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Nutrition
Nutrition

Omega-3 and Omega-6 Essential Fatty Acids

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omega-3omega-6epadhaalaessential-fatty-acidsfish-oil

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Explainer
In one line

Omega-3 and omega-6 are polyunsaturated fats the body cannot make; most people get plenty of omega-6 but too little long-chain omega-3 (EPA/DHA) from fish.

Detail

Essential fatty acids must come from food. There are two families:

  • Omega-3: the plant form ALA (alpha-linolenic acid; flaxseed, chia, walnuts) and the long-chain marine forms EPA and DHA (fatty fish — salmon, sardines, mackerel). EPA/DHA support cardiovascular health, are structural in the brain and retina, and modulate inflammation. The body converts ALA to EPA/DHA only inefficiently (a few percent).
  • Omega-6: chiefly linoleic acid (vegetable oils, nuts, seeds), abundant in typical Western diets.

Intake guidance:

  • Dietary Reference Intakes: there is no RDA for any omega-3 or for EPA/DHA. The DRIs set an Adequate Intake for ALA of 1.6 g/day (men) and 1.1 g/day (women), and an acceptable range for omega-3s of 0.6–1.2% of calories, of which up to about 10% can come from long-chain EPA/DHA. For omega-6 (linoleic acid) the AI is 17 g/day (men) and 12 g/day (women) aged 19–50, within a range of 5–10% of calories.
  • American Heart Association: its 2018 science advisory suggests 1–2 seafood meals per week to lower the risk of heart failure, coronary heart disease, ischemic stroke and sudden cardiac death, especially when seafood replaces less healthy foods. Its 2026 dietary guidance says to eat fish and seafood regularly, and adds that fish-oil supplements alone have not been shown to lower cardiovascular risk in otherwise healthy adults and may be linked to higher atrial-fibrillation risk in some people.
  • Existing heart disease: in 2002 the AHA recommended ≈1 g/day EPA + DHA for people with documented coronary heart disease, preferably from oily fish; its 2017 advisory still judged supplementation reasonable for secondary prevention after a recent coronary event, in consultation with a physician. Prescription doses of 4 g/day are a separate, medically supervised treatment for high triglycerides (AHA 2019 advisory).
  • FDA safety limits: 3 g/day is FDA's cap on EPA + DHA from conventional foods (menhaden-oil GRAS rule); for supplements, FDA concluded in 2019 that products providing no more than 5 g/day EPA + DHA are safe when used as labelled, with too little evidence above that.

Vegans and vegetarians rely on ALA plus algae-derived EPA/DHA and are a key at-risk group for low long-chain omega-3 status (see Plant-Based, Vegetarian, and Vegan Diets).

Key facts

  • Two essential families: omega-3 (ALA; EPA/DHA) and omega-6 (linoleic acid).
  • EPA/DHA from fatty fish; ALA→EPA/DHA conversion is inefficient.
  • No RDA; DRI Adequate Intake for ALA 1.6 g/day (men), 1.1 g/day (women); omega-3 range 0.6–1.2% of calories.
  • AHA: 1–2 seafood meals/week (2018); fish oil alone hasn't been shown to cut CVD risk in healthy adults (2026).
  • Coronary heart disease: ≈1 g/day EPA+DHA (AHA 2002), supplementation reasonable after a recent event (AHA 2017), with a physician.
  • FDA: ≤3 g/day EPA+DHA from conventional foods; supplements ≤5 g/day judged safe (2019).
  • Vegans/vegetarians at risk; algae oil is a vegan EPA/DHA source.

Connections

Sources

  1. GuidelineInstitute of Medicine. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids. Washington, DC: The National Academies Press Published 2005 · DOI 10.17226/10490 · Accessed 2026-10-13
  2. GuidelineNational Academies of Sciences, Engineering, and Medicine. Dietary Reference Intakes for Sodium and Potassium, Appendix J: Dietary Reference Intakes Summary Tables (macronutrient AIs and AMDRs) Published 2019 · DOI 10.17226/25353 · Accessed 2026-10-13
  3. GuidelineRimm EB et al. Seafood Long-Chain n-3 Polyunsaturated Fatty Acids and Cardiovascular Disease: A Science Advisory From the American Heart Association. Circulation 2018;138(1) Published 2018 · DOI 10.1161/CIR.0000000000000574 · Accessed 2026-10-13
  4. GuidelineSiscovick DS et al. Omega-3 Polyunsaturated Fatty Acid (Fish Oil) Supplementation and the Prevention of Clinical Cardiovascular Disease: A Science Advisory From the American Heart Association. Circulation 2017;135(15) Published 2017 · DOI 10.1161/CIR.0000000000000482 · Accessed 2026-10-13
  5. GuidelineSkulas-Ray AC et al. Omega-3 Fatty Acids for the Management of Hypertriglyceridemia: A Science Advisory From the American Heart Association. Circulation 2019;140(12) Published 2019 · DOI 10.1161/CIR.0000000000000709 · Accessed 2026-10-13
  6. GuidelineLichtenstein AH et al. 2026 Dietary Guidance to Improve Cardiovascular Health: A Scientific Statement From the American Heart Association. Circulation 2026;153 Published 2026 · DOI 10.1161/CIR.0000000000001435 · Accessed 2026-10-13
  7. SourceUS FDA. Letter of enforcement discretion to GOED: Petition for a Health Claim for EPA and DHA and Reduction of Blood Pressure in the General Population (Docket FDA-2014-Q-1146) Published 2019 · Accessed 2026-10-13
Also cited in text
Institute of Medicine, DRIs for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2002/2005; doi:10.17226/10490), via the NASEM DRI summary tables (2019, doi:10.17226/25353). Rimm EB et al., AHA science advisory, Circulation 2018 (doi:10.1161/CIR.0000000000000574). Siscovick DS et al., AHA science advisory, Circulation 2017 (doi:10.1161/CIR.0000000000000482). Skulas-Ray AC et al., AHA science advisory, Circulation 2019 (doi:10.1161/CIR.0000000000000709). Lichtenstein AH et al., 2026 AHA dietary guidance, Circulation 2026 (doi:10.1161/CIR.0000000000001435). US FDA letter of enforcement discretion to GOED, June 2019 (fda.gov/media/128043).
Corrections (1)
  • 2026-10-13 — Intake guidance rewritten against primary documents. DRI: there is no RDA for any omega-3; the 2005 macronutrient DRIs set an Adequate Intake for ALA only (1.6 g/day men, 1.1 g/day women) and an n-3 AMDR of 0.6–1.2% of energy, up to ~10% of which can come from EPA/DHA. AHA: the 2018 advisory suggests 1–2 seafood meals per week; the '~1 g/day EPA+DHA for heart disease' figure is the AHA's 2002 recommendation, which the 2017 advisory kept in substance (supplementation 'reasonable' for secondary prevention after a recent CHD event, with a physician); the 2026 AHA statement adds that fish oil alone has not been shown to lower CVD risk in otherwise healthy adults and may raise atrial-fibrillation risk in some. FDA: corrected '3 g/day GRAS as a supplement ceiling' — 3 g/day is FDA's limit for EPA+DHA from conventional foods (menhaden-oil GRAS rule, 1997/2005); for supplements FDA's 2019 letter concluded ≤5 g/day EPA+DHA is safe and lawful as labelled. Removed the unattributed '250–500 mg/day from health organizations' figure (no current primary document checked); NIH ODS citation removed (not retrievable 2026-10-13).

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