By: Steven Nissen, MD
Cleveland Clinic is a non-profit academic medical center. Advertising on our site helps support our mission. We do not endorse non-Cleveland Clinic products or services. Policy
The American Heart Association (AHA) has issued an updated set of recommendations for people who have had a heart attack or who suffer from heart failure.
According to the AHA, these heart patients should add a fish oil supplement to their diet to help prevent future heart-related events. Fish oil contains omega-3 fatty acids, which, when consumed by eating fatty fish, can cause blood vessel relaxation, reduced blood clotting, reduced inflammation and possibly stabilization of heart rhythm.
But I disagree with the AHA’s updated recommendation. Here’s why.
1. The studies on fish oil supplements are conflicting
When it comes to the science behind fish oil or omega-3 supplements, the results are varied and oftentimes are conflicting. More research needs to be done before confirming that adding a fish oil supplement will help reduce a person’s risk of future heart-related events.
Only one large, randomized controlled clinical trial — the gold standard in scientific research — supports the concept that daily administration of 1 gram of an EPA/DHA fish oil combination may benefit patients with coronary heart disease who have suffered a heart attack. Some scientists, however, take issue with the design and conduct of this and other studies that suggest a benefit from fish oil supplements in heart patients.
There also are studies with heart patients that have failed to confirm the benefits of the omega-3s. While some of these studies also have potential flaws that could explain their results, they do open the door to reasonable doubt.
We also don’t know for certain whether fish oil supplements are harmful — again because we have no strong evidence to support or dispute that statement.
So when we have that kind of a mixed picture, the right thing to do is to ask for more research to resolve this conflict — not tell people to take something because there might be some benefit.
2. The supplements are not proven safe and effective
Like all nutritional supplements, fish oil supplements are not regulated by the Food and Drug Administration (FDA), and do not go through the rigorous process of proving that they are safe and effective. Instead, supplements are regulated by Federal Trade Commission (FTC), which has no scientific expertise and does not even confirm whether the supplements actually contain the ingredients listed on their labels.
When you take over-the-counter fish oil, you don’t know what you’re taking. The supplement may or may not contain the amount of fish oil that it is alleged to contain, and so we don’t recommend that people take dietary supplements — particularly when there is no solid evidence of a benefit.
3. Fish oil supplements can have side effects and contain contaminants
Fish oil has a mild blood-thinning effect and supplements should not be taken by patients who are taking blood thinners or who have propensity for bleeding. The supplements also can cause indigestion and fishy burps.
Some fish oils may be contaminated with mercury. Research has shown that a large proportion of supplements — perhaps as much as 40 percent — contain contaminants, including lead, bacteria and pesticides.
Eat fish, not pills
For people thinking about taking fish oil supplements, my advice is to talk with your doctor first.
I personally would not recommend that you put anything in your body without very good evidence of benefit. If you want to get more fish oil in your diet, you are better off simply eating more fish.
Oily fish belongs your diet — particularly as a replacement for red meats. Walk past the red meat counter at the grocery store every week and go instead to the seafood counter and get a nice piece of salmon. You reap a double benefit: a reduced intake of unhealthy saturated fats from red meat and ingestion of (potentially) heart-healthy fish oils.
If you don’t like fish, you can get plant-based omega-3 fatty acids from flaxseed, walnuts, green vegetables and some vegetable oils, including canola oil. Incorporating these foods into your diet is relatively easy: Sprinkle ground flaxseed on your cereal or yogurt, eat a handful of walnuts as a snack instead of a candy bar, or make a salad dressing with flaxseed oil.
The evidence, however, that plant-based omega-3 fatty acids are heart-healthy is substantially weaker than the evidence in favor of fish-based omega-3s. For that reason, fish is the best choice.