Omega-3 Fatty Acid

Aka: Omega-3 Fatty Acid, Omega-3 Polyunsaturated Fatty Acid, Eicosapentaenoic Acid, Docosahexaenoic Acid, Alpha linolenic Acid

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II. Indications

  1. Coronary Heart Disease Prevention (1 gram/day)
    1. Degree of cardiovascular benefit is unclear (see efficacy below)
    2. No longer recommended for Coronary Artery Disease secondary prevention, unless Hypertriglyceridemia
      1. Do not appear to lower risk of cardiovascular events
    3. References
      1. Tadic (2021) J Clin Med 10(11):2495 +PMID: 34200081 [PubMed]
      2. Siscovick (2017) Circulation 135:e867-84 +PMID: 28289069 [PubMed]
  2. Other indications under study (2-4 grams/day)
    1. Hypertriglyceridemia
    2. Hypertension
    3. Rheumatoid Arthritis

III. Physiology

  1. Essential Fatty Acids
  2. Properties
    1. Anti-inflammatory
    2. Antithrombotic
    3. Antiarrhythmic
    4. Vasodilatory
  3. Benefits
    1. Possible effects at 1 gram/day of omega-3 (unclear efficacy data - see below)
      1. May reduce risk of sudden death
      2. May reduce all-cause mortality
    2. Other effects at 2-4 grams/day of omega-3
      1. Precaution: These doses require further study
      2. Lowers Serum Triglycerides
        1. High doses of omega-3 may raise LDL Cholesterol
      3. Reduces symptoms in Rheumatoid Arthritis
      4. Lowers Blood Pressure in Hypertension

IV. Types: Polyunsaturated Fatty Acids (PUFA)

  1. Acids from fish and fish oils
    1. Eicosapentaenoic Acid (EPA)
      1. Does not raise LDL Cholesterol significantly
      2. Triglycerides lowered more effectively when EPA used in combination with DHA
    2. Docosahexaenoic Acid (DHA)
      1. Increases LDL Cholesterol
      2. Significantly boosts Triglyceride lowering effect of EPA
  2. Acids from seed, green leafy vegetables, nuts and beans
    1. Alpha linolenic Acid (ALA)

V. Sources: Plant (mostly Alpha linolenic Acid, about a third the potency of EPA/DHA)

  1. Nuts
    1. Almonds
    2. Dried butternut
    3. English walnuts
  2. Miscellaneous
    1. Flaxseed
    2. Raw Soybeans
    3. Pinto beans
    4. Wheat germ
    5. Purslane
    6. Leeks
  3. Oils
    1. Canola oil
    2. Fish oil
    3. Flaxseed oil
    4. Walnut oil
    5. Soybean oil
      1. Also contains Omega-6 Fatty Acids (prothrombotic)

VI. Sources: Fish (EPA or DHA per 3 ounces of fish)

  1. General
    1. Omega 3 Fatty Acid content varies considerably
      1. Depends on species, season, diet, and processing
  2. Fish with high omega 3 levels (>1 grams/3 ounces)
    1. Albacore tuna
      1. Fresh: Up to 1.3 grams
      2. Canned white in water: Up to 0.75 grams
    2. Herring, sardines or anchovy: Up to 1.7 grams
    3. Halibut: Up to 1 gram
    4. Mackerel: Up to 1.5 grams
    5. Salmon
      1. Atlantic, Chinook: Up to 1.5 grams
      2. Sockeye: Up to 0.7 grams
  3. Fish and seafood with lower omega 3 levels (<0.4 grams)
    1. Catfish
    2. Alaskan king crab
    3. Flounder or sole
    4. Haddock
    5. Shrimp

VII. Sources: Supplement

  1. See Fish Oil Supplement

VIII. Precautions

  1. See Mercury Content in Fish
  2. Prostate Cancer increased risk in some studies (preliminary)
    1. Brasky (2013) J Natl Cancer Inst 105:1132 [PubMed]
    2. Brasky (2011) Am J Epidemiol 173(12): 1429–39 [PubMed]

IX. Efficacy: Conditions for which Omega-3 Fatty Acids have no consistently proven benefit

  1. Cardiovascular disease primary prevention (variable evidence, but no consistent proven benefit)
    1. Manson (2019) N Engl J Med 380(1): 23-32 [PubMed]
    2. Study of 11,000 post-Myocardial Infarction patients on 850 mg Omega-3 Fatty Acids per day
      1. Had a 45% reduction in cardiac death and 20% mortality reduction overall
      2. Burr (1989) Lancet 2:757-61 [PubMed]
    3. Italian Study of 12,000 patients with multiple Cardiovascular Risk Factors
      1. Showed no reduction in cardiovascular morbidity or mortality over 5 years
      2. (2013) Engl J Med 368(19):1800-8 +PMID:23656645 [PubMed]
    4. Additional studies of Omega-3-Fatty Acids not significantly lowering Cardiovascular Risk
      1. (2021) Presc Lett 28(1): 1-2
      2. Nicholls (2020) JAMA 324(22):2268-80 [PubMed]
  2. Cancer primary prevention (no proven benefit)
    1. Manson (2019) N Engl J Med 380(1): 23-32 [PubMed]

X. References

  1. Covington (2004) Am Fam Physician 70(1):133-40 [PubMed]
  2. Harper (2001) Arch Intern Med 161:2185-92 [PubMed]
  3. Holub (2002) CMAJ 166(5):608-15 [PubMed]
  4. O'Keefe (2000) Mayo Clin Proc 75:607-14 [PubMed]

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