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Krill Oil (vs. Fish Oil): Benefits, Dosage & Side Effects

Written by Aleksa Ristic, MS (Pharmacy) | Last updated:
Jonathan Ritter
Puya Yazdi
Medically reviewed by
Jonathan Ritter, PharmD, PhD (Pharmacology), Puya Yazdi, MD | Written by Aleksa Ristic, MS (Pharmacy) | Last updated:

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Oil supplements

Krill oil is a great source of omega-3 fatty acids EPA and DHA. It can improve blood lipids, help with diabetes, and protect the eyes and joints. It offers similar benefits to fish oil and certain advantages, but there are important limitations to consider. Keep reading to learn more about krill oil benefits, safety profile, and optimal doses.

What is Krill Oil?

Krill oil is extracted from Antarctic krill (Euphausia superba), a small shellfish similar to shrimp [1].

Krill can be made into oil, powder, and protein concentrate products. Krill oil is a sustainable source of omega-3s; it is high in protein and low in saturated fat [1, 2].

People use it for high blood lipids, heart health, cognitive and mental improvement, immunity, and more. Results from animal studies provide valuable information on this supplement, but clinical evidence is limited [1].

Components

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 [2].

In whole krill, omega-3s (primarily EPA and DHA) are 19% of its total fat [2].

The phospholipids (fats with a phosphate group) in krill oil protect membranes from free radicals and prevent cell damage [3].

Other fatty acids in krill oil include [4]:

  • Myristic acid
  • Palmitic acid
  • Stearic acid
  • Behenic acid

Vitamins and Antioxidants

Krill oil also contains Vitamin A, Vitamin E, Vitamin B9 (folate), and Vitamin B12 [2].

Krill oil also contains choline, which transports fats and reduces homocysteine [1].

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 [2].

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 [1].

Omega-3 consumption restores normal endocannabinoid system function [1].

In rats, krill oil reduces high endocannabinoid levels, endocannabinoid receptor activity, and fat accumulation [1].

Although reduced endocannabinoid activity in the brain can be harmful, krill oil does not cause any negative cognitive effects [1].

Inflammatory Cytokines

Omega-3s, especially EPA, lowers inflammatory cytokines IL-1β and TNF-α, making krill oil anti-inflammatory [5].

Health Benefits

Possibly Effective:

1) Blood Lipids

In a meta-analysis of 7 trials and 662 participants, krill oil supplementation (1-3 g daily) significantly reduced LDL (-15.52 mg/dL) and increased HDL (+6.65 mg/dL) cholesterol; it also reduced triglycerides (-14.03 mg/dL). The effects on total cholesterol were insignificant [6].

Krill oil reduced cholesterol in healthy rats, rats with high levels of fat in the blood, and rats fed a high-cholesterol diet [1, 7].

Compared to fish oil, the level of clinical evidence is still insufficient for any definite conclusions.

2) Arthritis

In one study of 90 heart disease and/or arthritis patients, daily krill oil reduced joint pain (38%), stiffness (39%), and functional impairment (36%) [3].

In another study of 50 patients, krill oil improved mild knee pain and range of motion [8].

Omega-3s from krill oil reduced inflammatory cytokine levels and helped prevent arthritis in a study on mice [9].

In another mouse study, it reduced arthritis symptoms and development but did not lower inflammatory cytokines [9].

3) Diabetes

In a trial of 120 patients with high blood lipids, krill oil (1-3 g) daily significantly improved lipid profile and reduced blood glucose [10].

In 48 participants with type 2 diabetes, krill oil reduced insulin resistance after four weeks [11].

It reduced blood glucose levels and improved glucose tolerance and insulin sensitivity in a couple of animal studies [12, 13].

4) Dry Eye

Low omega-3 intake was associated with dry eye disease (eye pain and vision loss) in a study of 32,000 women [14].

In a trial of 54 participants, krill oil reduced dry eye symptoms, inflammation, and eye redness. Further research is warranted [14].

Insufficient Evidence:

No valid clinical evidence supports the use of krill oil for any of the conditions in this section. Below is a summary of up-to-date animal studies, cell-based research, or low-quality clinical trials which should spark further investigation. However, you shouldn’t interpret them as supportive of any health benefit.

5) Inflammation

In a study of 90 heart disease and arthritis patients, krill oil reduced C-reactive protein, a major marker of inflammation [3].

Krill oil lowers TNF-α (inflammation marker) in mice fed a high-fat diet [15, 1].

In rats with colitis, krill oil reduced oxidative damage and colon inflammation [16].

Astaxanthin in krill oil blocks nitric oxide and TNF-alpha production. However, astaxanthin levels in krill oil may be too low to provide health benefits [1, 3, 2].

6) Cognitive Function

Omega-3s from krill oil help protect the brain. DHA is essential for brain development and EPA improves behavior and mood [17].

Phospholipids from krill oil have antioxidant and anti-inflammatory properties. They reduce oxidative damage in the brain and help prevent cognitive decline and mental disorders [17, 18].

In a study of 45 elderly males, krill oil enhanced the function of brain areas that perform calculations and working memory tasks. The authors underlined higher phospholipid content as a potential advantage of krill over fish oil. However, the clinical significance of these results is not clear [19].

7) PMS

In a study of 70 young women, krill oil significantly reduced pain and improved the emotional symptoms of PMS, such as stress, depression, and irritability [20].

More research is needed to verify the beneficial effects of krill oil on PMS symptoms.

Krill Oil vs. Fish Oil

1) Better Absorption

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 [21, 22].

2) Better Nutrient Profile

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 while triglycerides do not [23].

Additionally, the phospholipids in krill oil protect membranes from free radicals and prevent cell damage [3].

Krill oil also contains astaxanthin, a pigment that protects the unsaturated bonds in EPA and DHA from oxidative damage [2, 24].

3) Other

People commonly complain about the large size of fish oil capsules. Krill oil capsules are smaller and more suitable for people with difficulty swallowing [25].

Additionally, the major concern of fish oil is its mercury content. Krill oil is generally cleaner and less polluted than fish oil, but this greatly depends on the source and product manufacturer [26, 27].

Drawbacks

Krill oil is more expensive than fish oil because it must be immediately processed to prevent spoiling [25].

Given this risk of spoiling and the lack of rigorous safety controls, krill oil quality might not be as good as prescription fish oil [25].

Additionally, krill oil is relatively new on the market. It has less clinical evidence backing up the health benefits and a less known safety profile. The American Heart Association does not yet recognize krill oil as an omega-3 supplement [25, 24].

Krill Oil Side Effects & Precautions

Krill oil is possibly safe in doses up to 4 grams, when used up to 3 months. Common side effects are mild and include [28, 29]:

Precautions

People who are allergic to crustaceans and shellfish (shrimp/crabs) may experience adverse reactions [6].

Storage can cause krill shells to increase fluoride levels and their effects on human health are not clear yet [30].

Drug Interactions

Supplement-drug interactions can be dangerous and, in rare cases, even life-threatening. Always consult your doctor before supplementing and let them know about all drugs and supplements you are using or considering.

Krill oil might increase the effectiveness of blood thinners and may, in theory, increase the risk of bleeding [6, 31].

Gene Interactions

In mice, krill oil decreases genes responsible for liver glucose production (SLC2A2 and PCK1). However, it did not decrease blood glucose levels [32].

Krill oil also affects genes involved in body fat production [33].

Increased

Decreased

Food Sources and Supplementation

Dosage

The below doses may not apply to you personally. If your doctor suggests using krill oil, work with them to find the optimal dosage according to your health condition and other factors.

Currently, there is no recommended dose for krill oil. Safe and effective doses in clinical trials ranged from 1-3 g daily [3, 6].

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 ranges between 180 and 250 mg EPA and DHA (combined) per capsule [24, 1].

User Reviews

The opinions expressed in this section are solely from the users who may or may not have a medical background. SelfDecode does not endorse any specific product, service, or treatment. Do not consider user experiences as medical advice. Never delay or disregard seeking professional medical advice because of something you have read on SelfDecode.

Users report positive results with krill oil for hormonal issues, joint pain, PMS, weight loss, heart health, and more. Some claim it’s more effective than fish oil and doesn’t cause bloating and fish burps.

On the other hand, some folks still complain about these side effects and can’t tell a difference between krill and fish oil.

About the Author

Aleksa Ristic

Aleksa Ristic

MS (Pharmacy)
Aleksa received his MS in Pharmacy from the University of Belgrade, his master thesis focusing on protein sources in plant-based diets. 
Aleksa is passionate about herbal pharmacy, nutrition, and functional medicine. He found a way to merge his two biggest passions—writing and health—and use them for noble purposes. His mission is to bridge the gap between science and everyday life, helping readers improve their health and feel better.

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