Harvard Medical School
Question. I’m taking fish oil supplements to keep me from getting heart disease, because my doctor said they may help, though it’s controversial. I hear new studies come to different conclusions. What’s the truth?
Answer. In these pages, the best we can promise you is a balanced assessment of sometimes different study results: the “truth” usually is elusive.
Your question likely was prompted by two important new studies published in November 2018, and they do seem to point in different directions. I’ll do my best to give you my current “bottom line” and resolve the confusion. I reserve the right to change my mind as new studies are reported.
A large (nearly 13,000 people) randomized trial, based here at Harvard Medical School, tested the cardiovascular benefits of one particular formulation of fish oil supplements (which contain high levels of omega-3 fatty acids).
“Cardiovascular benefits” included lower rates of any diseases that result from atherosclerosis, primarily of the arteries of the heart or brain. After following people for an average of more than five years, there was no clear benefit in the total of all cardiovascular problems.
The people receiving fish oil did have lower rates of some types of heart problems, but these results were not as statistically strong as those for the total of all cardiovascular problems. Because this was the largest study of its kind, many doctors who once recommended fish oil supplements to protect against heart disease are no longer doing so.
Yet, I don’t think the question is settled, in part because “fish oil” is not one chemical but a complex mix of chemicals, and different fish oil pills have different mixes of those chemicals. This study tested just one particular mix.
For example, another study based here at Harvard Medical School, and led by Dr. Deepak Bhatt, editor-in-chief of our sister publication, the Harvard Heart Letter, tested one particular component of fish oil, called icosapent ethyl.
This randomized trial of over 8,000 people followed for five years found a 25% reduction in total cardiovascular problems, although people given the supplement also had a 1% higher risk of developing a particular heart rhythm abnormality (atrial fibrillation or flutter). The people in this study, unlike the first study, had one or more risk factors for cardiovascular problems.
So what’s my current bottom line? At least two meals of fish (not fish oil supplements) per week appear to protect people without known heart disease from getting it. On the other hand, most available fish oil supplements don’t clearly do so.
The particular fish oil component called icosapent ethyl may protect against getting heart disease in people with risk factors for heart disease, but its value in people without risk factors is uncertain.
