What are omega-3 and omega-6 fatty acids?

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What are omega-3 and omega-6 fatty acids?

September 15, 2010

Salmon - A Good Source of Omega-3 and Omega-6 AcidsThe health benefits of omega-3s have caught fire among consumers.  Savvy food manufacturers and marketers have taken note and managed to add the fatty acids to a wide variety of foods.  Subway recently launched omega-3-enriched whole grain bread; you can easily buy omega-3 enriched milk and dairy products; multiple cereals promote their high omega-3 content; and even some pet food is fortified with the stuff.  The reason for the craze may be due to a growing body of research and media attention suggesting that omega-3 fatty acids offer numerous health benefits including decreased risk of heart disease, improved brain development in fetuses and young children, and reduced disability form mental illnesses such as depression and attention deficit and hyperactivity disorder (ADHD).  But not all omega-3s are equally beneficial.  And despite theoretical concerns that the other essential polyunsaturated fatty acids – omega 6 fatty acids – might be bad for you, the latest indication is that these fats also help to improve your overall health.

Omega 3 and omega 6 fatty acids are both essential polyunsaturated fats.  Polyunsaturated fats by definition contain a double bond between two or more sets of carbons in their chemical structure, are typically liquid at room temperature, and are fairly unstable making them susceptible to oxidative damage and a shortened shelf life.  Essential fatty acids are not produced by the body, and therefore, must be obtained from the diet. 

Understanding omega-3

Omega-3 fatty acids come in three forms: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexanoic acid (DHA).   ALA is the type of omega-3 found in plants.  It can be converted to EPA and DHA in the body, but so far, the research supporting the benefits of ALA is much less compelling than that for EPA and especially DHA.   DHA and EPA omega-3 fatty acids are naturally found in egg yolk and cold water fish like tuna, salmon, mackerel, cod, crab, shrimp and oyster.  Overall, omega-3s reduce blood clotting, dilate blood vessels, and reduce inflammation.  They are important for eye and brain development (especially important for a growing fetus in the late stages of pregnancy); act to reduce cholesterol and triglyceride levels; and may help to preserve brain function and reduce risk of mental illness and ADHD, though more research is needed to confirm these mental health benefits.  Notably, most Americans tend not to get enough of omega-3 fatty acids.  Though natural food sources are best, people who do not meet this recommendation may benefit from supplementation or from fortified foods.  While there is no established Dietary Reference Intake (DRI) for the optimal amount of EPA+DHA intake, some expert panels have recommended an intake between 250-500mg per day.  This dosage is likely safe and effective to achieve the benefits of the omega-3s without increased risk of complications such as bleeding.  Of note, while many products claim to be fortified with omega-3s, it is important for consumers to read the label.  If the omega-3s are mostly ALA (as is the case with the omega-3-fortified bread at Subway) they are unlikely to be optimally converted to EPA and DHA and likely have fewer of the health benefits. If the added omega-3s are of a negligible amount, it’s also unlikely that the added cost of the product is worth the limited benefit.

Understanding omega-6

Omega-6, generally consumed in abundance, is an essential fatty acid found in flax seed, canola, and soybean oils and green leaves.  It works opposite to omega-3s in that it seems to contribute to inflammation and blood clotting.  The balancing act between omega-6 and omega-3 is essential for maintaining normal circulation and other biological processes.  In the past, scientists have hypothesized that reducing consumption of omega-6 fatty acids and increasing consumption of omega-3 fatty acids may lower chronic disease risk, but more recent research has shown that maintaining a high consumption of both omega-3 and omega-6 fatty acids has cardiovascular health benefits.  The American Heart Association recommends that Americans consume 5-10% of calories of omega-6 polyunsaturated fatty acids – that’s about 12 grams per day for women and 17g for men.

Optimizing your omega intake

So what should you do to optimize your omega-3 and omega-6 intake?  Here are a few simple tips:

  • Aim to consume at least 3oz of DHA-rich fish such as tuna, salmon, mackerel, cod, crab, shrimp and oysters two times per week.
  • When choosing a food fortified with omega-3s, preferentially choose those that contain DHA.
  • If you’re pregnant or nursing or at risk of heart disease, discuss with your doctor whether you should be taking a DHA supplement.
  • Continue to consume a diet with adequate amounts of omega-6 fatty acids.  Foods rich in omega-6 include nuts, liquid vegetable oils, and margarines made with vegetable oils.  It’s not too difficult to consume recommended amount of 12-17g per day-- a tablespoon of corn or soybean oil provides about 7g of linoleic acid.

 

References:

Harris WS, Mozaffarian D, Rimm E, et al (2009).  Omega-6 fatty acids and risk for cardiovascular disease.  A science advisory from the American Heart Association Nutrition Subcommittee of the Council on Nutrition, Physical Activity, and Metabolism; Council on Cardiovascular Nursing; and Council on Epidemiology and Prevention. Circulation, 119, 902-907.

Riediger ND, Othman RA., Suh M, et al (2009).  A systematic review of the roles of n-3 fatty acids in health and disease.  Journal of the American Dietetic Association, 109, 668-679.

Kris-Etherton PM, Grieger JA, Etherton TD (2009).  Dietary reference intakes for DHA and EPA.  Prostaglandins Leuko Essent Fatty Acids, 81, 2-3, 99-104.

 

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