Millions Take These Dietary Supplements — but They May Raise Heart Risk

Fish oil supplements are often taken with the belief that they are a simple shortcut to better heart health. They are sold as a convenient source of omega-3 fatty acids, and many people use them because they have heard that eating oily fish is good for the heart.

But the warning is more complicated than the label suggests. A large BMJ Medicine study using UK Biobank data found that regular fish oil supplement use was associated with a higher risk of atrial fibrillation and stroke among people without known cardiovascular disease, while the pattern looked different among people who already had heart disease. The study was observational, so it shows an association, not proof of cause.