Am I getting enough omega-3 fatty acids from my diet?
This is one of the most commonly asked questions about omega-3 fatty acids, and it naturally begs the question "what is enough?" Although the answer is and will continue to be the subject of intense investigation, in 2004 an important paper was published that will help define "enough." Harris and von Schacky proposed a new blood test called "the omega-3 index," and presented a case for why it should be considered as a new risk factor for fatal coronary heart disease 1. The omega-3 index is the amount of long-chain omega-3 fatty acids (eicosapentaenoic acid and docosahexaenoic acid, EPA and DHA, respectively) in the red blood cell (RBC) membranes, and it is expressed as a percentage of total RBC fatty acids. Their proposal, that low omega-3 indexes would predict increased heart disease risk, was based in part on the studies of Siscovick et al. 2 and Albert et al. 3. These groups reported powerful relationships between the omega-3 index and risk for primary cardiac arrest [or for Albert et al., between whole blood EPA + DHA + docosapentaenoic acid (DPA) and sudden cardiac death (SCD)].
Harris and von Schacky suggested preliminary cut-points defining high-, intermediate- and low-risk categories for the omega-3 index as <4%, 4%-8%, >8%, respectively. These were derived from a review of the available literature, and have since been confirmed in a large case-control study in acute coronary syndrome patients 4, as well as by studies in Japan where SCD is very rare and the average omega-3 index is 8.5% 5. Further studies are nevertheless needed to more precisely define target values, not only for CHD endpoints, but for other conditions (e.g., dementia 6,7 or macular degeneration 8) where omega-3 insufficiency may have pathological significance.
As this idea has begun to catch on, a variety of laboratories have started to offer omega-3 blood tests for use in research and clinical care of patients (please see references). Thus, the answer to "what is enough omega-3 fatty acids?" may end up being "that amount of omega-3 fatty acids that allows you to achieve an omega-3 index of 8% or greater."
References
- Harris WS, von Schacky C. The Omega-3 Index: a new risk factor for death from coronary heart disease? Prev Med 2004;39:212-220.
- Siscovick DS, Raghunathan TE, King I, Weinmann S, Wicklund KG, Albright J, Bovbjerg V, Arbogast P, Smith H, Kushi LH, Cobb LA, Copass MK, Psaty BM, Lemaitre R, Retzlaff B, Childs M, Knopp RH. Dietary intake and cell membrane levels of long-chain n-3 polyunsaturated fatty acids and the risk of primary cardiac arrest. J Am Med Assoc 1995;274:1363-1367.
- Albert CM, Campos H, Stampfer MJ, Ridker PM, Manson JE, Willett WC, Ma J. Blood levels of long-chain n-3 fatty acids and the risk of sudden death. N Engl J Med 2002;346:1113-1118.
- Block RC, Harris WS, Reid KJ, Sands SA, Spertus JA. EPA and DHA in Blood Cell Membranes from Acute Coronary Syndrome Patients and Controls. Atherosclerosis 2007;197:821-828.
- Itomura M, Fujioka S, Hamazaki K, Kobayashi K, Nagasawa T, Sawazaki S, Kirihara Y, Hamazaki T. Factors influencing EPA+DHA levels in red blood cells in Japan. In Vivo 2008 Jan -Feb ;22 (1):131 -5 2008;22:131-135.
- Barberger-Gateau P, Raffaitin C, Letenneur L, Berr C, Tzourio C, Dartigues JF, Alperovitch A. Dietary patterns and risk of dementia: the Three-City cohort study. Neurology 2007;69:1921-1930.
- Schaefer EJ, Bongard V, Beiser AS, Lamon-Fava S, Robins SJ, Au R, Tucker KL, Kyle DJ, Wilson PW, Wolf PA. Plasma phosphatidylcholine docosahexaenoic acid content and risk of dementia and Alzheimer disease: the Framingham Heart Study. Arch Neurol 2006;63:1545-1550.
- Chong EW, Kreis AJ, Wong TY, Simpson JA, Guymer RH. Dietary omega-3 fatty acid and fish intake in the primary prevention of age-related macular degeneration: a systematic review and meta-analysis. Arch Ophthalmol 2008 Jun ;126 (6 ):826 -33 2008;126:826-833.
Key Points
- Deficiencies in the omega-3 fatty acids EPA and DHA are associated with increased risk for fatal coronary heart disease.
- The omega-3 index, which is the amount of long-chain omega-3 fatty acids (EPA and DHA) measured in red blood cells, is used to determine if you are consuming enough of these fatty acids to reduce your risk of coronary heart disease.
- A low omega-3 index places a person at higher risk for developing coronary heart disease.
- Several laboratories in the US and Canada now offer the omega-3 index test.
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