Fish oil and EPA may not be best for the heart.
Fish for the heart first gained popularity in 1969 when two Danish physicians determined that the Eskimo population in Greenland had a much lower death rate from heart disease than the rest of the Danish population. They concluded that the reason for this had to be the high consumption of fish. Since then, fish has been “studied to death”.
As a result of all these intense fish studies, it has been the common belief that EPA was best for the heart while DHA was best for the brain. For many years, it was believed that the main benefits of fish oils for the heart came from EPA because of its role in modulating eicosanoids (a class of cytokines which have hormone-like actions that increase LDL or bad cholesterol levels). Because of this, typical omega-3 fish oil products contain higher concentrations of EPA than DHA.
However, new research is showing that DHA offers greater cardiovascular benefits than EPA. DHA regulates healthy blood pressure whereas the same amount of EPA cannot. In addition, DHA boosts the good HDL cholesterol while lowering the bad LDL triglycerides, something also associated with insulin resistance.
One interesting study out of Finland showed that, although DHA and not EPA was instrumental in the considerable lowering of the risk factor for CHD, consuming that amount of fish also dramatically increased the mercury content in their bodies.1 Another study, involved Mediterranean men with CHD who had significantly lower omega-3s in their blood than other men free of the disease. The difference was found to be DHA (and DPA) but not EPA.2
The reasons behind DHA being more effective than EPA are attributed to its functions. DHA is vital in preventing arrhythmias, regulating blood pressure, and for boosting the good HDL cholesterol. A low HDL level is not only linked to heart disease and metabolic syndrome X (a group of risk factors that determine if one is prone to heart disease), but is also associated with insulin resistance and diabetics are known to be at a higher risk for CHD.
Because of its preformed omega-3 fatty acids, fish oil is often taken to reduce cholesterol; but fish oil contains cholesterol because it is an animal product. Amounts vary, however. For instance, 100 grams of sardine oil contains about 710 mg. cholesterol, salmon oil – 485 mg, menhaden oil – 521 mg, herring oil – 766 mg, cod liver oil – 570 mg, and trout meat contains 58 mg.3
For some people, taking large amounts of fish oil may be effective in lowering triglyceride levels but, for others, fish oil increased LDL levels.4 For these people, it took the addition of 15 grams of pectin per day5 and garlic supplementation to lower the LDL levels.6 Usually any triglyceride-lowering effect can be attributed to replacing meat and other saturated fatty sources with fish. The same thing would happen if these saturated fatty sources were replaced with beans or other vegetable proteins. Plant-based oils, on the other hand, contain no cholesterol.
Fish oil simply is not needed to reduce the risk of heart disease, which has been noticed in the vegetarian community. Diet and the use of plant-based oils have long proven to be more effective in the long run. Although one study recommended fish (with a note of caution because of such pollutants as mercury), it did state that for vegetarians or nonfish eaters, a total daily intake of 1.5 to 3 g per day of ALA seemed to be beneficial.7
As confirmation, a flurry of controlled studies has determined that consumption of ALA omega-3 fatty acids, rather than fish oil, is associated with the reduced risk of CHD (coronary heart disease).8 to 22 Furthermore, one study went so far as to suggest that the percentage of DHA in erythrocytes could be used as an indicator of risk for CHD23 since it is DHA and not EPA that raises HDL cholesterol levels.
One study to watch for is currently being carried out at the St. Boniface General Hospital Research Centre in Winnipeg, Canada. One of their projects includes the effects of fish oil, flaxseed oil, and hempseed oil supplementation on plasma lipids, LDL oxidation, inflammatory profile, and platelet function in healthy humans.24
References
- 1Rissanen, Voutilainen, Nyyssonen, Lakka, and Salonen. 2000. “Fish oil-derived fatty acids, docosahexaenoic acid and docosapentaenoic acid, and the risk of acute coronary events: the Kuopio ischaemic heart disease risk factor study.” Circulation 102(22): 2677-9.
- 2Mori, Bao, Burke, Puddey, and Beilin. 1999. “Docosahexaenoic acid but not eicosapentaenoic acid lowers ambulatory blood pressure and heart rate in humans” Hypertension 34(2):253-60.
- 3USDA. Nutrient Database for Standard Reference, release 14. 1999.
http://www.nal.usda.gov/fnic/foodcomp/search/ - 4Harris, Zucker, Dujovne. 1988. “Omega-3 fatty acids in type IV hyperlipidemia: triglycerides vs methyl esters.” American Journal of Clinical Nutrition 48(4): 992-97 [abstr].
- 5Sheehan JP, Wei IW, Ulchaker M, Tserng KY. “Effects of high fiber intake in fish oil-treated patients with non-insulin-dependent diabetes mellitus.” American Journal of Clinical Nutrition 1997; 66:11837.
- 6Adler AJ, Holub BJ. “Effects of garlic and fish-oil supplementation on serum lipid and lipoprotein concentrations in hypercholesterolemic men.” American Journal of Clinical Nutrition 1997; 65:44550.
- 7Kris-Etherton, Harris, and Appel LJ. 2002. “Fish consumption, fish oil, omega-3 fatty acids, and cardiovascular disease.” Circulation 106(21):2747-57.
- 8Longeril, Renaud, Mamelle, Salen, Martin, Monjaud, Guidollet, Touboul, and Delaye. 1994. “Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease.” Lancet 343:1454-59.
- 9Simon, Fong, Bernert, and Browner. 1995. “Serum fatty acids and the risk of stroke.” Stroke 26:778-82.
- 10Ferretti and Flanagan. 1996. “Anti tromboxane activity of dietary alpha-linolenic acid: a pilot study.” Prostaglandins, Leukotrienes, and Essential Fatty Acids 54(6):451-55.
- 11Loria and Padgett. 1997. “Alpha-linolenic acid prevents the hypercholesteremic effects of cholesterol addition to a corn diet.” Nutritional Biochemistry 8:140-46.
- 12Li, Sinclair, Wilson, Nakkote, Kelly, Abedin, Mann, and Turner. 1999. “Effect of dietary alpha-linolenic acid on thrombotic risk factors in vegetarian men.” American Journal of Clinical Nutrition 69:872-82.
- 13Hu, Stampfer, Manson, Rimm, Wolk, Colditz, Hennekens, and Willet. 1999. “Dietary intake of alpha-linolenic acid and risk of fatal ischemic heart disease among women.” American Journal of Clinical Nutrition 69:890-97.
- 14Guallar, Aro, Jiménez, Martin-Moreno, Salminen, vant Veer, Kardinaal, Gomez-Aracena, Martin, Kohlmeier, Kark, Mazaev, Ringstad, Guillen, Riemersma, Huttunen, Thamm, and Kok. 1999. “Omega-3 fatty acids in adipose tissue and risk of myocardial infarction: the EURAMIC study.” Arteriosclerosis, Thrombosis, and Vascular Biology 19:1111-18.
- 15Von Sharky, Angerer, Kothny, Theisen, and Mudra. 1999. “The effect of dietary omega-3 fatty acids on coronary atherosclerosis.” Annals of Internal Medicine 130:554-62.
- 16GISSI (Gruppo Italiano per lo Studio della Sopravvivenza nell’Infarto miocardico). 1999. “Dietary supplementation with n-3 polyunsaturated fatty acids and vitamin E after myocardial infarction: results of the GISSI-Prevenzione trial.” Lancet 3554:447-55.
- 17Mantzioris, Cleland, Gibson, Neumann, Demasi, and James. 2000. “Biochemical effects of a diet containing foods enriched with n-3 fatty acids.” American Journal of Clinical Nutrition 72:42-48.
- 18Iso, Raxrode, Stampfer, Manson, Colditz, Speizer, Hennekens, and Willet. 2001. “Intake of fish oil and omega-3 fatty acids and risk of stroke in women.” Journal of the American Medical Association 285(3):304.
- 19Ridges, Sunderland, Moerman, Meyer, Astheimer, and Howe. 2001. “Cholesterol lowering benefits of soy and linseed enriched foods.” Asian Pacific Journal of Nutrition 10(3):204-11.
- 20Djousse, Folsom, Province, Hunt, and Curtis-Ellison. 2003. “Dietary linolenic acid and carotid atherosclerosis: the National Heart, Lung, and Blood Institute family health study.” American Journal of Clinical Nutrition 77:819-25.
- 21McLennan, Howe, Abeywardena, Muggli, Raederstorff, Mano, Rayner, and Head. 1996. “The cardiovascular protective role of docosahexaenoic acid.” European Journal of Pharmacology 300(1-2): 83-9.
- 22Buckley, Shewring, Turner, Yaqoob, and Minihane. 2004. “Circulating triacylglycerol and apoE levels in response to EPA and docosahexaenoic acid supplementation in adult human subjects.” British Journal of Nutrition 92(3):477-83.
- 23Paganelli, Maixent, Duran, Parhizgar, Pieroni, and Sennoune. “Altered erythrocyte n-3 fatty acids in Mediterranean patients with coronary artery disease.” International Journal of Cardiology 78(1): 27-32.
- 24Agriculture Canada. “Functional Foods and Nutraceuticals.”
This page was researched in November 2005.
