Fish oil
Fish oil is oil extracted from fish tissues, especially oily fish. It is rich in the long-chain omega-3 fatty acids EPA and DHA.
Eicosapentaenoic acid: A long-chain omega-3 fatty acid, abbreviated EPA, found in fish and marine oils. EPA is one of the principal fatty acids that gives fish oil its nutritional profile.
Fish oil supplement: A dietary supplement made from fish oil, usually providing EPA, DHA, or both. This is the most familiar concentrated form in which fish oil is consumed.
Eicosanoid: A signaling molecule made from polyunsaturated fatty acids, including prostaglandins and leukotrienes. EPA competes with arachidonic acid as a precursor for several eicosanoid pathways.
Krill oil: Oil extracted from krill, small marine crustaceans, containing omega-3 fatty acids and phospholipids. It is marketed as an alternative marine omega-3 source with a different lipid composition.
REDUCE-IT: A clinical trial that found fewer cardiovascular events with purified EPA in selected high-risk patients. Its positive result raised questions about whether purified EPA differs from mixed fish-oil products.
Docosahexaenoic acid: A long-chain omega-3 fatty acid, abbreviated DHA, abundant in brain and retinal membranes. DHA is the other principal omega-3 fatty acid supplied by many fish oils.
Cod liver oil: Oil extracted from the livers of cod and related fish, containing omega-3 fats and vitamins A and D. It is a distinct fish-oil product whose vitamin content matters alongside its omega-3s.
Arachidonic acid: An omega-6 fatty acid abundant in cell membranes and a precursor to eicosanoids. Its shared enzymes and signaling pathways help explain how EPA can alter lipid mediator production.
Algal oil: Oil produced from algae, often containing DHA and sometimes EPA. It supplies marine-type omega-3s without extracting oil from fish.
STRENGTH trial: A clinical trial of a high-dose EPA–DHA formulation that did not reduce major cardiovascular events. Its neutral result contrasts with REDUCE-IT and complicates broad claims about fish oil.