The American Heart Association has recommended the inclusion of more fish in the diet because four trials had shown that eating fish or regularly using a fish oil supplement lowered the risk of sudden cardiac death. However, headlines in recent newspaper articles made me question my habit of taking a daily fish oil capsule and may have shaken your faith in these recommendations.
The worrisome newspaper articles described the results of a controlled trial in 200 patients who were randomized to take either fish oil (1.8 grams daily) or a placebo (olive oil) for an average of about 2 years. All the patients had an implanted defibrillator device programmed to deliver a powerful electric shock because they had previously suffered bouts of a dangerous abnormal heart rhythm, either sustained ventricular tachycardia or ventricular fibrillation. Ventricular tachycardia is an extremely rapid heart rate that can cause the heart to fail if it continues too long. Ventricular fibrillation, a quivering of the ventricle that prevents it from pumping blood, leads to death or brain damage if not stopped with an electric shock within 10 minutes.
The investigators were surprised to find that the patients taking fish oil had recurrent bouts of ventricular tachycardia sooner and more often than those taking the placebo. These bouts were accurately detected through recordings made by the implanted defibrillator.
Do these results mean that omega-3 fatty acids are not beneficial, or are even harmful? Probably not. The patients enrolled in this study did not have prior heart attacks and had already shown they were prone to develop these dangerous disturbances of heart rhythm. Patients who had benefited in the previous studies had recent heart attacks and better heart function. So it still seems likely that omega-3 fatty acids can benefit people with recent heart attacks and possibly people in the general population. And fish oil supplements certainly can lower blood triglyceride levels. People with an implanted defibrillator would be wise to avoid fish oil supplements.