Arachidonic Acid: The Good and Bad
Arachidonic acid is an essential fatty acid, which is consumed in small amounts in our regular diets. It is considered an "essential" fatty acid because it is an absolute requirement for the proper functioning for the human body. Essential fatty acids (EFA's) are polyunsaturated fatty acids that the body cannot synthesize and therefore must obtain from the diet. There are two families of EFAs: omega-6 and omega-3. The most important omega-6 fatty acids are linoleic Acid (LA), gamma-linolenic acid (GLA), dihomogamma-linolenic acid (DGLA), and Arachidonic acid (AA). The most important omega-3 fatty acids are alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Omega-3 fatty acids can be found in fish and certain plant oils. Linoleic acid, an omega-6 fatty acid, can be found primarily in seeds, nuts, grains and legumes. Linoleic acid can be converted into arachidonic acid. Arachidonic acid can be found mainly in the fatty parts of meats and fish (largely red meat), so vegetarians usually have lower levels of arachidonic acid in the body than those with omnivorous diets.
There is a great deal of controversy about arachidonic acid. Some information says that arachidonic acid can cause health problems and other sources say it is needed to aid in muscle growth. Arachidonic acid is vital to the operation of the prostaglandin system. Prostaglandins are part of a class of substances called eicosanoids. Eicosanoids influence numerous metabolic activities including platelet aggregation (blood clotting), inflammation, hemorrhages, vasoconstriction and vasodilation, blood pressure, and immune function. The eicosanoids contain twenty carbons and include the prostaglandins (PG), prostacyclins (PGI2), thromboxanes (TX), leukotrienes (LT), and hydroxy acids. There are bad (pro-inflammatory) and good eicosanoids (anti-inflammatory) and they compete with each other. Two prostaglandins arachidonic acid is the substrate to are PGE2 and PGF2a. The first one is generally thought to be bad while the second is thought to be good. Studies point to PGF2a, specifically, as being the prostaglandin most closely tied to increase skeletal muscle protein synthesis. Skeletal muscle tissue has no capacity to actually store prostaglandins, so the only local source for PGF2a is the arachidonic acid that is retained in the outer phospholipids layer of each cell. It is the stretching of muscle fibers during intense physical exercise that causes arachidonic acid to be released and metabolized to active prostaglandins. Arachidonic acid is actually the chemical messenger first released by your muscles during intense weight training, controlling the core physiological response to exercise and regulating the intensity of all growth signals to follow. Also, anytime you have tissue injury, inflammation is involved in healing the wound. Some prostaglandins have pro-inflammatory affects. The fact is, if you work out, you have tissue injury - micro trauma to the muscle tissue. As your delayed onset muscle soreness will tell you, inflammation is involved in the healing of this micro trauma. Furthermore, in both animal and human studies it has been shown that exercise lowers the content of arachidnoic acid in skeletal muscle tissue. Therefore, there has been talk of arachidonic acid supplementation.
The omega-6 and omega-3 fatty acid families form different eicosanoids with different activities. They compete with one another for the enzyme (PLA2) that catalyzes the release of the essential fatty acids from the cell membrane. Also, they compete for cyclooxygenase and lipoxygenase, the enzymes necessary for eicosanoid synthesis. A proper balance of these fatty acids in the diet is therefore important for the maintenance of good health. An increase in the consumption of one family will reduce the synthesis of eicosanoids derived from the other family, which will ultimately have an effect on overall health. According to many sources, humans evolved on a 1:1 dietary ratio of omega-6 to omega-3. With today's typical "Western" dietary habits the average person consumes a dietary ratio of between 25 and 40 to 1 omega-6 to omega-3. This highly imbalanced ratio is due to the dramatic increase in consumption of omega-6 fatty acids in vegetable oils, which contain linoleic acid, and meat and shellfish, which contain arachidonic acid. At the same time, we are consuming less of the omega-3 fatty acids. Since the omega-6 compete with the omega-3 fatty acids for incorporation into cell membranes and subsequent metabolism, high intake of the omega-6 fatty acids will result in an increased production of unhealthy eicosanoids derived from arachidonic acid. Omega-3 fatty acids produce eicosanoids that are anti-inflammatory. These eicosanoids help support normal blood pressure by relaxing the arteries and blood vessels and decreasing blood lipids. They also decrease blood-clotting factors. Omega-6 fatty acids can produce both anti-inflammatory and/or inflammatory and vasoconstricting eicosanoids. Omega-6 can be good for you if you take them in the right amount with omega-3. Omega-3 can counteract the pro-inflammatory effects of omega-6 fatty acids. When omega-3 and omega-6 are in balance, they are both very good but when omega-6 is in excess, they become bad. For that reason, it is essential to have a proper balance of omega-6 and omega-3 fatty acids. A healthy ratio of omega-6 to omega-3 ranges from 1:1 to 1:3.
Now that arachidonic acid supplements are on the market, athletes need to be aware that there needs to be a balance of omega-6 and omega-3 fatty acids in their diet. Supplementation is acceptable only if you are consuming enough omega-3 fatty acids to balance with the added omega-6 fatty acid (arachidonic acid) from the supplement. You have a choice to make. If your primary concern is muscular gain supplementing arachidonic acid could help as long as you are consuming enough omega-3 to balance your diet. However, if you suffer from one of the many inflammatory conditions that plague many people who exercise (tendonitis, bursitis, arthritis, etc.) then you should probably stay away from it since it can be pro-inflammatory. Furthermore, if you suffer from diabetes, asthma, high blood pressure, high cholesterol, heart disease, are pregnant, or are suffering from any inflammatory disease you should not supplement arachidonic acid in your diet. Just remember if you are going to take arachidonic acid supplements you should have a healthy ratio of omega-6 to omega 3.
1. Galli, C., Simopoulos, A.P., Tremoli. Fatty Acids and Lipids: Biological Aspects. World Rev Nutr Diet 1994, 75: 1-196.
2. Mann and Sinclair. Contribution of Meat Fat to Dietary Arachidonic Acid. Lipids 1998, 33: 437-40
3. Phinney et al. Reduced Arachidonate in Serum Phospholipids and Cholesterol Esters Associated with Vegetarian Diets in Humans. Am. J. Clin. Nutr. 51: 385-92.
4. Rodemann, Peter and Alfred Goldberg. Arachidonic Acid, Prostaglandin E2 and F2a Influence Rates of Protein Turnover in Skeletal and Cardiac Muscle. J Biol Chem
5. Simopoulos, A.P., Leaf, A., Salem, N. Jr. Essentiality of and Recommended Dietary Intakes for Omega-6 and Omega-3 Fatty Acids. Ann Nutr Metab 1999, 43: 127-130.
6. Smith, WL. The Eicosanoids and Their Biochemical Mechanisms of Action. Biochem J 1989, 259:315-324.