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Fish oil (omega-3)

The classic omega-3 — best proven for lowering triglycerides, with a real (if debated) role in heart health.

Reviewed by Bodil Isaksson, Licensed Biomedical Scientist (Sweden)Last reviewed July 2026Supplement guide

SupplementsFatty acidsOmega-3Heart

Fish oil supplies the long-chain omega-3 fats EPA and DHA, the forms the body actually uses. It’s one of the most-studied supplements — with genuine effects, and some honest uncertainty.

Key takeaways

  • The active omega-3s are EPA and DHA — dose by their combined amount, not the fish-oil weight.
  • Fish oil reliably lowers triglycerides, dose-dependently.1
  • Cardiovascular benefit is real but modest and debated; high-dose EPA looks more protective than EPA+DHA blends.2
  • Choose products with a stated EPA+DHA content and low oxidation; oily fish 2×/week is the food-first route.

What it is

Fish oil is pressed from oily fish. Its value is the EPA and DHA content — a “1000 mg fish oil” capsule may contain only ~300 mg EPA+DHA, so read the label.

The evidence

Meta-analyses show omega-3 lowers triglycerides in a clear dose-response way.1 For cardiovascular events, results are mixed: overall benefit is modest, but high-dose purified EPA reduced events in high-risk patients, while some EPA+DHA trials were null.2 Omega-3 also supports brain and eye tissue (DHA is structural).

Dose

General health: ~250–500 mg EPA+DHA/day (or oily fish twice weekly). For raised triglycerides, 2–4 g/day EPA+DHA is used, usually under medical guidance.

Quality & safety

Pick a brand with a clear EPA+DHA figure and freshness/oxidation testing (rancid oil is common). High doses can thin the blood — caution before surgery or with anticoagulants. Purified oils are low in contaminants.

Bottom line: a well-evidenced omega-3 — excellent for triglycerides, useful (if debated) for the heart; buy on EPA+DHA content and freshness, not capsule size.

References

Adult research summary for education, not a prescription.

  1. Association between omega-3 fatty acid intake and dyslipidemia: a dose-response meta-analysis of RCTs. J Am Heart Assoc 2023. www.ahajournals.org
  2. Effect of omega-3 fatty acids on cardiovascular outcomes: a systematic review and meta-analysis. eClinicalMedicine 2021. pmc.ncbi.nlm.nih.gov

This article summarises nutrition science for education. It is not a substitute for individual medical advice; consult a professional before starting a supplement, in pregnancy, or alongside medication.