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Krill oil is a good source of the omega-3 fatty acids EPA and DHA. It can protect against heart disease, treat depression, and help prevent cancer.

Since krill oil has similar benefits to fish oil and few side effects, it is a good alternative to fish oil. Keep reading to learn more about krill oil’s health benefits and its comparison to fish oil.


Krill oil is extracted from Antarctic krill (Euphausia superba), a small shellfish similar to shrimp [R].

Krill can be made into oil, powder, and protein concentrate products. Krill oil is a sustainable source of omega-3s [R].

It is high in protein and low in saturated fat [R].

Animal studies of krill oil show it can treat depression, obesity, rheumatoid arthritis, heart disease, and cancer [R].

Even though krill oil has few human studies, results from animal studies provide valuable information on this supplement [R].


Fatty Acids

The fat content of krill oil ranges from 12 to 50% of its total weight. In the spring, krill’s fat content is lower because of the lack of food and is higher in the summer and fall when food is abundant [R].

In whole krill, omega-3s (primarily EPA and DHA) are 19% of its total fat [R].

The phospholipids (fats with a phosphate group) in krill oil protect membranes from free radicals and prevent cell damage [R].

Other fatty acids in krill oil include [R]:

Vitamins and Antioxidants

Krill oil also contains Vitamin A, Vitamin E, Vitamin B9 (folate), and Vitamin B12 [R].

Krill oil also contains choline, which transports fats and reduces homocysteine [R].

Additionally, krill oil contains astaxanthin, a fat-soluble pigment and powerful antioxidant. However, astaxanthin levels in krill oil may be too low to provide health benefits [R].

Mechanisms of Action

The Endocannabinoid System

Endocannabinoids stimulate the immune system and play roles in motivation, mood, and memory. Issues with the endocannabinoid system can cause heart, weight, blood sugar problems, anxiety, depression, learning problems, and memory loss [R].

Omega-3 consumption restores normal endocannabinoid system function [R].

In rats, krill oil reduces high endocannabinoid levels, endocannabinoid receptor activity, and fat accumulation [R].

Although reduced endocannabinoid activity in the brain can be harmful, krill oil does not cause any negative cognitive effects [R].

Inflammatory Cytokines

Omega-3s, especially EPA, lowers inflammatory cytokines IL-1β and TNF-α, making krill oil anti-inflammatory [R].

Health Benefits

1) Krill Oil May Prevent Obesity

Krill oil blocks the endocannabinoid (EC) pathway, which controls appetite, promoting weight loss [R].

Mice with normal omega-3 levels have normal EC levels, while omega-3-deficient mice have higher endocannabinoid levels [R].

Krill oil raised omega-3 levels and reduced EC levels in rats [R].

Although krill oil did not affect food intake, it lowered 2-arachidonoylglycerol (2-AG), an EC involved in overeating [R, R].

Lowering EC levels reduces the likelihood of overeating, which helps prevent weight gain and obesity.

2) Krill Oil May Lower Cholesterol Levels

Krill oil reduced cholesterol in healthy rats, rats with high levels of fat in the blood, and rats fed a high-cholesterol diet [R, R].

In patients with high cholesterol, both low (1-1.5 g) and high (2-3 g) doses of krill oil decreased total cholesterol (by 13 and 18%) compared to fish oil and placebo [R, R].

3) Krill Oil Reduces Inflammation

In a study (DB-RCT) of 90 heart disease and arthritis patients, krill oil reduced C-reactive protein, a marker of inflammation [R].

Krill oil lowers TNF-α (inflammation marker) in mice fed a high-fat diet [R, R].

Astaxanthin in krill oil blocks nitric oxide production, which reduces TNF-α production. However, astaxanthin levels in krill oil may be too low to provide health benefits [R, R, R].

Lowering these markers of inflammation helps prevent oxidative damage and excessive inflammation.

4) Krill Oil Combats Arthritis

Omega-3s from krill oil reduced inflammatory cytokine levels, which helps prevent arthritis [R].

In one study (DB-RCT) of 90 heart disease and/or arthritis patients, daily krill oil reduced pain, stiffness, and functional impairment [R].

In another study (DB-RCT) of 50 patients, krill oil improved mild knee pain and range of motion [R].

In mice genetically susceptible to arthritis, krill oil reduced arthritis symptoms and development. However, krill oil did not lower inflammatory cytokines [R].

5) Krill Oil Protects the Brain

Omega-3s from krill oil help protect the brain. DHA is essential for brain development and EPA improves behavior and mood [R].

Phospholipids from krill oil have antioxidant and anti-inflammatory properties. They reduce oxidative damage in the brain and help prevent brain disorders such as depression, schizophrenia, dementia, epilepsy, and autism [R, R].

Omega-3s in krill oil also prevent brain function decline in elderly people. In a study (DB-RT) of 45 elderly males, krill oil enhanced the function of brain areas that perform calculations and working memory tasks [R].

6) Krill Oil Improves Depression Symptoms

Seafood consumption is associated with lower rates of depression [R].

In rats, krill oil increases brain DHA levels and lowers depression-like behaviors [R].

In a study (DB-RCT) of 70 patients, krill oil improved PMS-associated depression [R].

7) Krill Oil Protects the Heart

The omega-3s in krill oil lower the rate of heart disease [R].

Additionally, krill oil:

  • Increases HDL (good) cholesterol in patients with high cholesterol [R].
  • Reduces fat and cholesterol levels in patients with high cholesterol and triglycerides [R].
  • Reduces blood pressure in rats with high blood pressure [R].
  • Reduces total blood cholesterol in rats fed high-fat diets [R].

8) Krill Oil Helps Treat Diabetes

Krill oil reduces risk factors for diabetes, such as insulin resistance and glucose levels.

Krill oil reduced blood glucose levels and improved glucose tolerance and insulin sensitivity in animal studies [R, R].

Krill oil helps reduce the risk of heart attack in diabetic patients by:

  • Improving blood tissue function
  • Lowering C-reactive protein
  • Increasing HDL (good) cholesterol [R].

In 48 participants with type 2 diabetes, krill oil reduced insulin resistance after four weeks [R].

9) Krill Oil Stops Cancer Cell Growth

In human cells, fatty acid extracts from krill oil stopped the growth of colorectal cancer cells [R].

Since krill oil extract kills cancer cells and is well-tolerated, it is a potential anti-cancer therapy [R].

10) Krill Oil Helps Dry Eyes

Low omega-3 intake was associated with dry eye disease (eye pain and vision loss) in a study of 32,000 women [R].

In a trial (DB-RCT) of 54 participants, krill oil reduced dry eye symptoms, inflammation, and eye redness [R].

11) Krill Oil Reduces PMS Symptoms

EPA and DHA lower PMS symptoms such as mood swings, fatigue, and depression [R].

In a study (DB-RT) of 70 women, krill oil reduced stress, depression, irritability, and use of pain relievers [R].

12) Krill Oil Reduces Colitis Symptoms

Colitis is the inflammation of all or part of the colon. By reducing inflammation, krill oil reduces colitis symptoms [R].

In rats with colitis, krill oil reduced oxidative damage and colon inflammation [R].

Krill Oil vs. Fish Oil

1) The Body Absorbs More Fatty Acids from Krill than Fish Oil

Krill oil provides the body with more EPA and DHA than fish oil [R, R].

In two studies of healthy volunteers (115 and 12 participants), the krill oil group absorbed more EPA than the fish oil group. However, DHA absorption was the same [R, R].

In contrast to fish oil, krill oil contains free (not bound) DHA and EPA, making them more available for the body to use [R].

2) Krill Oil Has Stronger Effects than Fish Oil

In mice, krill oil decreased arachidonic acid (an indicator of inflammation), fatty acid production, and increased insulin sensitivity more than fish oil [R].

Krill oil also breaks down more fats in mice by blocking enzymes that promote fat creation [R].

3) Krill Oil Contains More Nutrients than Fish Oil

The EPA and DHA in krill oil are in the form of phospholipids (fats with a phosphate group), while in fish oil, they are in the form of triglycerides. Phospholipids enhance omega-3 absorption but triglycerides do not [R].

Additionally, the phospholipids in krill oil protect membranes from free radicals and prevent cell damage [R].

Krill oil also uniquely contains the antioxidant astaxanthin, a pigment that protects the unsaturated bonds in EPA and DHA from oxidative damage [R, R].

4) Other Differences

Krill and fish oil affect gene expression differently. In mice, fish oil changed the expression of 192 genes in the liver, while krill oil altered expression of 4,892 genes. This means that krill oil impacts more pathways (glucose and lipid (fat) metabolism and the energy production in mitochondria), which increases its potential for health benefits [R].

People commonly complain about the large size of fish oil capsules. Krill oil capsules are smaller and more suitable for people with difficulty swallowing [R].

Additionally, the major concern of fish oil is its mercury content. Krill oil is free of pollutants, toxins, and mercury, so consumers do not need to worry about krill oil’s safety [R, R].

Krill oil is more expensive than fish oil because it must be immediately processed to prevent spoiling [R].

Given this risk of spoiling, krill oil quality might not be as good as prescription fish oil [R].

Krill Oil Caveats and Side Effects

Compared to the large amount of human research on fish oil, there are few krill oil human trials. Additional studies are needed to determine the safety and effectiveness of krill oil on human health.

The American Heart Association does not recognize krill oil as an omega-3 supplement, so consumers should be cautious [R, R].

People who are allergic to crustaceans and shellfish (shrimp/crabs) may experience adverse reactions [R].

Storage can cause krill shells to increase fluoride levels and its effects on human health are not clear yet [R].

Common Side Effects

Common side effects include [R, R]:

Sources and Dosage


Currently, there is no recommended dose for krill oil. However, the American Heart Association recommends 250 to 500 mg of EPA + DHA each day. The amount of fatty acids in krill oil depends on the type and brand but typically range between 180 and 250 mg EPA and DHA (combined) per capsule [R, R].


Marine-based fatty acids can cause blood thinning and prevent blood from clotting. Although krill oil’s blood-thinning effects have not been tested, it shares similar fatty acids with fish oil. Hence, this side effect could still be possible [R].

Krill oil might increase the effectiveness of blood thinners and can increase the risk of bleeding. People who are taking blood thinners should not take krill oil supplements at the same time [R, R].

Gene Interactions

In mice, krill oil decreases genes responsible for liver glucose production (SLC2A2 and PCK1). However, it did not decrease blood glucose levels [R].

Krill oil also affects genes involved in body fat production [R].



  • SLC2A2
  • PCK1
  • HNF4A
  • SREBF1
  • SREBF2
  • ACADVL [R].



  • “In the past, I have always found that fish oil capsules have given me heartburn and a fishy aftertaste. After switching to Neptune Krill capsules I have not had this problem” [R].
  • “I prefer krill oil to fish oil as it helps immensely with hormone issues, bloating etc, where fish oil just made the problem worse for me” [R].
  • “Helps me tremendously with joint pain, as well as with PMS. Also, has a great supply of antioxidants” [R].
  • “One of the best because (1) you’re taking fewer capsules (2) krill oil won’t go rancid versus fish oils (3) contains astaxanthin (4) it’s Neptune Krill oil which is toxin-free. I’ve used Krill oil in the past to help me to lose weight” [R].
  • “For a person with heart disease, it is helpful for hypertension and lowering bad cholesterol. Some of the people I know that used it said it help with their memory and vision. One person said it helped their prostate.”
  • “I had to stop taking them after 3 days got stomach cramps and became very bloated it has been a week now and still hurting” [R].
  • “Don’t notice anything more than a quality fish oil” [R].

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1 Star2 Stars3 Stars4 Stars5 Stars (15 votes, average: 4.40 out of 5)


  • Dr John Warre

    As a member of Greenpeace I believe that you should leave the Krill to the whales, penguins and seals who depend on it a vital source of food. I support the setting up of an Antartic nature sanctuary to stop further exploitation.

  • carol close

    Krill oil is a high quality, sustainably harvested omega 3 fatty acid oil, rich in EPA and DHA. Krill oil omega-3s are attached to phospholipids, which make them more easily absorbed by the body than the triglyceride form of omega-3s found in fish oil, however, here is another study that says it causes leaky gut as a detrimental side effect.

    J Nutr. 2011 Sep;141(9):1635-42. Epub 2011 Jul 20.
    Ingestion of (n-3) fatty acids augments basal and platelet activating factor-induced permeability to dextran in the rat mesenteric vascular bed.
    Dombrowsky H, Lautenschläger I, Zehethofer N, Lindner B, Schultz H, Uhlig S, Frerichs I, Weiler N.
    Loss of intestinal barrier function and subsequent edema formation remains a serious clinical problem leading to hypoperfusion, anastomotic leakage, bacterial translocation, and inflammatory mediator liberation. The inflammatory mediator platelet activating factor (PAF) promotes eicosanoid-mediated edema formation and vasoconstriction. Fish oil-derived (n-3) fatty acids (FA) favor the production of less injurious eicosanoids but may also increase intestinal paracellular permeability. We hypothesized that dietary (n-3) FA would ameliorate PAF-induced vasoconstriction and enhance vascular leakage of dextran tracers. Rats were fed either an (n-3) FA-rich diet (EPA-rich diet; 4.0 g/kg EPA, 2.8 g/kg DHA) or a control diet (CON diet; 0.0 g/kg EPA and DHA) for 3 wk. Subsequently, isolated and perfused small intestines were stimulated with PAF and arterial pressure and the translocation of fluid and macromolecules from the vasculature to lumen and lymphatics were analyzed. In intestines of rats fed the EPA-rich diet, intestinal phospholipids contained up to 470% more EPA and DHA at the expense of arachidonic acid (AA). The PAF-induced increase in arterial pressure was not affected by the EPA-rich diet. However, PAF-induced fluid loss from the vascular perfusate was higher in intestines of rats fed the EPA-rich diet. This was accompanied by a greater basal loss of dextran from the vascular perfusate and a higher PAF-induced transfer of dextran from the vasculature to the lumen (P = 0.058) and lymphatics. Our data suggest that augmented intestinal barrier permeability to fluid and macromolecules is a possible side effect of (n-3) FA-rich diet supplementation.

  • carol close

    I was shocked to read that fish oil promotes brain oxidative stress and aging protein overproduction, so fish oil is bad for the aging brain. “EPA or DHA enhanced oxidative stress and aging protein expression in brain of d-galactose treated mice.”
    In conclusion, the intake of EPA or DHA in DG-treated mice decreased brain LDL and declined inflammatory pathway of AA/COX-2/PGEs. However, these two PUFAs promoted brain oxidative stress and aging protein overproduction. These findings suggest that these two PUFAs have double-sided effects toward aging brain. Therefore, the safety of EPA, DHA or foods rich in these PUFAs should be carefully re-considered.

    I was also shocked to read that fish oil causes leaky gut! “Effect of gamma-linolenic acid or docosahexaenoic acid on tight junction permeability in intestinal monolayer cells and their mechanism by protein kinase C activation and/or eicosanoid formation.” CONCLUSIONS: GLA and DHA affect tight junction permeability in intestinal monolayer cells specifically and in a concentration-dependent manner.

    Lipid Res. 2004 Aug;45(8):1418-28. Epub 2004 Jun 1.
    Lipid peroxidation induced by DHA enrichment modifies paracellular permeability in Caco-2 cells: protective role of taurine.
    Roig-Pérez S, Guardiola F, Moretó M, Ferrer R.
    Dietary enrichment with docosahexaenoic acid (DHA) has numerous beneficial effects on health. However, the intake of high doses of polyunsaturated fatty acids can promote lipid peroxidation and the subsequent propagation of oxygen radicals. The purpose of this study was to evaluate the effect of DHA on lipid peroxidation and tight junction structure and permeability in Caco-2 cell cultures. Moreover, the effects of taurine, a functional ingredient with antioxidant properties, were also tested. Differentiated Caco-2 cell monolayers were maintained in DHA-supplemented conditions with or without added taurine. Incubation with 100 microM DHA increased lipid peroxidation and paracellular permeability, in parallel with a redistribution of the tight junction proteins occludin and ZO-1. Taurine partially prevented all of these effects. The participation of reactive oxygen and nitrogen species in increased paracellular permeability was also examined using various agents that modify the formation of superoxide radical, hydrogen peroxide, nitric oxide, and peroxynitrite. We conclude that hydrogen peroxide and peroxynitrite may be involved in the DHA-induced increase in paracellular permeability and that the protective role of taurine may be in part related to its capacity to counteract the effects of hydrogen peroxide.

  • Eric Bohl

    Krill oil is produced from crustaceans so if you’re allergic to shellfish beware. I’m surprised that you didn’t mention this…

  • Vince

    Fish oil always seems to get more attention than krill oil, even though they both offer considerable benefits. I love your treatment of the topic here and it seems like krill oil is often overlooked when it shouldn’t be.

    To me, it seems like krill oil is somewhat safer than fish oil but has been studied less. Still, many similar compounds present, krill oil should offer a range of benefits.

  • anna burns

    I have tried many brands and dosages of krill oil, and I have never experienced any benefits from them. The same
    with fish oil. Are you supposed to feel better when you take it?

  • Adriana F Quintas

    Hi, I am a doctor and started to give Krill Oil to my husband. he had some seizures after taking it. then I researched again and there are some allergy reports regarding krill oil. I removed and seizures immediately stopped. He has usually seizures once he has intestinal issues (gluten ingestion, diarrhea, etc). so it is just a warning

  • steve

    For some reason I feel more effect from Nordic Naturals Fish Oil than Krill Oil.
    I still alternate them just in case

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