How Does Fish Oil Affect Heart Health?

How Does Fish Oil Affect Heart Health?

Healthnotes Newswire (June 30, 2005)—While a large body of research has shown that eating fish or taking fish oil supplements can reduce the risk of heart disease–related deaths in the general population, for people with a history of certain serious arrhythmias they may actually increase the risk of recurrence, reports a study in the Journal of the American Medical Association (2005;293:2884–91). The results of this study suggest that people with a history of sustained ventricular tachycardia or ventricular fibrillation should not take fish oil supplements.

A normal heart maintains a regular pumping rhythm by means of an internal electrical system that sends signals to the heart muscle cells. This signaling mechanism can go awry for many different reasons, leading to abnormalities of the heart rhythm that range from merely uncomfortable to life threatening. Two of the most serious arrhythmias—sustained ventricular tachycardia and ventricular fibrillation—may cause the heart to stop beating, resulting in sudden death. In order to reduce the risk of sudden death in people who experience these arrhythmias, doctors may implant a device in the body (an implantable cardioverter defibrillator; ICD) that automatically shocks the heart into pumping again when it detects a dangerous arrhythmia. Because fish oil has been shown to prevent arrhythmias and sudden death in previous studies, researchers investigated whether it might also help people who have the most serious types of arrhythmia.

Two hundred people who had received an ICD because of a previous episode of sustained ventricular tachycardia or ventricular fibrillation were randomly assigned to receive 1.8 grams of fish oil per day or a placebo (olive oil) for two years. A memory device contained in each ICD recorded the number of times the machine was triggered during the study to shock the heart. The effect of the treatment was evaluated after 6, 12, and 24 months of supplementation. At each of these time points, the proportion of participants in whom the ICD had been activated was higher in the fish oil group than in the placebo group, although the difference between groups was not statistically significant. When considering only those people whose initial problem had been ventricular tachycardia (about two-thirds of all of the participants), the adverse effect of fish oil relative to placebo was statistically significant.

The researchers considered the possibility that their findings could be explained by a beneficial effect of the olive oil placebo, as opposed to a negative effect of fish oil. However, while olive oil does have some beneficial effects on the heart, animal studies have not shown any effect on arrhythmias.

The results of this study suggest that people who have had sustained ventricular tachycardia or ventricular fibrillation should not take fish oil supplements. The findings may not apply, however, to people who have had these arrhythmias as a direct result of a heart attack, or to people with reversible causes of these arrhythmias; people with those types of sustained ventricular tachycardia or ventricular fibrillation were not invited to participate in the study. It should be stressed again that for those without a history of the arrhythmias studied, fish oil has been reliably demonstrated to be a safe and heart-healthy supplement.

An expert in nutritional therapies, Chief Medical Editor Alan R. Gaby is a former professor at Bastyr University of Natural Health Sciences, where he served as the Endowed Professor of Nutrition. He is past-president of the American Holistic Medical Association and gave expert testimony to the White House Commission on Complementary and Alternative Medicine on the cost-effectiveness of nutritional supplements. Dr. Gaby has conducted nutritional seminars for physicians and has collected over 30,000 scientific papers related to the field of nutritional and natural medicine. In addition to editing and contributing to The Natural Pharmacy (Three Rivers Press, 1999), and the A–Z Guide to Drug-Herb-Vitamin Interactions (Three Rivers Press, 1999), Dr. Gaby has authored Preventing and Reversing Osteoporosis (Prima Lifestyles, 1995) and B6: The Natural Healer (Keats, 1987) and coauthored The Patient's Book of Natural Healing (Prima, 1999).

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