This information describes the common uses of Omega-3, how it works, and its possible side effects.

Common Name

O3FAs, ω-3 fatty acids, n-3 fatty acids

How It Works

Omega-3 fatty acids have not been shown to prevent cancer.

Omega-3 fatty acids are obtained from fish oil. They have been used to protect against cardiovascular events such as heart attack. Studies have shown that omega-3 fatty acids can be taken up by the fatty deposits that line the arteries, thereby improving the stability of those deposits. Omega-3 fatty acids do not seem to affect the clotting of blood. Omega-3 fatty acids may reduce inflammation by decreasing some of the signals that cells send to each other. It is thought that patients with colitis, asthma, cystic fibrosis and those before surgery may benefit from this reduced inflammatory effect. Omega-3 fatty acid supplements have been shown to be absorbed by the skin and protect it against ultra-violet radiation damage.

Omega-3 fatty acids may reduce the risk of breast cancer, but may increase the risk of prostate cancer.

Purported Uses

  • To treat asthma
    A review of published trials shows no effect of omega-3 on asthma.
  • To treat fatty deposits on the inside of arteries (atherosclerosis)
    Studies have shown that omega-3 can increase the stability of these deposits, which may make them less dangerous.
  • To protect against cardiovascular disease
    Studies have shown that omega-3 can reduce the frequency and severity of cardiovascular events such as heart attacks.
  • To improve the symptoms of colitis
    Studies have shown that omega-3 may improve the symptoms associated with colitis.
  • To alleviate the symptoms associated with cystic fibrosis
    One study showed an improvement in breathing parameters for patients taking omega-3 supplements, however other trials have shown no benefit. Larger studies are necessary to determine the actual effect.
  • To treat symptoms of lupus
    A small study found a reduction in symptoms of lupus in patients who took fish oil compared with those on placebo. More trials are needed to support this claim.
  • To alleviate depression
    A study of a few thousand people in Finland found that people who ate less fish were more likely to have the symptoms of depression than those who ate more fish. Other studies have also shown a connection between omega-3 levels and depression scores, however few studies have attempted to determine if omega-3 supplementation affects depression symptoms.
  • To lower cholesterol levels
    A review of published trials of omega-3 for lowering cholesterol levels in patients with diabetes found that while omega-3 lowered triglyceride levels, it also raised LDL cholesterol levels.
  • To treat psychiatric disorders
    A recent study showed that omega-3 may be useful in reducing the risk of progression to psychiatric disorders.
  • To protect the skin against ultra-violet radiation damage.
    Studies have shown omega-3 to be incorporated into the skin and offer protection against UV damage which may reduce cancer risk.
  • To prevent cancer
    Omega-3 fatty acids may reduce the risk of breast cancer, but may increase the risk of prostate cancer.

Do Not Take If

  • You are taking Warfarin: Elevated INR has been reported when taken with fish oil supplements (2 g/day). INR decreased after reducing supplement intake.
    High dose omega-3 supplements have been associated with subdural hematoma [6g/day] requiring craniotomy; and irreversible warfarin-induced coagulopathy following blunt head trauma.
  • You are taking glucocorticoids: Omega-3 supplements worsened some side effects caused by glucocorticoids in a mice model. Clinical significance is not known.

Side Effects

  • Fishy aftertaste, loose stools and nausea have been reported following intake of large doses of omega-3 fatty acids.
  • Gastrointestinal events (diarrhea, nausea, and abdominal pain), and atrial fibrillation have been reported with EPA intake in a clinical study.

Special Point

Omega-3 fatty acids should not be confused with omega-6 fatty acids, such as those found in evening primrose oil and borage oil, which have different effects in the body.