Heart Health: Can Fish Oil Reduce Heart Problems?
In the 1980s, researchers first began noticing the native Inuit (Eskimo) populations of Greenland and Alaska had a very low occurrence of heart disease despite a very high-fat diet. The researchers discovered the oils in the deepwater fish these people consumed (and continue to eat to this day) are rich in omega-3 polyunsaturated fatty acid. 1,2
These early scientific observations spawned extensive study and led to the current understanding of how important fish oil is to heart health.
Questions And Answers
While we generally think of fats as harmful, there are fats that actually have health benefits. The key is to learn the difference between the "good" fats and the "bad" ones. All natural fats are mixtures of different types of fatty acids. Fatty acids are made up of carbon atoms comprised of short or long chains. Each carbon atom has four bonding sites (similar to imaginary arms) where it can attach to other atoms. If all binding sites are attached to hydrogen atoms, the fatty acid chain is saturated. 3,4
If some binding sites on a carbon atom are attached to a neighboring carbon (made with a double bond), the fatty acid chain is unsaturated. If a fatty acid chain has two or more double bonds, it is called polyunsaturated. 4,5 Polyunsaturated fatty acids are further classified by where on the carbon chain the double bond is located. Linoleic acid is a polyunsaturated fatty acid with the first double bond located at the sixth carbon atom from the omega end; thus, it is an omega-6 fatty acid. 4,5
Linolenic acid, an omega-3 fatty acid, has its first double bond at the third carbon from the omega end. Both linoleic and linolenic fatty acids are essential fatty acids. These polyunsaturated fatty acids are needed to sustain life. However, while some fatty acids can be made in the body, these cannot. Both omega-3 and omega-6 fatty acids must be consumed in the diet. 4,5
The daily requirement for linoleic fatty acid is two teaspoons, which is easily met in the American diet. Linoleic acid is found in commercial baked goods, prepared foods, vegetable oils, and margarine. These foods are abundant and are often consumed in large amounts. 3
Omega-3 fatty acids are notably absent from the American diet. Eicosapen taenoic acid (EPA), which is derived from linolenic acid, is the main omega-3 fatty acid in fish. Docosahexaenoic acid (DHA) is yet another omega-3 fatty acid found in fish. Both EPA and DHA are responsible for many impressive health benefits. 4,5
Fatty acids are an important component in cell membranes. The cell membrane surrounds the cell and controls what enters and exits the cell, protecting the cell. When fatty acids are saturated with hydrogen atoms, their chains are rigid and straight. When cell membranes are composed of saturated fatty acid chains, they are closely packed together, creating cell membranes that are rigid and stiff. 4
Polyunsaturated fatty acids have double bonds between carbon atoms. These double bonds allow for a flexible, curved structure. When cell membranes are composed of polyunsaturated fatty acids, they are flexible and elastic. Cell membranes that are flexible are healthier than rigid and stiff cell membranes. 4,5
Human hearts that are made up of cells with rigid membranes are more susceptible to disease. The good news is that hearts comprised of flexible membranes are healthier and less likely to develop heart disease. 5
There has been a vast number of clinical trials and scientific study on the effect of omega-3 fatty acids and heart disease. Impressive results have been noted in lowering the risk of heart attacks and reducing blood pressure.
One recent study examined the blood levels of men who lived in Finland, where fish consumption is fairly high. The men who had the highest levels of DHA and EPA had a 44% reduced risk of acute heart attacks compared to men who had the lowest levels of these omega-3 fatty acids. 6
The effects of dietary fish and weight reduction also were examined in a study of overweight people with high blood pressure (hypertension). The subjects were divided into four groups. One group served as the control and did not receive treatment. The second group ate a daily meal of fish that contained 3.65 grams of omega-3 fatty acids. The third group went on a weight-reduction diet. And, the fourth group combined the meal of daily fish and the weight-reduction diet. Effects on blood pressure were greatest in the combined group. Their blood pressures dropped more than 13 points, much more than the other groups. 7
Another study of blood pressure and omega-3 fatty acids determined supplementation with EPA and DHA was effective in reducing the blood pressure in individuals with hypertension. Blood pressures dropped by six points during supplementation, but returned to baseline after the study was completed. 8
Omega-3 fatty acids also been shown to reduce risk factors that can lead to heart attacks. Two groups of men living in Portugal were compared. One group lived in a farming village and had a low fish intake. The other group was made up of fishermen who normally ate a diet high in fish. The group in the fishing village had lower serum triglyceride levels and total cholesterol levels, both heart attack risk factors. 9
Women who have gone through menopause have a higher risk of heart attacks than other women. It was determined that fish oil supplements lowered serum triglyceride levels and increased high-density cholesterol levels. The study concluded fish oil supplementation reduced the risk of heart attacks by 27% in postmenopausal women. 10
Research has shown fish oil may be beneficial in combatting several diseases. Studies have shown omega-3 fatty acids can reduce the risk of strokes 11, improve asthma in children 12 , relieve depression 13 , and increase the survival time of individuals with cancer. 14-18
In addition, use of fish oil supplements improved nutritional status and increased weight in cancer patients who have lost a significant amount of weight. 19-20 There have also been some impressive results in treating patients with systemic lupus erythematosus 21 , rheumatoid arthritis 22 , and multiple sclerosis. 23
Not all species of fish have high levels of DHA and EPA. Anchovies, salmon, mackerel, tuna, sardines, and herring are the best sources of these omega-3 fattyacids. 3 To achieve the most benefit from eating fish, choices should be made from this list.
Native Inuit, the peoples that were initially the focus of the studies on fish oil, often consume four to five grams of EPAs daily. This equals one and one-half to three pounds of fish 3 and is much more than many people would care to eat. Thankfully, using a fish oil supplement can provide these beneficial omega-3 fatty acids in an easy-to-take form.
Fish oils may naturally contain DHA and EPA, or they may be modified to artificially boost the concentration of DHA and EPA. Recent Norwegian studies have demonstrated that modified fish oils are the least stable and most likely to become rancid. 24,25
An unstable fish oil can actually cause an increase in free radical formation in the blood and tissues. Free radicals can contribute to less flexible blood vessels that may occur with aging or disease. Additionally, the overprocessing of fish oil supplements can result in a loss of key nutrients and thus decrease their effectiveness. 24-26
Purity in fish oil supplements is very important. Fish oil supplement manufacturers should be able to provide documentation of contaminant levels in their products. Supplements should contain no detectable dioxin (a widely used toxic preservative), DDT (a toxic insecticide), PCB (polychlorinated biphenyls), or heavy metals such as mercury and lead.
Choose a fish oil that's not artificially modified to boost the concentration of DHA and EPA and that has added natural antioxidants, including vitamin E, to pre-vent rancidity and provide superior taste and efficacy. 27 Refrigerating the container after opening is often recommended.
Fish oil supplements are a rich source of the polyunsaturated omega-3 fatty acids, EPA and DHA. These fatty acids lower blood pressure, and reduce the risk of heart attacks and strokes. In addition, EPA and DHA may benefit individuals with asthma, multiple sclerosis, systemic lupus erythematosus, and cancer. Fish oil supplements provide a natural yet powerful choice in personal health improvement.
1. Kromhout D, Bosschieter EB, de Lezenne Coulander C., et al. The inverse relation between fish consumption
and 20-year mortality from coronary heart disease. N Engl J Med. 1985 May 9; 312( 19): 1205-9.
2. Kromann N, Green A. Epidemiological studies in the Upernavik district, Greenland. Incidence of some chronic diseases 1950-1974. Acta Med Scand. 1980; 208( 5): 401-6.
3. Pleuss J. Fats. In: Porth CM. Pathophysiology: Concepts of Altered Health States. 5th ed. Philadelphia, Pa: Lippincott; 1998: 1249.
4. Galperin C, German BJ, Gershwin ME. Omega fatty acids. In: Shils ME, Olson JA, Shine M, Ross AC, Eds. Modern Nutrition in Health and Disease. 9th ed. Baltimore, Md: Lippincott Williams & Wilkins; 1999: 1346-1347.
5. Fats: saturated and unsaturated. In: Grodner M, Anderson SL, DeYoung S. Foundations and Clinical Applications of Nutrition: A Nursing Approach. St. Louis, Mo: Mosby; 2000: 118-122.
6. Rissanen T, Voutilainen S, Nyyssonen K, Lakka TA, Salonen JT. Fish oil-derived fatty acids, docosa-hexaenoic acid and decosapentaenoic acid, and the risk of acute coronary events: the Kuopio ischaemic heart disease risk factor study. Circulation. 2000; 102: 2677-2679.
7. Boa DQ, Mori TA, Burke V, Puddley IB, Beilin LJ. Effects of dietary fish and weight reduction on ambu-latory blood pressure in overweight hypertensives. Hypertension. 1998; 32: 710-717.
8. Prisco D, Paniccia R, Bandinelli B, et al. Effect of medium-term supplementation with a moderate dose of n-3 polyunsaturated fatty acids on blood pressure in mild hypertensive patients. Thromb Res. 1998; 91: 105-112.
9. Torres IC, Mira L, Ornelas CP, Melim A. Study of the effects of dietary fish intake on serum lipids and lipoproteins in two populations with different dietary habits. Br J Nutr. 2000; 83: 371-379.
10. Stark KD, Park EJ, Maines VA, Holub BJ. Effect of a fish-oil concentrate on serum lipids in postmeno-pausal women receiving and not receiving hormone replacement therapy in a placebo-controlled, double-blind trial. Am J Clin Nutr. 2000; 72: 389-394.
11. Iso H, Rexrode KM, Stampfer MJ, et al. Intake of fish and omega-3 fatty acids and risk of stroke in women. JAMA. 2001; 285: 304-312.
12. Nagakura T, Matsuda S, Shichijyo H, Hata K. Dietary supplementation with fish oil rich in omega-3 polyunsaturated fatty acids in children with bronchial asthma. Eur Respir J. 2000; 16: 861-865.
13. Mischoulon D, Fava M. Docosahexanoic acid and omega-3 fatty acids in depression. Psychiatr Clin North Am. 2000; 23: 785-794.
14. Bondreau MD, Sohn KH, Rhee SH, Hunt JD, Hwang DH. Suppression of tumor cell growth both in nude mice and in culture by n-3 polyunsaturated fatty acids: mediation through cyclooxygenase-independent pathways. Cancer Res. 2001; 61: 1386-1391.
15. Chen ZY, Istfan NW. Docosahexaenoic acid is a potent inducer of apoptosis in HT-29 colon cancer cells. Prostaglandins Leukot Essent Fatty Acids. 2000; 63: 301-308.
16. Kontogiannea M, Gupta A, Ntanios F, Graham T, Jones P, Meterissian S. Omega-3 fatty acids decrease endothelial adhesion of human colorectal carcinoma cells. J Surg Res. 2000; 92: 201-205.
17. Gramaglia A, Loi GF, Mongioj V, Baranzio GF. Increased survival in brain metastatic patients treated with stereotactic radiotherapy, omega three fatty acids and bioflavonoids. Anticancer Res. 1999; 19: 5583-5586.
18. Gogos CA, Ginopoulos P, Salsa B, Apostolidou E, Zoumbos NC, Kalfarentzos F. Dietary omega-3 polyun-saturated fatty acids plus vitamin E restore immunodeficiency and prolong survival for severely ill patients with generalized malignancy: a randomized control trial. Cancer. 1998; 82: 395-402.
19. Wigmore SJ, Barber MD, Ross JA, Tisdale MJ, Fearon KC. Effect of oral eicosapentaenoic acid on weight loss in patients with pancreatic cancer. Nutr Cancer. 2000; 36: 177-184.
20. Barber MD, McMillan DC, Preston T, Ross JA, Fearon KC. Metabolic response to feeding in weight-losing pancreatic cancer patients and its modulation by a fish-oil enriched nutritional supplement. Clin Sci. 2000; 98: 389-399.
21. Das UN. Beneficial effect of eicosapentaenoic and docosahexaenoic acids in the management of systemic lupus erythematosus and its relationship to the cytokine network. Prostaglandins Leukot Essent Fatty Acids. 1994; 51: 207-213.
22. Volker D, Fitzgerald P, Major G, Garg M. Efficacy of fish oil concentrate in the treatment of rheumatoid arthritis. J Rheumatol. 2000; 27: 2343-2346.
23. Nordvik I, Myhr KM, Nyland H, Bjerve KS. Effect of dietary advice and n-3 supplementation in newly diagnosed MS patients. Acta Neurol Scand. 2000; 102: 143-149.
24. Appleton J, Ackerson A. Health Benefits of a Natural Stable fish Oil. Adv Stand. 1998; 1: 1-2.
25. Saldeen T, Wallin R, Marklinder I. Effects of a Small Dose of Stable Fish Oil Substituted for Margarine in Bread on Plasma Phospholipid Fatty Acids and Serum Triglycerides. Nutr Res. 1998; 18: 1483-1492.
26. Haglund 0, Luostarinen R, Wallin R, SaIdeen T. Effects of fish oil on triglycerides, cholesterol, lipoprotein (a), atherogenic index and fibrinogen. Influence of degree of purification of the oil. Nutr Res. 1992; 12: 455-468.
27. VanGoethem B. Enzymatic Therapy Quality Assurance Department. Providing Information from Cardinova. Stability Studies of Cardinova's Fish Oil Products. March 23, 2001.
- Follow This Discussion by: