Fish oil has long been thought to be good for the heart. In many cases it absolutely is excellent at preventing heart attacks because it helps to reduce bad cholesterol, which may lead to plaque in the arteries and a malfunctioning heart. However, evidence gathered in 2005 suggest that at least some people with pre-existing heart problems should not take fish oil, and that it in fact may do more harm than good.

A 2005 study examined patients with previous arrhythmias to evaluate the benefits of a regular regimen of fish oil supplementation. In this study the desired finding was that fish oil would reduce incidence of arrhythmias, and thus would be a great complementary tool to traditional heart medicines and treatment.

In many cases, abnormal heart beat incidences did decrease. However one group, those with ventricular tachycardia, actually had more incidences of arrhythmias than the group taking the placebo. While scientists are not quite certain why this occurs, they are clear that fish oil may pose more risk than benefit to those who have previously suffered a heart attack or who have had ventricular tachycardia diagnosed in the past.

Further studies with a patient population consisting entirely of patients with ventricular tachycardia confirm these results, and now doctors are backtracking on the issue of recommending fish oil to patients with heart problems, particularly when these problems are of tachycardic origin.

Those who have ventricular tachycardia can have very high quick rhythms of the heart, which can cause heart attacks. In some cases, ventricular tachycardia may require placement of a defibrillator to control abnormal rhythms. Even when a person has a defibrillator placed, he or she should probably avoid fish oil.

It is unclear whether fish oil might predispose one who might ultimately develop arrhythmias to get them sooner. Scientists think those with ventricular tachycardia may process oils in a way differently than other people, though this mechanism is not clearly understood.

In most cases a daily dose of fish oil can be a heart healthy choice. However those with arrhythmias or a family history of arrhythmias should definitely discuss their risks with a doctor prior to taking fish oil.