Exploring the sense and nonsense of food and health

EPA and DHA – Conflicting Evidence?


A typical fish oil softgel; not actual size

Image via Wikipedia

These highly omega-3 polyunsaturated fatty acids are the primary ingredients of fish oils and perform many important functions in the body.  DHA is the structural component of the brain and is found in high amounts in the retina of the eye.

EPA is the precursor of a number of biologically active compounds called eicosanoids involved in blood pressure regulation, blood clotting, and anti-inflammatory reactions.  Chronic inflammation is thought to be a central component in the chronic diseases of Western diets, namely, heart disease, diabetes type 2, osteoporosis, cancer, Alzheimer’s disease and rheumatoid arthritis.

Adequate intakes of EPA and DHA for adults are considered to be 650 mg per day.  You can get this amount by consuming 12 ounces of fish and shellfish weekly.  Consumption of two non-fried fishmeals a week reduces the risk of heart disease, heart attack, sudden death, and stroke and improves fetal and infant development.  Higher amounts of EPA and DHA (1-3 grams), generally provided by fish oils, can be used clinically to lower blood triglyceride levels, reduce the incidence of heart disease, and reduce the need for anti-inflammatory drug in people with rheumatoid arthritis.  Fish liver oils should be used with caution because they contain relatively high amounts of vitamins A and D.  Fish oils, made from the body of the fish, do not.

The ratio of omega-6 to omega-3 fatty acid intake is important because the functions of one are adversely affected by the presence of high amounts of the other. The ideal ratio (although still being studied) is 4:1, i.e. 4 omega-6 to 1 omega-3).  But since most Americans don’t eat a lot of fish and use a lot of vegetables oils, the ratio of omega-6:omega-3 fatty acids is about 9:1.

Research on omega-3 fatty acids suggests the following:

Against heart disease (supported by most studies:

v A shift toward omega-3 – eicosanoids by reducing production of omega-6 eicosanoids.

v Reduced blood triglycerides (In some studies, fish oil supplements elevated blood LDL cholesterol).

v Retarded hardening of the arteries

v Relaxation of blood vessels, mildly reducing blood pressure.

In infant growth and development (well researched and accepted)

v Normal brain development in infants.  DHA concentrates in the brain’s cortex, the conscious thinking part.

v Normal vision development in infants.  DHA helps to form the eye’s retina, the seat of normal vision


Again, as in previous posts, only take fish oil supplements with the supervision of your physician.  I found two studies that associated DHA with a higher risk of inflammatory bowel disease and colon cancer (a mouse study) as well as aggressive prostate cancer (a human study).

It seems contradictory since fish oil supplements are often recommended because they contain omega-3 fatty acids associated with a reduction in inflammation.

The authors noted that the results of the mouse study do not mean people should not take fish oil, but that healthful amounts need to be identified. “With fish oil, we don’t yet know how much is appropriate,” he said.

This study may serve as a warning to individuals with inflammatory bowel disease, which has an increased risk of developing colon cancer.

The bottom line is that if you adopt a healthy lifestyle and diet you will tip the scales in your favor against developing disease. If you do take fish oil supplements consider how much you are taking. There are other ways to reduce triglycerides, such as cutting back on refined sugars, so high doses should be avoided if possible.

Eat only good quality fish and cook it at a low heat. Avoid fish from polluted rivers and lakes.  Treat yourself to wild caught fish from clean areas.  Farmed fish contains coloring and pollutants.  Let’s wait and see what new research brings.  The best strategy for achieving a great omega-3/omega-6 ratio is reducing your intake of high-omega-6 foods like grains and industrial oils, rather than simply chugging back more omega-3 to compensate.

Mayo Clinic
Michigan State University
Purdue Research Foundation

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2 thoughts on “EPA and DHA – Conflicting Evidence?

  1. Eat oily fish:
    How much oily fish should you eat to not have to eat food supplements? To reach the daily requirement of omega 3 fish oil, you should ideally eat oily fish 2-3 times a week. Then, in the form of herring, salmon and anchovies. The daily dose of omega 3 oils are recommended to be at least 1 gram of pure omega 3. Gi Lunch
    Thanks for a great site.


  2. Pingback: 15 Ways To Hack Your Brain For A Better Life « Imagine the Spirit

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