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Omega-3 fatty acids have gained popularity over the past decade as growing scientific evidence supports their use in preventing cardiovascular disease, depression, rheumatoid arthritis, and asthma, and in slowing cognitive decline. Because they are essential and cannot be synthesized in the human body, omega-3 fatty acids should be obtained through diet by consuming fish and nuts, or in supplemental form.

The American Heart Association recommends intake of fatty fish at least twice a week.

Patients taking anticoagulant or antiplatelet drugs should use caution, as omega-3 fatty acids can have additive effects.

ALSO KNOWN AS: Omegaven, Max-EPA

SUMMARY: Omega-3 fatty acids are essential compounds involved in several important physiologic processes. They are not synthesized in the body but can be obtained through diet or by taking dietary supplements. Fatty fish and nuts are excellent sources of omega-3.

There are three types of omega-3 fatty acids: alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), and docosahexaenoic acid (DHA). Following ingestion, ALA is converted to EPA and DHA, forms that are readily used by the body.

Omega-3 fatty acids have been extensively researched, and there is strong evidence of their effectiveness in preventing cardiovascular disease. Benefits were also seen in patients with depression, rheumatoid arthritis, cystic fibrosis, and systemic lupus erythematosus. In addition, omega-3 fatty acids confer neuroprotective effects by slowing cognitive decline in elderly individuals.[1]

The role of omega-3 in cancer prevention is inconclusive: Supplementation was shown to reduce risk of colon cancer,[2] but a systematic review of studies did not find a significant effect on lowering cancer incidence.[3] Further, higher intake of alpha-linolenic acid led to an increased risk of advanced prostate cancer in patients with low-grade disease.[4] More studies are needed.

ADVERSE REACTIONS: Fishy aftertaste,[2] loose stools, and nausea[5] have been reported following intake of large doses. Fish oil can have additive anticoagulant/antiplatelet effects.[6]

LAB INTERACTIONS: Omega-3 fatty acids reduce levels of alpha-tocopherol and beta-carotene.[2,7] High levels of omega-3 fatty acids may decrease triglyceride and increase LDL cholesterol levels.[8] Doses higher than 3 grams per day may increase bleeding time.[9]

Consumption of omega-3 fatty acids helps prevent a range of medical problems such as heart disease, depression, rheumatoid arthritis, and asthma.
The role of omega-3 in cancer prevention is inconclusive.
Omega-3 fatty acids are abundant in fatty fish such as mackerel, lake trout, herring, sardines, albacore tuna, salmon, and in walnuts and flaxseed.
Patients should discuss use of omega-3 supplements with their physicians because high doses can increase bleeding time.
For additional information visit the Memorial Sloan-Kettering Cancer Center Integrative Medicine Service website, “About Herbs” at http://www.mskcc.org/AboutHerbs.



1. Fetterman Jr JW, Zdanowicz MM: Therapeutic potential of n-3 polyunsaturated fatty acids in disease. Am J Health-Syst Pharm 66:1169-1179, 2009.

2. Anti M, Armelao F, Marra G, et al: Effects of different doses of fish oil on rectal cell proliferation in patients with sporadic colonic adenomas. Gastroenterology 107:1709-1718, 1994.

3. MacLean CH, Newberrt SJ, Mojica WA, et al: Effects of omega-3 fatty acids on cancer risk. JAMA 295:403-415, 2006.

4. Giovannucci E, Liu Y, Platz EA, et al: Risk factors for prostate cancer incidence and progression in the health professionals follow-up study. Int J Cancer 121:1571-1578, 2007.

5. Fugh-Berman A, Cott JM: Dietary supplements and natural products as psychotherapeutic agents. Psychosom Med 61:712-728, 1999.

6. Haller C, Kearney T, Bent S, et al: Dietary supplement adverse events: Report of a one-year poison center surveillance project. J Med Toxicol 4:84-92, 2008.

7. Holm T, Berge RK, Andreassen AK, et al: Omega-3 fatty acids enhance tumor necrosis factor-alpha levels in heart transplant recipients. Transplantation 72:706-711, 2001.

8. Farmer A, Montori V, Dinneen S, et al: Fish oil in people with type 2 diabetes mellitus. Cochrane Database Syst Rev CD003205, 2001.

9. Lewis CJ: Letter regarding dietary supplement health claim for omega-3 fatty acids and coronary heart disease. FDA Docket No. 91N-0103, October 31, 2000. Available at http://www.fda.gov/ohrms/dockets/DOCKETS/95s0316/95s-0316-Rpt0272-38-Appendix-D-Reference-F-FDA-vol205.pdf. Accessed December 21, 2009.

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