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Fish Oil – Better Left in the Fish?
Everybody knows fish oil is good for you. It’s one of the most popular diet supplements, and even the FDA allows claims that it can help prevent heart attacks. It has been claimed to help everything from schizophrenia to psoriasis. Here are the only claims that are supported by good quality evidence:
1. In patients who have had a heart attack, fish oil improves survival.
2. It reduces triglycerides.
3. In patients with high cholesterol levels it reduces the risk of coronary events but does not decrease mortality.
4. It reduces blood pressure slightly.
There are some concerns. In the DART 2 trial of men with chronic coronary disease (stable angina), it apparently increased the risk of death. In a study of patients who had an implanted cardioverter defibrillator, it increased the risk of arrhythmias. With higher doses, it can worsen control of diabetes and it can increase bleeding tendency. Side effects include burping, heartburn, and an unpleasant aftertaste.
People see that fish oil improves survival after a heart attack so they assume it should also help prevent heart disease in people who don’t yet have it. That does not necessarily follow: insulin improves survival of diabetics, but that doesn’t mean healthy people should take insulin to prevent diabetes.
A 2006 review article in The Medical Letter concluded, “Eating fatty fish may be beneficial for healthy people, but there is no evidence from prospective trials that fish oil supplements prevent cardiovascular disease in the general population.”