Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are long-chain omega-3 fats that play important roles in neurological health, immune function, eye health and vision, inflammation, pain signaling, gut health, fetal development, and some aspects of cardiovascular health (like triglyceride levels and blood clotting). They exert many of their effects by helping form chemical messengers called prostaglandins, thromboxanes, and leukotrienes. EPA and DHA also serve as a structural component of the cell membrane, influencing important properties such as membrane fluidity and permeability. Small amounts of them can be synthesized from a shorter-chain omega-3 fat, alpha-linolenic acid (ALA).
Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), collectively referred to as long-chain omega-3 fats, have unique health properties and a fascinating history! Up through the early 1900s, dietary fat was believed to simply be a source of calories, interchangeable with carbohydrates and not required for life. But in 1929, George and Mildred Burr—a husband-and-wife research team—conducted a series of rat experiments revealing that certain fatty acids were critical to health, and their absence led to serious deficiency symptoms and even death. The Burrs subsequently coined the term “essential fatty acids,” and initially ascribed this essential nature only to the omega-6 fat linoleic acid. It took many more decades before omega-3s became recognized as essential, too! Eventually, in the 1970s, interest in omega-3 fats began skyrocketing when scientists discovered that the seafood-rich diet of the Greenland Inuit seemed to protect them from heart disease—leading to thousands of studies seeking to understand these special fats, as well as an entire industry built around selling them as supplements!
EPA and DHA are particularly important for fetal development, immune function, retinal health, inflammation, and some aspects of cardiovascular health (like triglyceride levels and blood clotting); they’re also a structural component of the cell membrane. Small amounts of them can be synthesized from a shorter-chain omega-3 fat, alpha-linolenic acid (ALA).
Rich sources of DHA and EPA are fish, particularly fatty cold-water fish (like salmon, herring, mackerel, sardines, and menhaden) as well as some algaes and cod liver oil. Shellfish such as mussels, crab, oysters, and squid also contain some long-chain omega-3s. There are also trace amounts in the leafy green vegetable purslane, although the type of omega-3 found in plant foods is more typically ALA!
This article explains the biological roles of EPA and DHA, the interactions between dietary EPA and DHA and our risk of over 18 health conditions, symptoms and signs that we’re getting too EPA and DHA, the problems from supplementation with EPA and DHA, how much of these important fats we need, and shares the top 25 best common whole food sources of EPA and DHA. Paid subscribers also can download a printer-friendly PDF version of this information below!
The Biological Roles of EPA and DHA
All omega-3 fats are characterized by a shared feature in their chemical structure: a double bond located three atoms away from their terminal methyl group. They also contain multiple other double bonds, making them “polyunsaturated” fats (in contrast to monounsaturated fats, which have only one double bond, or saturated fats, which have none). In general, omega-3 fats are used for chemical reactions within cells that produce signaling molecules involved in inflammation, blood pressure regulation, and pain perception. They’re components of the cell membrane, where they alter important structural properties like membrane permeability, fluidity, and flexibility—consequently impacting the activity of membrane receptor systems and influencing gene expression and signaling pathways. The omega-3s we consume from food alter the proportion of omega-3 fats that end up in red blood cells, cardiac tissue, immune cells, atherosclerotic plaque, and more, in turn affecting the characteristics of these cells and the function of their receptors!
Omega-3 fats compete with omega-6 fats for the same conversion enzymes, as well as for positions in cell membranes—which is why we often hear about the importance
