Fish Oil Reduces
Atherosclerotic Blockages

This section is compiled by Frank M. Painter, D.C.
Send all comments or additions to:    Frankp@chiro.org

From The October 1999 Issue of Nutrition Science News

By Richard N. Podell, M.D.

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Evidence that a diet rich in fish reduces the incidence of heart disease [1,2] is so strong and the news so widespread that people are taking it for granted. Despite the promising evidence of this preventive effect, however, remarkably few human studies prove encapsulated fish oil is more effective than placebo as a heart disease treatment. The few studies were relatively small and had mixed results—some showing benefit, others not. [3-6]

Hence, research published recently in The Annals of Internal Medicine, a prestigious U.S. medical journal, is important because the two-year study shows fish oil may be a means of slowing or reversing atherosclerotic heart disease.

German researcher Clemons von Schacky, M.D., and colleagues from the University of Munich studied 223 patients with significant blockages (atherosclerosis) in their heart arteries. Blockages were detected by an X-ray technique called coronary arteriography, where dye is squirted into the coronary arteries through a catheter placed at the main opening of these vessels.

All the patients received their usual medicines. In addition, half took 6 g of omega-3 fish oil capsules (55 percent eicosapentaenoic and docosahexaenoic acids) daily for three months, then 3 g daily for the next 21 months. The other half received placebo containing a nonomega-3 unsaturated oil. After two years, the coronary arteriogram was repeated on 160 patients, about 80 in each group. The pairs of arteriogram films were analyzed and scored by three cardiologists who didn't know which patients were taking fish oil or which arteriograms were done before or after supplementation.

Of the 51 patients in the placebo group who showed significant changes on their second arteriograms, 44 showed mild or moderate progression of atherosclerosis and seven showed mild regression. In contrast, among the 59 patients taking fish oil who showed changes, 36 showed mild progression but 19 showed some form of regression—17 had a mild degree and two a moderate degree of improvement. The difference in favor of fish oil was statistically significant. [7]

Few patients developed new cardiovascular events such as heart attack or stroke during the two-year study. However, among those who did, there was indication of a protective effect from fish oil. Seven patients taking placebo, but only two taking fish oil, developed significant cardiovascular events. The probability of this difference occurring by chance was one in 10. Though not quite statistically significant—one chance in 20 is the cutoff—this difference is encouraging given the very small number of incidents. No side effects were attributed to either fish oil or placebo.

The modest overall advantage fish oil provided in this study was impressive. That any difference at all was detected, given the relatively small number of patients during the two-year treatment, is notable. Researchers concluded that supplementation with fish oil "modestly mitigated the course of human coronary atherosclerosis."

Most likely, fish oil reduces atherosclerosis by thinning blood, which makes the tiny blood platelets less likely to clot. Previous studies show that omega-3 oils affect certain genes within cell nuclei. These genes create proteins that influence the stickiness of blood platelets. [8]

Other research shows high doses of fish oil to be moderately effective for treating rheumatoid arthritis [9] and very effective for preventing relapses of Crohn's disease—a chronic inflammatory disease of the gastrointestinal tract. [10] One study found fish oil supplementation doubled survival time among people who had advanced cancer of the breast, colon, lung or pancreas. [11]

As evidence for the potential efficacy of fish oil supplements mounts, the need for further research will certainly become a higher scientific priority.

Sidebars:

Fish Oil Performs Swimmingly

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Richard N. Podell, M.D., M.P.H., is director of the Podell Medical Center in New Providence, N.J.

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References

1. Shekelle RB, et al. Diet, serum cholesterol, and death from coronary heart disease. The Western Electric Study. N Engl J Med 1981;304:65.

2. Kromhout D, et al. The inverse relation between fish consumption and twenty year mortality from coronary heart disease. N Engl J Med 1985;312:1205.

3. Burr NM, et al. Effects of changes in fat, fish and fiber intake on death and myocardial reinfarction, diet and reinfarction trial (DART). Lancet 1989;334:757-61.

4. Gapinski J. Preventing restenosis with fish oils following coronary angioplasty. Arch Intern Med 1993;153:1595-1601.

5. Eritsland J. Effect of dietary supplementation with omega-3 fatty acids on coronary artery bypass graft patency. Am J Cardiol 1996;77:31-6.

6. Sacks F, et al. Controlled trial of fish oil for regression of human coronary atherosclerosis. HARP Research Group. J Am Coll Cardiol 1995;25:1492-8.

7. von Schacky C, et al. The effect of dietary omega-3 fatty acids on coronary atherosclerosis. Ann Intern Med 1999 Apr 6;130(7):554-62.

8. Fox P, DiCorieto P. Fish oils inhibit endothelial cell production of platelet derived growth factor-like protein. Science 1988;241:453-6.

9. Kremer J. Effects of high-dose fish oil on rheumatoid arthritis after stopping nonsteroidal anti-inflammatory drugs. Arthritis Rheum 1995;38:1107-14.

10. Belluzzi A. Effect of an enteric-coated fish-oil preparation relapses in Crohn's disease. N Engl J Med 1996;334:1557-60.

11. Gogos C, et al. Dietary omega-3 polyunsaturated 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

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