Omega-3s: EPA vs. DHA vs. ALA & the Conversion Problem

Omega-3 fatty acids are among the most researched nutrients, but the differences between the three main forms — ALA (from plants), EPA (from marine sources), and DHA (from marine sources) — are significant and often overlooked. Saying you "take omega-3s" without specifying the form tells an incomplete story.

The Conversion Problem

ALA (alpha-linolenic acid) from flaxseed, chia seeds, and walnuts is the plant-based omega-3. The body can convert ALA to EPA and DHA, but conversion efficiency is extremely low: roughly 5-10% to EPA and less than 1% to DHA. This means plant-based ALA is not a reliable substitute for marine EPA/DHA for individuals who need the specific benefits of these long-chain forms.

EPA vs. DHA

EPA (eicosapentaenoic acid) is more associated with anti-inflammatory effects, mood regulation, and cardiovascular benefits. DHA (docosahexaenoic acid) dominates neural tissue and is critical for brain structure and function. Most research suggests both are important, but the optimal ratio may differ by health goal.

Food Sources

Fatty fish (salmon, mackerel, sardines, herring, anchovies) are the best EPA/DHA sources. Algal oil supplements provide DHA (and some EPA) from a vegan source — the algae are actually where fish get their omega-3s in the first place.

See also Omega-6 Balance for the ratio debate.

External resources: NIH — Omega-3 Fact Sheet