A type of polyunsaturated fatty acid (PUFA) derived mainly from fish oil. Anecdotally, omega-3 fatty acids are used to treat depression, hypercholesterolemia and to reduce the risk of heart attack. A large survey of Finnish adults found that depressive symptoms were significantly higher among infrequent fish consumers 1 and other studies have shown that individuals with major depression have marked depletions in omega-3 fatty acids 2. Omega-3 fatty acid supplementation lowered triglyceride levels in people with type 2 diabetes mellitus, however, low density lipoprotein cholesterol levels were increased 3. Omega-3 fatty acids may also help patients with ulcerative colitis 4 and may reduce colon cancer risk 5 . Omega-3 may be useful as a perioperative supplement as it lowers the magnitude of the body's inflammatory response 6. It has been shown not to reduce coagulation and platelet function after surgery 7. Omega-3 fatty acids can reduce sunburn sensitivity 8. Reviews of trials using omega-3 fatty acids have shown possible benefits for patients with cystic fibrosis 9, but no benefit for patients with asthma 10. Only mixed results were seen in patients with schizophrenia 11. Results from a recent clinical trial suggest that dietary supplementation with fish oil may help reduce the symptoms of systemic lupus erythematosus 19 . The FDA recommended that the consumption of fish oils be limited to 3 grams or less per day as higher doses may increase the risk of bleeding. 18
Food Sources
- Fish Oil
- Cod Liver Oil
- Flaxseed Oil
- Linseed Oil
Purpoted Uses
- Asthma
- Atherosclerosis
- Cancer prevention
- Cardiovascular disease
- Colitis
- Cystic fibrosis
- Depression
- High cholesterol
- Schizophrenia
Constituents
Fatty Acids including: Eicosapentaenoic (EPA), Docosahexaenoic (DHA), Myristic, Palmitric, Palmitoleic, Stearic, Oleic, Linoleic, Linolenic, Stearidonic, Eicosaenoic, Arachidonic, Docosaenoic and docosapentaenoic (DPA) 7.
Mechanism of Action
Omega-3 fatty acids are a type of polyunsaturated fatty acid containing two or more double bonds in their acyl chain and a double bond on carbon number 3 12. Changes in omega-3 fatty acid levels have been associated with cardiovascular disease and depression 13 . The cardioprotective effects of omega-3 likely come from its ability to be incorporated into and thereby enhance the stability of atherosclerotic plaques 12. Omega-3 fatty acid does not seem to affect platelet function or coagulation 7. Increasing the intake of polyunsaturated fatty acids has been shown to increase lipid peroxidation. Supplementation with omega-3 fatty acids, therefore, may increase the oxidative stress on the body. Studies have shown that mucosal alpha-tocopherol levels decrease upon omega-3 supplementation which researchers believe may result from the body's attempt to counteract the added oxidative burden 5. Besides reducing serum anti-oxidant levels, little is known about how this added oxidative stress affects the body. Omega-3 fatty acid supplementation has been shown to decrease IL-6 levels 6 and tumor necrosis factor-alpha 14 while leaving most other mononuclear cell functions unaffected 15. Omega-3 fatty acids may also reduce inflammation in patients with ulcerative colitis by reducing rectal dialysate leukotriene B4 4. Because of its anti-inflammatory effects, Omega-3 fatty acids have been thought to benefit patients with asthma 10 and cystic fibrosis 9, however studies are inconclusive. Increasing PUFA intake in pregnant women increases PUFA concentration but not cytokine concentration in human milk 16. Omega-3 fatty acid supplementation provides protection against ultra-violet radiation induced erythema and p53 expression, a biomarker of DNA damage 8.
Adverse Reactions
Reported: Fishy aftertaste 5, loose stools and nausea 17 after large doses.
Drug Interactions
May increase the effect of other anticoagulant/antiplatelet agents.
Lab Interactions
- May reduce levels of alpha-tocopherol and beta-carotene 5 14.
- High levels of omega-3 fatty acids may decrease triglyceride and increase LDL cholesterol levels 3.
- Doses higher than 3 grams per day may increase bleeding time 18.
Literature Summary and Critique
Thies F, Garry JM, Yaqoob P, Rerkasem K, Williams J, Shearman CP et al. Association of n-3 polyunsaturated fatty acids with stability of atherosclerotic plaques: a randomised controlled trial. Lancet 2003;361:477-85.
A randomized controlled trial of polyunsaturated fatty acids and stability of atherosclerotic plaques. 188 patients awaiting carotid endarterectomy were randomized to receive sunflower oil (high omega-6 concentration), fish oil (high omega-3 concentration) or control oil until surgery. Each patient consumed six capsules per day each containing 1 g of oil and 1 mg alpha-tocopherol. Duration of treatment ranged from seven to 189 days with a median of 42 days. Patients receiving the fish oil supplementation were found to have readily incorporated omega-3 polyunsaturated fatty acids in their atherosclerotic plaques thereby enhancing the stability of the plaques. Patients receiving either sunflower oil or control had no change in fatty-acid composition or atherosclerotic stability during the course of treatment. Researchers believe that this stability of plaques may explain the reductions in cardiovascular events associated with omega-3 polyunsaturated fatty acid intake.
Stenson WF, Cort D, Rodgers J, Burakoff R, DeSchryver-Kecskemeti K, Gramlich TL et al. Dietary supplementation with fish oil in ulcerative colitis. Ann.Intern.Med 1992;116:609-14.
A multicenter, randomized, double-blind, placebo-controlled, crossover trial of fish oil and ulcerative colitis. 24 patients with ulcerative colitis were randomized to receive 18 Max-EPA capsules (3.24 g EPA and 2.6 g DHA) or 18 placebo capsules containing corn oil per day. Patients continued treatment for four months and after a washout period of one month, reversed treatment. Patients observed a statistically significant weight gain and reduction in acute histology index as well as rectal dialysate levels of leukotriene B4 during treatment.
Farmer A, Montori V, Dinneen S, Clar C. Fish oil in people with type 2 diabetes mellitus. Cochrane. Database.Syst.Rev. 2001;CD003205.
A systematic review of fish oil on cholesterol levels in people with type 2 diabetes mellitus including eighteen trials and 823 participants. Doses of fish oil ranged from 3 to 18 grams/day. Meta-analysis showed a statistically significant effect of fish oil in lowering triglycerides by 0.56 mmol/l and raising LDL cholesterol by 0.21 mmol/l. No statistically significant effect was observed for fasting glucose, HbA1c, total or HDL cholesterol. The effects on triglycerides and LDL cholesterol were more marked in recruited people with hypertriglyceridemia and in those trials using higher doses of fish oil. No adverse effects were reported. Researchers note that no trials with vascular or mortality defined endpoints were found.
Beckles WN, Elliott TM, Everard ML. Omega-3 fatty acids (from fish oils) for cystic fibrosis. Cochrane.Database.Syst.Rev. 2002;CD002201.
A systematic review of omega-3 fatty acids for cystic fibrosis including two trials and a total of 31 participants. Both trials compared omega-3 fatty acids to olive oil controls for six weeks. One study showed an improvement in FEV1, FVC, Schwachman score and reduction in sputum volume in the fish oil group. Larger, long-term, multi-center trials are needed to corroborate this evidence.
Woods RK, Thien FC, Abramson MJ. Dietary marine fatty acids (fish oil) for asthma in adults and children. Cochrane.Database.Syst.Rev. 2002;CD001283.
A systematic review of trials of omega-3 fatty acids for asthma in participants over two years of age that were at least four weeks in duration. The review included nine trials. No consistent effect on any of the following outcomes was observed: FEV1, peak flow rate, asthma symptoms, asthma medication use or bronchial hyper reactivity. One study which combined dietary manipulation with fish oil supplementation demonstrated improvement in peak flow and a reduction in asthma medication use, however the researchers concluded that there is little evidence to recommend omega-3 fatty acids to improve asthma control. No adverse effects were reported.
Joy CB, Mumby-Croft R, Joy LA. Polyunsaturated fatty acid supplementation for schizophrenia. Cochrane.Database.Syst.Rev. 2003;CD001257.
A systematic review of trials of polyunsaturated fatty acids for schizophrenia included including five small, short studies including 313 participants. One small study suggested that EPA enriched oil may have some antipsychotic properties when compared with placebo, however most trials were too small to show significant effect. Some of the trials included omega-6 fatty acid supplementation. Researchers conclude that larger, well designed studies are needed.
Duffy EM et al. The clinical effect of dietary supplementation with omega-3 fish oils and/or copper in systemic lupus erythematosus. J. Rheumatology. 2004;31(8):1551-6.
A double blind, double placebo controlled trial. 52 SLE patients were randomly assigned to 4 treatment groups that received 3 g fish oil and 3 g of copper, 3 g fish oil and placebo copper, 3 g copper and 3 g placebo fish oil, or both placebo capsules. Researchers found a significant reduction in symptoms of SLE in patients who took fish oil capsules compared to those on placebo. There was no measurable effect on symptoms in patients who took copper. Larger trials are needed to support this claim.