If you've asked your doctor about what ratio of DHA to EPA you should be taking in your fish oil supplement, you may well have been greeted with a blank stare. The fact is that there is no official consensus, and no agreement as to which fatty acid should dominate the ratio. However, there is agreement on how much you should ingest of the precursor acids to ensure your body metabolizes a proper ratio.
Essential Fatty Acids
According to researchers reporting in the June 2006 issue of the "American Journal of Clinical Nutrition," scientists agree that the typical Western diet produces an imbalance in fatty acid intake which can contribute to health problems. There are two essential fatty acids, plant-sourced ones known as omega-6, and fish oil-derived fatty acids known as omega-3. EPA and DHA are omega-3s. Many Americans ingest so many omega-6s that they overwhelm our EPA and DHA, making supplementation necessary. Omega-6s are like kudzu that can overtake your lawn grass and choke it to death.
NIH Workshop
There are hundreds of published studies regarding fatty acid health benefits. The majority evaluate combinations of DHA and EPA. However few of the studies tested equivalent amounts of omega-3s so reviewers couldn't draw conclusions as to effective dosages. To settle the question, in 1999 the NIH assembled a group of experts and published their findings on its conference website. The experts decided on a quantity of 650 mg combined DHA and EPA in a ratio of two to one. It doesn't matter which acid predominates the mixture -- just that you consume twice as much of one as you do the other.
Chronic Disease Prevention
In 2002, the Institute of Medicine, or IOM, concluded there is insufficient data to define a Dietary Reference Intake, or DRI, for EPA and DHA; however it published an Acceptable Macronutrient Distribution Range, or AMDR. The IOM recommends your dietary intake of alpha-linolenic acid, or ALA, compose up to 1.2 percent of your total calorie intake to reduce the risk of chronic disease. ALA is the EPA and DHA precursor, and their reasoning behind not recommending a specific ratio is that your body will convert ALA into whichever acid it needs most. The full report is available online.
More From the IOM
To convert an appropriate ratio, your body's omega-6 intake must be within limits. The omega-6 precursor is linoleic acid and as referenced earlier, typical Western diets contain too much. Accordingly, the IOM set an adequate intake, or AI, for linoleic acid at 17 g per day for men and 12 g for women. That should represent no more than 10 percent of your total calorie intake. If women stay within this range while consuming 1.1 g ALA per day, and men consume about 1.6 g ALA daily, then in healthy people the conversion process will happen as nature intended.
References
- "American Journal of Clinical Nutrition"; Healthy Intakes of N--3 and N--6 Fatty Acids: Estimations Considering Worldwide Diversity; Joseph Hibbeln; June 2006
- "National Institutes of Health"; Workshop on the Essentiality of and Dietary Reference Intakes (DRIs) for Omega-6 and Omega-3 Fatty Acids; Artemis Simopoulos et al.; April 1999
- "Institute of Medicine"; Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids; National Academy Press; 2005
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