OMEGA-3 SCIENCE FIELD GUIDE

EPA vs DHA vs ALA: what is the difference?

Omega-3 is a family of fatty acids. ALA, EPA and DHA are related, but they are not interchangeable study interventions.

ALA: 18 carbons and 3 double bonds; EPA: 20 carbons and 5 double bonds; DHA: 22 carbons and 6 double bonds — ALA (18:3 n−3), EPA (20:5 n−3) and DHA (22:6 n−3). The ribbons are conceptual illustrations, not molecular models. View full size ↗

The short answer

ALA is an essential fatty acid found in plant foods such as flaxseed, chia seeds and walnuts. EPA and DHA are long-chain omega-3s found in fish and seafood; algal oils can supply DHA and, depending on the preparation, EPA. The body can convert ALA to longer-chain forms, but conversion is limited. Source: NIH Office of Dietary Supplements.

Is EPA or DHA better?

There is no universal winner. DHA is an important structural component of cell membranes, particularly in the brain and retina. EPA and DHA also participate in pathways involved in cell signaling. A biological role does not establish that taking more prevents or treats a particular disease.

Why the formulation matters in clinical trials

Evidence for a prescription EPA preparation in a selected cardiovascular population cannot simply be transferred to an over-the-counter fish oil or an algal oil. The dose, comparator, participants and outcomes need to match the question being asked.

Compare the actual doses and formulations in seven study examples →

Does fish oil weight equal EPA plus DHA?

No. The total oil weight may include other fats. Read the separate EPA and DHA amounts per serving, then check how many capsules make a serving. ALA amounts should not be added as if they were equivalent EPA or DHA.

What should I explore next?

Educational synthesis based on the NIH omega-3 fact sheet. Independent clinical review pending.

Editorial attribution: PV Griscom, M.Sc. · Independent clinical review pending.