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Fish oil is derived from the flesh of fatty fish (e.g. salmon herring, mackerel, pilchards, sardines, trout). It is particularly rich in omega 3 fatty acids EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid). These fatty acids are converted by the body into the beneficial series 3 prostaglandins.
Fish liver oils are derived from the livers of white fish, such as cod and halibut. Fish liver oils contain vitamins A and D, and should be used with caution by certain groups of people.
Alpha-linolenic acid (ALA) is present in green leafy vegetables, linseed (flax) oil, soy oil, etc. However, even if our diet is very rich in these, we may still be deficient in series 3 prostaglandins because the enzymes needed to convert ALA into EPA are only weakly active.
Dietary EPA can therefore be extremely valuable because it skips this step and provides a material from which series 3 prostaglandins can easily be produced.
The real value of fish oil lies in its EPA and DHA content.
Essentially the pathway goes as follows: Alpha linolenic acid (ALA) is converted into stearidonic acid (SA), which is then turned into eicosatetraenoic acid (ETA). ETA is transformed into eicosapentaenoic acid (EPA). EPA is then converted to either docosapentaenoic acid (DPA), or prostaglandin series 3. DPA proceeds to become docosahexaenoic acid (DHA).
Fish oils have been found to have significant benefits on heart health, including:
- Altering the balance of blood fats in a favourable way (1).
- Reducing the likelihood of blood clotting (2).
- Making the heart less prone to arrhythmias (irregular heartbeats) (3).
- Reducing the viscosity of the blood, thereby facilitating blood flow (4).
Fish oil may also help to prevent heart disease by raising beneficial HDL cholesterol, reducing homocysteine levels, and reducing Hypertension (5-14).
Pregnant women are advised to keep up their intake of omega 3 fatty acids by eating oily fish or taking low level fish oil supplements if necessary. This is because more and more research is showing how vitally important omega 3 fatty acids are for the brain development of the foetus (15).
Improvements in the symptoms of rheumatoid arthritis have been reported in patients taking fish oil supplements (16-18). Fish oil therapy is free from side effects and may also enhance the effects of conventional drugs (19).
Regular use of fish oil may be beneficial to women who experience menstrual Cramps (20).
A recent study reported very significant benefits for patients with bipolar disease (a manic depressive psychosis)(21).
Essential Fatty Acids present in fish oil may help treat osteoporosis when taken with Calcium supplements. Studies show that women who take fish oil with calcium have better bone density and fewer Fractures than women who take calcium alone (22,23).
Fish oil has been used in very high amounts in clinical research without any overt toxicity symptoms. However, when taking high levels of fish oil, patients should be monitored by a medical professional, because omega 3 fatty acids can displace omega 6 fatty acids from cell membranes. There may also be a thinning of the blood and a reduction in clotting time.
When taking fish liver oils, it is very important that Vitamin A and Vitamin D intake is checked to ensure that one does not exceed upper safe levels. This is because the vitamins are fat-soluble, which means that taking fish oil increases the chance of excess amounts building up in the body. When taking cod liver oil, pregnant women should take no more than 2500i.u. vitamin A a day, while other individuals should not exceed 7500i.u. Vitamin D consumption should not exceed 10µg from supplements.
INTERACTIONS AND CONTRA-INDICATIONS
Evening Primrose Oil:
Fish oils and Evening Primrose Oil can suitably be supplemented together to achieve a balance of the two families of fatty acid (omega 6 and omega 3). However, alpha linolenic acid (ALA) and GLA/linoleic acid combinations are conflicting, as the former blocks the further conversion of the latter two.
Occasionally, fish oils may cause nausea when first taken. This symptom quickly subsides over a period of time and can be lessened by taking with a meal.
High dose fish oils should be avoided by those on blood thinning drugs such as warfarin and heparin.
1. Agren JJ, et al. Fish diet, fish oil and docosahexaenoic acid rich oil lower fasting and postprandial plasma lipid levels. Eur J Clin Nutr, 50;11:765-771 1996.
2. Mori TA, et al. Interactions between dietary fat, fish and fish oils and their effects on platelet function in men at risk of cardiovascular disease. Atrerioscler Thromb Vasc Biol, 17;2:279-286 1997.
3. Kang JX, Leaf A. The cardiac antiarrhythmic effects of polyunsaturated fatty acid. Lipids, 31 suppl:S41-44 1996.
4. Semplicini A, Valle R. Fish oils and their possible role in the treatment of cardiovascular diseases. Pharmacol Ther, 61;3:385-397 1994.
5. Shekelle RB, et al. Diet, serum cholesterol, and death from Coronary Heart Disease. The Western Electric Study. N Engl J Med 304: 65, 1981.
6. Kromhout D, Arntzenius AC, Kempen-Voogd N, et al. The inverse relation between fish consumption and twenty year mortality from Coronary Heart Disease. N Engl J Med 312: 1205, 1985.
7. Harris WS. N-3 fatty acids and serum lipoproteins: human studies. Am J Clin Nutr 65(suppl.): 1645S-1654S, 1997.
8. Cobiac L, Clifton PM, and Abbey M. Lipid, lipoprotein, and hemostatic effects of fish vs fish-oil n-3 fatty acids in mildly hyperlipidemic males. Am J Clin Nutr 53: 1210-1216, 1991.
9. Dyerberg, J. N-3 fatty acids and coronary artery disease. Potentials and problems. Omega-3, Lipoproteins, and Atherosclerosis 27: 251-258, 1996.
10. Lungershausen YK, Abbey M, Nestel PJ, and Howe PR. Reduction of blood pressure and plasma triglycerides by omega-3 fatty acids in treated hypertensives. J Hypertens 12: 1041-1045, 1994.
11. Radack K, Deck C, and Huster G. The effects of low doses of n-3 fatty acid supplementation on blood pressure in hypertensive subjects. A randomized controlled trial. Arch Intern Med 151: 1173-1180, 1991.
12. Singer P, et al. Lipid and blood-pressure lowering effect of mackerel diet in man. atherosclerosis 49: 99, 1983.
13. Singer P, Melzer S, Goschel M, and Augustin S. Fish oil amplifies the effect of propranolol in mild essential hypertension. Hypertension 16: 682-691, 1990.
14. Whelton PK, Kumanyika SK, and Cook NR. Efficacy of nonpharmacologic interventions in adults with high-normal blood pressure: results from phase 1 of the Trials of Hypertension Prevention. Trials of Hypertension Prevention Collaborative Research Group. Am J Clin Nutr 65: 652S-660S, 1997.
15. Eur J Clin Nutr, 1997,51;8:548-553.
16. Cleland LG, et al. Clinical and biochemical effects of dietary fish oil supplements in rheumatoid arthritis. J Rheumatology, 15:1471-1475 1988.
17. Kremer JM, et al. Dietary fish oil and olive oil supplementation in patients with rheumatoid arthritis. Arthritis and Rheumatism, 33:810-820 1990.
18. Nielsen GL, et al. The effects of dietary supplementation with n-3 polyunsaturated fatty acids in patients with rheumatoid Arthritis: a randomized, double blind trial. Eur J Investigation, 22:687-691 1992.
19. James MJ and Cleland LG. Dietary n-3 fatty acids and therapy for rheumatoid arthritis. Semin Arthritis Rheum 27: 85-97, 1997.
20. Harel Z, Biro FM, Kottenhahn RK, et al. Supplementation with omega-3 polyunsaturated fatty acids in the management of dysmenorrhea in adolescents. Am J Obstet Gynecol 174: 1335-1338, 1996.
21. Andrew L. Stoll, director of psychopharmacology research at Harvard Medical School/McClean Hospital. Unpublished communication.
22. Kruger MC, et al. Calcium, gamma-linolenic acid (GLA) and eicosapentaenoic acid (EPA) supplementation in Osteoporosis. Osteoporosis Int 6(suppl. 1): 250, 1996.
23. van Papendorp DH, Coetzer H, and Kruger MC. Biochemical profile of osteoporotic patients on essential fatty acid supplementation. Nutr Res 15: 325-334, 1995.