What are the real differences between EPA and DHA?

The first casualty of marketing is usually the truth. The reality is that the two key omega-3 fatty acids (EPA and DHA) do a lot of different things, and as a result the benefits of EPA and DHA are often very different. That’s why you need them both. But as to why, let me go into more detail.

Benefits of EPA

The ultimate goal of using omega-3 fatty acids is the reduction of cellular inflammation. Since eicosanoids derived from arachidonic acid (AA), an omega-6 fatty acid, are the primary mediators of cellular inflammation, EPA is the most important of the omega-3 fatty acids to reduce cellular inflammation for a number of reasons. First, EPA is an inhibitor of the enzyme delta-5-desaturase (D5D) that produces AA (1). The more EPA you have in the diet, the less AA you produce. This essentially chokes off the supply of AA necessary for the production of pro-inflammatory eicosanoids (prostaglandins, thromboxanes, leukotrienes, etc.)

DHA is not an inhibitor of this enzyme because it can’t fit into the active catalytic site of the enzyme due to its larger spatial size. As an additional insurance policy, EPA also competes with AA for the enzyme phospholipase A2 necessary to release AA from the membrane phospholipids (where it is stored). Inhibition of this enzyme is the mechanism of action used by corticosteroids. If you have adequate levels of EPA to compete with AA (i.e. a low AA/EPA ratio), you can realize many of the benefits of corticosteroids but without their side effects. That’s because if you don’t release AA from the cell membrane, you can’t make inflammatory eicosanoids. Because of its increased spatial dimensions, DHA is not a good competitor of phospholipase A2 relative to EPA. On the other hand, EPA and AA are very similar spatially so they are in constant competition for the phospholipase A2 enzyme, just as both fatty acids are in constant competition for the delta-5 desaturase enzyme. This is why measuring the AA/EPA ratio is such a powerful predictor of the state of cellular inflammation in your body.

The various enzymes (COX and LOX) that make inflammatory eicosanoids can accommodate both AA and EPA, but again due to the greater spatial size of DHA, these enzymes will have difficulty-converting DHA into eicosanoids. This makes DHA a poor substrate for these key inflammatory enzymes. Thus DHA again has little effect on cellular inflammation, whereas EPA can have a powerful impact.

Finally, it is often assumed since there are not high levels of EPA in the brain, that it is not important for neurological function. Actually, it is key for reducing neuro-inflammation by competing against AA for access to the same enzymes needed to produce inflammatory eicosanoids. However, once EPA enters into the brain, it is rapidly oxidized (2,3). This is not the case with DHA (4). The only way to control cellular inflammation in the brain is to maintain high levels of EPA in the blood. This is why all the work on depression, ADHD, brain trauma, etc., has demonstrated that EPA is superior to DHA (5).

Benefits of DHA

At this point, you might think that DHA is useless. Just the opposite, because DHA can do a lot of different things than EPA and some of them even better.

First is in the area of omega-6 fatty acid metabolism. Whereas EPA is the inhibitor of the enzyme (D5D) that directly produces AA, DHA is an inhibitor of another key enzyme, delta-6-desaturase (D6D), that produces the first metabolite from linoleic acid known as gamma linolenic acid or GLA (6). However, this is not exactly an advantage. Even though reduction of GLA will eventually decrease AA production, it also has the more immediate effect of reducing the production of the next metabolite known as dihomo gamma linolenic acid or DGLA. This can be a disaster as a great number of powerful anti-inflammatory eicosanoids are derived from DGLA. This is why if you use high-dose DHA, it is essential to add back trace amounts of GLA to maintain sufficient levels of DGLA to continue to make anti-inflammatory eicosanoids.

In my opinion, the key benefit of DHA lies in its unique spatial characteristics. As mentioned earlier, the extra double bonds and length of DHA compared to EPA means it takes up a lot more space in the membrane. Although this increase in spatial volume makes DHA a poor substrate for phospholipase A2 as well as the COX and LOX enzymes, it does a great job of making membranes (especially those in the brain) a lot more fluid as the DHA sweeps out a much greater volume in the membrane than EPA. This increase in membrane fluidity is critical for synaptic vesicles and the retina of the eye because it allows receptors to rotate more effectively, thus increasing the transmission of signals from the surface of the membrane to the interior of the nerve cells. This is why DHA is a critical component of these parts of the nerves (7). On the other hand, the myelin membrane is essentially an insulator so that relatively little DHA is found in that part of the membrane.

This constant sweeping motion of DHA also causes the breakup of lipid rafts in membranes (8). Disruption of these islands of relatively solid lipids makes it more difficult for cancer cells to continue to survive and more difficult for inflammatory cytokines to initiate the signaling responses to turn on inflammatory genes (9). In addition, these greater spatial characteristics of DHA increase the size of LDL particles to a greater extent compared to EPA. As a result DHA helps reduce the entry of these enlarged LDL particles into the muscle cells that line the artery, thus reducing the likelihood of developing atherosclerotic lesions (10). Thus the increased spatial territory swept out by DHA is good news for making certain areas of membranes more fluid or lipoprotein particles larger, even though it reduces the benefits of DHA in competing with AA for key enzymes important in the development of cellular inflammation.

Common Effects for Both EPA and DHA

Not surprisingly, there are some areas in which both EPA and DHA appear to be equally beneficial. For example, both are equally effective in reducing triglyceride levels (10). This is probably due to the relatively equivalent activation of the gene transcription factor (PPAR alpha) that causes the enhanced synthesis of the enzymes that oxidize fats in lipoprotein particles. There is also apparently equal activation of the anti-inflammatory gene transcription factor PPAR-gamma (11). Both seem to be equally effective in making powerful anti-inflammatory eicosanoids known as resolvins (12). Finally, although both have no effect on total cholesterol levels, DHA can increase the size of LDL particle to a greater extent than EPA can (10).

Summary

EPA and DHA do different things, so you need them both. If your goal is reducing cellular inflammation, then you probably need more EPA than DHA. How much more? Probably twice the levels, but you always cover your bets with omega-3 fatty acids by using both at the same time.

References

  1. Sears B. “The Zone.” Regan Books. New York, NY (1995)
  2. Chen CT, Liu Z, Ouellet M, Calon F, and Bazinet RP. “Rapid beta-oxidation of eicosapentaenoic acid in mouse brain: an in situ study.” Prostaglandins Leukot Essent Fatty Acids 80:157-163 (2009)
  3. Chen CT, Liu Z, and Bazinet RP. “Rapid de-esterification and loss of eicosapentaenoic acid from rat brain phospholipids: an intracerebroventricular study. J Neurochem 116:363-373 (2011)
  4. Umhau JC, Zhou W, Carson RE, Rapoport SI, Polozova A, Demar J, Hussein N, Bhattacharjee AK, Ma K, Esposito G, Majchrzak S, Herscovitch P, Eckelman WC, Kurdziel KA, and Salem N. “Imaging incorporation of circulating docosahexaenoic acid into the human brain using positron emission tomography.” J Lipid Res 50:1259-1268 (2009)
  5. Martins JG. “EPA but not DHA appears to be responsible for the efficacy of omega-3 long chain polyunsaturated fatty acid supplementation in depression: evidence from a meta-analysis of randomized controlled trials.” J Am Coll Nutr 28:525-542 (2009)
  6. Sato M, Adan Y, Shibata K, Shoji Y, Sato H, and Imaizumi K. “Cloning of rat delta 6-desaturase and its regulation by dietary eicosapentaenoic or docosahexaenoic acid.” World Rev Nutr Diet 88:196-199 (2001)
  7. Stillwell W and Wassall SR. “Docosahexaenoic acid: membrane properties of a unique fatty acid. Chem Phys Lipids 126:1-27 (2003)
  8. Chapkin RS, McMurray DN, Davidson LA, Patil BS, Fan YY, and Lupton JR. “Bioactive dietary long-chain fatty acids: emerging mechanisms of action.” Br J Nutr 100:1152-1157 (2008)
  9. Li Q, Wang M, Tan L, Wang C, Ma J, Li N, Li Y, Xu G, and Li J. “Docosahexaenoic acid changes lipid composition and interleukin-2 receptor signaling in membrane rafts.” J Lipid Res 46:1904-1913 (2005)
  10. Mori TA, Burke V, Puddey IB, Watts GF, O’Neal DN, Best JD, and Beilin LJ. “Purified eicosapentaenoic and docosahexaenoic acids have differential effects on serum lipids and lipoproteins, LDL particle size, glucose, and insulin in mildly hyperlipidemic men.” Am J Clin Nutr 71:1085-1094 (2000)
  11. Li H, Ruan XZ, Powis SH, Fernando R, Mon WY, Wheeler DC, Moorhead JF, and Varghese Z. “EPA and DHA reduce LPS-induced inflammation responses in HK-2 cells: evidence for a PPAR-gamma-dependent mechanism.” Kidney Int 67:867-874 (2005)
  12. Serhan CN, Hong S, Gronert K, Colgan SP, Devchand PR, Mirick G, and Moussignac RL. “Resolvins: a family of bioactive products of omega-3 fatty acid transformation circuits initiated by aspirin treatment that counter proinflammation signals.” J Exp Med 1996:1025-1037
Share and Enjoy:
  • Print
  • Digg
  • StumbleUpon
  • del.icio.us
  • Facebook
  • Yahoo! Buzz
  • Twitter
  • Google Bookmarks

Related Posts:

This entry was posted in Zone Diet and tagged , , , , , by Dr. Barry Sears. Bookmark the permalink.

About Dr. Barry Sears

Dr. Barry Sears is a leading authority on the impact of the diet on hormonal response, genetic expression, and inflammation. A former research scientist at the Boston University School of Medicine and the Massachusetts Institute of Technology, Dr. Sears has dedicated his research efforts over the past 30 years to the study of lipids. He has published more than 30 scientific articles and holds 13 U.S. patents in the areas of intravenous drug delivery systems and hormonal regulation for the treatment of cardiovascular disease. He has also written 13 books, including the New York Times #1 best-seller "The Zone". These books have sold more than 5 million copies in the U.S. and have been translated into 22 different languages.

2 thoughts on “What are the real differences between EPA and DHA?

  1. Thank you for another clear, concise explanation.
    You have talked about (and in many cases made available): the benefits of eating vegetables and fruits for their phytols, minerals and other micronutrients (I might add also for their alkaline buffers for the uric acid produced by proteins.), of eating low density and resistant carbs to maintain insulin levels at a healthy range, and of the importance of high quality, balanced ratios) sources of omega-3 and omega-6 fatty acids.
    You also have discussed the importance of omega-6 fats for rejuvenation and essential levels of inflammation. You seems to recommend 1 < AA/EPA < 3.5 ratios with warnings that too low a ratio may lead to increased levels of strokes and lowered resistance to disease.
    I realize you are careful avoid dogma and too much theorizing where there is not solid research. But what concerns and recommendations would you tend to have for monitoring AA/EPA, insulin, etc for a tremendously fit 30 year old who collapsed with blood in the pericardium and was found to have an extremely aggressive, 1 cm by 5 cm cancerous tumour in the Right atrium and a 1.5 cm aggressive cancerous cyst in the right lung’s basal lobe. The atrial tumour had shrunk (after four pic line injected chemo treatments [normal is one to 2] by 50-65% but, tho a very young tumour, its progeny in the lung, to everyones’ dismay, had grown by 50% diameter during the chemo treatments (very unusually iso early in the game)and had to be surgically removed three weeks ago. Radiation, altho very difficult to reach in its location in the right atrium and the damage it will do to the heart muscle, will be necessary before surgical removal.
    The hope is mainly of increased quality of life and reduced seeding. There has yet to occur in the literature a remission—altho this is the earliest detection, is in the youngest and the fittest patient, and until the resistant lung cyst’s apparent mutation, there was a more optimistic future.
    The question is how does one balance rejuvenation and inflammation response when combining chemo, surgery, and radiation with diet? What ratios and numbers of concern besides AA/EPA would you suggest might well be considered?
    For several years he has followed a fairly strict zone diet with lots of fish, fish oil, coloured vegetables and fruit, and vigorous exercise.
    Has your AA/EPA test been approved yet? Is it available without approval?
    Are there any differences in your recommended ratios for the healthy person those who are following surgery, chemo, or radiation? What other tests do you recommend that might not be commonly given? We gave up corn oil, etc. after your publication of Toxic Fats. We are not expecting miracles but we also believe in giving the best assistance we can to medicine.
    Your zone eating, coloured fruits and vegetables, and 10 gms/day of EPA + DHA along with 4-6 hours have been a tremendous help in rebuilding me from TBI. Since using the zone diets, olive oil uncooked and Mazola oil for stir frying, with daily 10 gms EPA+DHA I hae had a tremendous improvement in IQ, balance, vision, and arthritis. (I spend 4-6 hrs/day doing exercises, visualizations, eye training etc.) It ahd been slowly and steadily improving before I was introduced to your approach. Thank you.

    • Having gone through several situations recently that remind me that we are all completely mortal and are subject to random strikes of lightning, my heart goes out to you.

      I am grateful you’ve chosen to discuss this situation in public and am looking forward to Dr. Sears’ response.

      I hope your recovery is quick and complete.

Leave a Reply

Your email address will not be published. Required fields are marked *

You may use these HTML tags and attributes: <a href="" title=""> <abbr title=""> <acronym title=""> <b> <blockquote cite=""> <cite> <code> <del datetime=""> <em> <i> <q cite=""> <strike> <strong>