Heneicosapentaenoic acid

Fatty-acidBest with a meal

What is it

Heneicosapentaenoic acid (HPA, 21:5 n-3) is a relatively rare omega-3 fatty acid with 21 carbons and 5 double bonds, found in some fish and algae oils. It is a minor component of marine omega-3 mixtures and is structurally between EPA (20:5) and DPA (22:5).

Evidence for 1 use

AI-assisted evidence assessment — talk to your doctor before relying on any single supplement.

Omega-3 status (as part of mixed marine omega-3s)

Mixed Evidence

Insufficient evidence specific to HPA. Effects are likely similar to other long-chain omega-3 fatty acids, which have substantial evidence for cardiovascular and inflammatory outcomes when consumed as EPA/DHA.

How it works

Like other long-chain omega-3 fatty acids, HPA is incorporated into cell membrane phospholipids and can be metabolized to specialized pro-resolving mediators (resolvins, protectins) that help end inflammatory responses. Because HPA occurs in such small amounts in food and supplements, it has not been studied extensively in isolation. Its biological behavior is presumed to be similar to EPA, but specific data are limited.

Dosage

No standardized dose. HPA usually appears as a minor component (typically <1%) of fish oil or algae oil products, not as a standalone supplement.

When and how to take it

Take with a meal containing fat for absorption. HPA is naturally consumed as part of mixed omega-3 supplements.

1 commercial form

Compare the main delivery options and what they’re best suited for.

Trace component of fish oil / algae oil

Not typically sold as an isolated supplement.

Absorbed with fat; similar to EPA/DHA.

Safety

Limited specific safety data. Inferred from general omega-3 safety - generally well tolerated at typical fish oil doses. Side effects may include mild gastrointestinal upset and a fishy aftertaste.

Who should be cautious

Specific cautions follow those of fish/algae oils generally - check with a clinician if on anticoagulants. People with fish or shellfish allergy should be careful with marine-derived sources.

Interactions

Like other long-chain omega-3s, may have mild antiplatelet activity at high doses, potentially adding to anticoagulant medications.

Food sources

Fatty fish (salmon, mackerel, sardines)

Amount
3 oz (85 g)
%DV
—

Frequently asked questions

Is HPA different from EPA?⌄

Yes. HPA (heneicosapentaenoic acid) has 21 carbons; EPA (eicosapentaenoic acid) has 20. They are structural relatives but distinct molecules.

Should I look for HPA specifically?⌄

There is no compelling reason to seek out HPA over standard EPA/DHA fish oil or algae oil. HPA is a minor component without specific clinical evidence.

References

Heneicosapentaenoic acid on Wikidata — Wikidata link

Heneicosapentaenoic acid (ChEBI:165480) — ChEBI link

Heneicosapentaenoic acid (PubChem CID 11998573) — PubChem link

Heneicosapentaenoic acid on NIH DSLD (US supplement label database) — NIH Dietary Supplement Label Database link

Research on Heneicosapentaenoic acid (PubMed search) — PubMed link

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Evidence-based·How we grade evidence

Disclaimer: These statements have not been evaluated by the FDA. This page is educational, not a substitute for personalized medical advice. Evidence grades are AI-assisted assessments — talk to your doctor before starting any new supplement, especially if you’re pregnant, breastfeeding, on medications, or managing a chronic condition.