SANTA MARIA IMBARO, ITALY. A group of Italian researchers (GISSI) reported in 1999 that supplementation with fish oils reduces the mortality among patients who have survived a first heart attack. Their study involved over 11,000 heart attack survivors who supplemented with 1 gram/day of fish oil (580 mg of eicosapentaenoic acid [EPA] and 290 mg of docosahexaenoic acid [DHA]) for 3.5 years.
The researchers have now re-analyzed their data in an attempt to determine how the fish oil exerts its protective effect. The reduced mortality was apparent after only three months of supplementation (1.1 per cent versus 1.6 per cent in the placebo group) and continued for the duration of the study. The reduction in the incidence of sudden cardiac death accounted for about 57 per cent of the total improvement in mortality rates. At the end of the study 2.7 per cent of the placebo group participants had died from sudden cardiac death as compared to only 2.0 per cent in the fish oil group. Overall, cardiovascular death (including stroke) at the end of the study was 6.5 per cent in the placebo group versus 5.5 per cent in the fish oil group. There was no statistical significant difference in the incidence of non-fatal heart attacks between the fish oil and placebo groups.
The researchers conclude that fish oils exert their protective effect by preventing fatal ventricular arrhythmias rather than through an improvement in cholesterol profile. They did note a small (4.6 per cent) drop in triglyceride levels in the fish oil group, but found no significant differences in LDL (low-density lipoprotein) and HDL (high-density lipoprotein) cholesterol between the two groups. They also point out that the number of lives (per 1000 patients) which could be saved every year by giving heart attack survivors fish oil exceeds the number of lives (per 1000 patients) estimated to be saved by treating heart disease patients with high cholesterol levels with pravastatin. This puts fish oils squarely in the category of highly effective heart "drugs".
Marchioli, Roberto, et al. Efficacy of n-3 polyunsaturated fatty acids after myocardial infarction: results of GISSI-Prevenzione trial. Lipids, Vol. 36, Supplement 2001, pp. S119-S126
Marchioli, Roberto, et al. Early protection against sudden death by n-3 polyunsaturated fatty acids after myocardial infarction: time-course analysis of the results of GISSI-Prevenzione. Circulation, Vol. 105, April 23, 2002, pp. 1897-1903
Leaf, Alexander. On the reanalysis of the GISSI-Prevenzione. Circulation, Vol. 105, April 23, 2002, pp. 1874-75 (editorial)