Omega-3 fatty acids are not all created equal. Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) are found primarily in fish and so are called "marine" omega-3s. Alpba-linolenic acid (ALA) is found in plant sources such as flaxseed, walnuts, canola oil, soybean oil.

Evidence for health benefits is much stronger for EPA and DHA than for ALA. The marine omega-3s appear to protect against…

  • Heart attacks, stroke and cardiovascular death—by reducing blood clotting, irregular heart rhythms, triglycerides (a blood fat) and perhaps arterial plaque.
  • Cognitive decline and depression—by combating inflammation, improving function of nerve cell membranes and boosting brain chemicals that help nerve cells communicate.
  • Some types of arthritis and bowel disease—by easing inflammation.

Bonus: Omega-3s may reduce menstrual cramps and menopausal hot flashes in some women.

How much do you need? Adults should eat dark oily fish (such as salmon, tuna, herring, sardines, trout or mackerel) at least twice per week. This provides 400 milligrams (mg) to 500 mg of combined EPA/DHA per day, on average.

If you have heart disease, get 1,000 mg of EPA/DHA daily...if you have high triglycerides, your doctor may recommend 2,000 mg to 4,000 mg daily.

It's hard to eat enough fish to meet the higher dosages, so consider supplements.

Advantage: Whereas fish may be contaminated with mercury and polychlorinated biphenyls (PCBs). Consumer Reports found that none of the 16 major fish oil brands tested contained significant amounts of these toxins.

Bonus: Fish oil may alleviate dry eyes and dry skin. Keep in mind...

  • Many fish oil capsules are only about 30% EPA/DHA-so look for a product with more concentrated EPA/DHA.

If you have high triglycerides, ask your doctor for information about a new prescription fish oil supplement that has 840 mg of EPA/DHA per 1,000-mg capsule

  • Fish oil can thin the blood and trigger excessive bleeding in some people-so do not take more than 3,000 mg daily without your doctor's okay. Check with your doctor before taking any fish oil if you use medication that affects blood clotting, such as aspirin, warfarin (Coumadin) or clopidogrel (Plavix).

If you prefer not to consume fish products, get 1,000 mg to 2,000 mg of ALA per day from ground flaxseed, flaxseed oil supplements or other sources

To avoid gastrointestinal upset, start at a low dose and gradually build up.. and drink a glass of water with each dose.

Consult your doctor before taking high doses of flaxseed if you have a personal or family history of breast cancer or another hormone-sensitive condition-flaxseed contains substances that may have estrogen-like effects.

  • New study under way. My colleagues and I have begun the first-ever large-scale clinical trial designed to provide a definitive picture of the benefits and risks of marine omega-3 supplementation for initially healthy men and women.

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