Krill are tiny, shrimp-like crustaceans that flourish in the Antarctic Ocean and provide food for numerous aquatic animals. Oil made from krill has come on the market as an alternative to fish oil. Like fish oil, krill oil contains the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Krill also contains omega-6 fatty acids, an antioxidant in the carotenoid family called astaxanthin, and substances called phospholipids.

Requirements/Sources

Many grains, fruits, vegetables, sea vegetables, and vegetable oils contain significant amounts of essential fatty acids, but krill oil is an especially rich source.

Carotenoids are also found in many foods, especially yellow/orange and dark green fruits and vegetables. They are not essential nutrients (except insofar as some can be converted to vitamin A), but they might offer some health benefits.

Phospholipids are utilized in the body for numerous purposes, but they are not essential nutrients.

Dosage

A typical recommended dose of krill oil is 1-3 g daily.

Therapeutic Uses

Based on its omega-3 fatty acid content, krill oil would be expected to have many of the same effects as fish oil. See the full Fish Oil article for a detailed discussion of these potential benefits.

A few studies have evaluated krill oil specifically. In one double-blind, placebo-controlled study, 120 people with high cholesterol were given krill oil, fish oil, or placebo.1 The results over 3 months showed that krill oil (taken at a dose ranging from 1-3 g daily depending on body mass and which group the participants were assigned to) improved all aspects of cholesterol profile as compared to placebo, and it was more effective than fish oil (taken at the fixed dose of 3 g daily). Krill oil also reduced blood sugar levels. However, in a subsequent trial involving 113 subjects with normal or slightly elevated cholesterol levels, there was no difference in cholesterol changes between the groups receiving 3 g daily of krill oil and 1.8 g daily of fish oil for 7 weeks. A possible explanation for these differing results is that krill and fish oils are only effective in reducing cholesterol levels when the levels are significantly elevated.5

Another double-blind study compared krill oil against fish oil for treatment of symptoms of premenstrual syndrome (PMS) and dysmennorhea (menstrual cramps).2 This study suffered from many problems in design and reporting, but appeared to show that krill oil was more effective than fish oil for treating both of these conditions.

A badly designed study hints that krill oil might be helpful for both osteoarthritis and rheumatoid arthritis.4

Safety Issues

Based on its known constituents, krill oil would be expected to have little to no toxicity. Side effects seen in studies are limited to occasional digestive distress and allergic reactions. The only known potential concerns relate to possible blood-thinning effects: Fish oil is known to decrease blood coagulation, and in one case report it increased the effect of the blood-thinning medication warfarin (Coumadin).3 People who are at risk of bleeding complications for any reason should consult a physician before taking krill oil. Maximum safe doses in young children, pregnant or nursing women, or people with severe liver disease have not been established.