Krill are shrimp-like marine crustaceans found in all oceans of the world. Commercial fishing of krill is conducted mainly in the Southern Ocean and in waters around Japan. Krill has been traditionally harvested to be used as bait or as feed for fish farms, however, a small proportion is now harvested for its oil. Two important nutrients found in this oil are omega-3 fatty acids and astaxanthin

Like fish oil, krill oil is rich in the omega-3 fatty acids eicosapentaenoic acid, EPA, and docosahexaenoic acid, DHA. EPA and DHA are important structural components of the brain, nerves and retina and they are precursors of anti-inflammatory hormone-like substances. As discussed by researchers E.M. Roth and W.S. Harris from the University of Cincinnati, omega-3 fatty acids protect against heart disease–they recommend that people with coronary heart conditions take 1g of EPA plus DHA daily and people with high blood triglycerides should take 1 to 4 g daily.

The potent anti-inflammatory properties of omega-3 fatty acids also make them a beneficial nutrient for people suffering from conditions characterized by excess inflammation. According to R. Wall and colleagues at the Alimentary Pharmabiotic Centre, Ireland, omega-3-rich foods can help reduce the risk of rheumatoid arthritis, inflammatory bowel disease and cancer.

Astaxanthin is a carotenoid anti-oxidant and thus helps protect against the damage caused by free-radical molecules. According to R.G. Fassett and J.S. Coombes, researchers from the University of Queensland, Australia, astaxanthin can reduce oxidative stress and inflammation and may thus protect against cardiovascular disease. Fassett and Coombes also report that up to July 2009, all studies have shown that dietary supplementation with astaxanthin is not associated with any adverse effects.

F. Sampalis and colleagues at the University of Montreal, Canada, carried out a study investigating the effectiveness of krill oil for the management of premenstrual syndrome and dysmenorrhea. Dysmenorrhea is characterized by severe uterine pain during menstruation. In this study, 70 patients diagnosed with premenstrual syndrome were given either krill oil or fish oil for three months. It was found that the number of analgesics used for dysmenorrhea within the krill oil group was lower than that in the fish oil group. F. Sampalis and colleagues thus concluded that krill oil can significantly reduce dysmenorrhea and the emotional symptoms of premenstrual syndrome. Krill oil reduced symptoms better than fish oil.