Arachidonic acid, AA and sometimes ARA, is a 20 carbon long, omega-6, polyunsaturated fatty acid or n-6 PUFA. It is made in the body from shorter omega-6 fatty acids found in vegetable oils, or found in the diet in eggs, poultry and meats. PUFA are essential nutrients. Molecules made from AA are especially important in the growth and repair of muscle tissue and have effects on blood vessels, the heart, and nervous tissue. However, AA and other PUFA also play a role in the response to tissue damage and inflammation.
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Good or Bad Omega Fatty Acids
Whether a diet high in omega-6 vs omega 3 PUFA causes inflammation has been difficult to answer. The omega number indicates how for from the chain end the first unsaturated carbon lies. Omega 3 PUFA are found in cold water fish such as salmon or tuna and are relatively high in flaxseed and canola oils. Eicosapentaenoic acid -- or EPA -- and docosahexaenoic acid -- or DHA -- are omega 3 long chain PUFA. Cyclooxygenases -- COX enzymes - and other enzymes turn AA, EPA and DHA into molecules -- called eicosanoids -- that produce inflammation and cause platelets to clot but also relax blood vessels and stop inflammation.
Diet and Inflammatory Disease
Eicosanoids formed from AA regulate inflammatory responses as well as help tissue regenerate after the inflammation has subsided. These processes happen in cancer, asthma, rheumatoid arthritis and autoimmune disorders. Scientific studies on changing single components of a diet are difficult to do and often do not show clear cut results. However, where people have changed their diet -- to a Western diet -- that increased the omega 6 to omega 3 ratio, it has coincided with increases in chronic inflammatory diseases such as nonalcoholic fatty liver disease, cardiovascular disease, obesity, inflammatory bowel disease, rheumatoid arthritis, and Alzheimer's disease (See reference 1).
AA and Muscles
Because of the association with muscle tissue maintenance, AA supplements are being used by some body builders to enhance the training effects. A study in the "Journal of the International Society of Sports Nutrition" published in November 2007 found that after 25 days there was evidence of reduced inflammation in people who took AA supplements but no increase in strength or muscle growth.
Treatments for Inflammation
The discovery of the COX enzymes and the role of AA derived eicosanoids in pain and inflammation, led to the understanding that aspirin works by blocking COX enzymes. Medicines that are COX inhibitors -- called nonsterioidal anti-inflammatory drugs or NSAIDs such as ibuprofen, Celebrex -- celecoxib -- also block COX enzymes and relieve pain, inflammation and prevent heart attacks by blocking the actions of molecules derived from AA. However, NSAIDS may cause ulcers because they also block the formation of eicosanoids that help repair damages to the stomach and intestinal lining.
- Journal of Nutrition and Metabolsim: Health Implications of High Dietary Omega-6 Polyunsaturated Fatty Acids
- Inflammatory Bowel Diseases: Maintenance of Remission In Inflammatory Bowel Disease Using Omega-3 Fatty Acids (Fish Oil): A Systematic Review and Meta-analyses
- The British Journal of Nutrition: n-6 Fatty Acids and Cardiovascular Health: a Review of the Evidence For Dietary Intake Recommendations
- US Department of Agriculture and US Department of Health and Human Services. Dietary Guidelines for Americans. 2010
- Arteriosclerosis, Thrombosis, and Vascular Biology: Brief Review - Nutrition and Cardiovascular Disease
- The Journal of the International Society of Sports Nutrition: Effects Of Arachidonic Acid Supplementation On Training Adaptations In Resistance-Trained Males