.

EPA and DHA are both beneficial but offer different benefits. This is why you’ll see products with a variety of ratios of EPA to DHA. Generally speaking, EPA is anti-inflammatory, and DHA supports cognitive health, neurological development, and protection against neurodegenerative disease.

Another study found that krill oil was more effective than fish oil for the reduction of glucose, triglycerides, and LDL levels.

Krill oil also contains astaxanthin, a carotenoid that gives krill their red color and is a potent antioxidant that boosts the immune system, reduces inflammation, protects the skin from UV damage, and supports brain and heart health.

Proponents of krill oil further argue that it is less prone to contamination from heavy metals like mercury because krill feed on phytoplankton rather than contaminated fish.

Some evidence suggests that krill oil has a unique ability to help with joints. In an animal study, krill oil—but not fish oil—decreased inflammatory cells to the joints and cartilage. A study of arthritic patients found that krill oil significantly inhibited inflammation and arthritic symptoms in as little as seven days.

Note, too, that there is a fish oil drug on the market, Vascepa, which only contains the EPA omega-3 fatty acid. Taking this product will mean you’re missing out on the many benefits of DHA, which is brain protective, anti-inflammatory, reduces the risk of pre-term births, supports muscle recovery after exercise, and more.

So which is better? It seems like the jury is still out, though early evidence indicates that krill oil is better for those who want to lower total cholesterol or improve joint pain. Both products deliver important omega-3 fatty acids that are crucial to health, including heart health, eye health, healthy skin, pregnancy benefits, bone health, allergy benefits, and more.

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4 thoughts on “Krill Oil vs. Fish Oil vs. Fish: Which is Best?

  • The Cochrane Collaboration is pretty clear on fish oil; while there are a few trials with positive results, the meta-analytical results are consistently disappointing – unlike the consistent link between fish consumption and positive health outcomes. Why the discrepancy?

    It really doesn’t matter much what form of omega 3’s you eat, whether free fatty acids, esters, triglycerides or phosphatidyl phospholipids. And the source doesn’t matter either; fish, seaweed, krill or seal blubber, because all of these will deliver similar amounts of omega 3 HUFA’s into the bloodstream. There are strong teleological / evolutionary reasons for this; if we weren’t good at digesting fats, we probably would not have survived as a species.

    Getting into the bloodstream, however, is only primary bioavailability; you need to get them into the cell membranes in the peripheral tissues, which is where they exert their anti-inflammatory actions. That is secondary bioavailability, and to achieve this you need the right chaperones. These are the amphiphilic polyphenols – originally in seaweeds, alternatively from olive.

    These important compounds do two things; they protect the HUFA’s from oxidation in the marine food webs (and in the bloodstream), ensuring high efficiency delivery of the HUFA’s to the cell membranes, and once there they act as complimentary anti-inflammatory agents.


  • Maria

    Krill depletion for human consumption and shrimp/salmon farms is creating havoc in the marine enviornment. Whales, seals, penguins and other marine species depend on krill for survival. Penguins that can’t find food can’t feed their young, and populations crash. Some 30,000 penguin nest failures occured in just one year while krill had been vacuum-suctioned and ship-processed. Meanwhile, baleen whales returning to cold waters to feed havd found sufficient krill is no longer there – the ships have vacuumed out the krill for sale to humans or pellets for shrimp and salmon. UNSUSTANABLE: 4-5 pounds of krill are required to create/prcess ONE POUND of shrimp and salmon meal/pellets for commercial fisheries. Krill is the main prey food for many baleen whale species, penguins, seabirds, and other marine organisms. We must stop the harvest of krill and allow marine species to recover. We must stop eating salmon and shrimp, and halt the sale of krill and krill oil products. We don’t need to create more oceanic destruction.

  • Maria

    Stop the sale of krill! Krill harvesting’s dirty secret: Harvesting krill is driving extinctions:
    4-5 lbs of krill are harvested to make 1 lb. of shrimp and salmon meal/pellets for shrimp/salmon farms! Penguin/whale/seabirds… populations are crashing- they need the krill. Krill is sucked out of the ocean on huge factory ships- UNSUSTAINABLE. Say NO to KRILL! Save penguins and whales!!!

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