For many years, I suggested that my cardiology patients take fish oil supplements as an easy way of getting heart-healthy omega 3 fatty acids.

I'm rethinking that advice. Here's why.

About one in five American adults takes fish oil capsules, often because they have been told it can help prevent a heart attack or even treat coronary artery disease.  People also take it for other reasons, such as arthritis and depression.  Eating enough fish is hard to do, so my advice has always been to take the pill and get the same benefits.

But science has me doubting this wisdom. Two recent studies, both of which examine all of the available data about the effects of fish oil – and there are a lot — suggest there is no advantage, except possibly to the makers of the pills.

One study, published in the heart journal Circulation, reinforces the idea that fish oil, when taken by people without heart disease, did not change the risk of having a heart attack, stroke or heart failure.

The second study, in JAMA Cardiology, went even further.  Published earlier this year,  this meta-analysis (a review of all large fish oil trials done to date) showed no payback of any kind in preventing heart attacks, strokes, or heart-disease-related death in the more than 77,000 high-cardiac-risk individuals who participated in 10 large clinical trials.

There is no doubt that eating actual fish once or twice a week, especially the "oily" kinds of fish rich in omega 3 fatty acids called DHA and EPA, is associated with a lower risk of dying from a heart problem. Fried fish, alas, does not count, because deep-frying anything poses its own health risks.

So how did so many cardiologists and patients fall for fish oil supplements?

Early fish oil studies strongly suggested a cardiac benefit of supplements.  For example, the GISSI-Prevenzione Trial showed a 10 percent reduced risk of having a heart attack in patients who took omega 3 fatty acid capsules, compared with a group of people who did not.  But, the results of recent, larger and better-designed trials have been more equivocal.

Bottom line: Without evidence that they prevent heart attacks in those with no history of heart disease, or prevent further problems in high-risk individuals, it is hard to support the routine use of this supplement.

If you have both high triglyceride levels and heart disease, these supplements will lower triglyceride levels. Though it's not proven that doing so will extend life, for these people the supplements might make sense.

In view of all this, here are my recommendations:

  1. There are several prescription fish oils.  Some are now generic, have the advantage of being approved by the U.S. Food and Drug Administration, are rich in DHA and EPA, and are purified.  They are often not covered by many prescription plans and can be expensive. If you are going to continue fish oil supplementation, this is the ideal kind to take.
  2. Over-the-counter fish oils are not regulated by the FDA and may not be filtered for heavy metals such as mercury.
  3. Studies are ongoing to see whether high-risk patients with high triglycerides and low HDL (good) cholesterol will live longer if they take omega 3 fatty acids.
  4. If you do not have a heart problem, and are taking fish oil to prevent one, I would suggest stopping it.
  5. If you have had a heart attack or other heart problem, are on other medications such as statins that decrease future risk, have normal triglyceride levels, and are taking a fish oil supplement, there is no proof that it helps, but is possible that it has a small effect.
  6. It is a popular misconception that taking fish oil will help lower your cholesterol. It will not, but instead can actually raise your LDL (bad) cholesterol levels.
  7. Side effects from omega 3 fatty acids can include burping up a fishy taste, stomach distress, and heartburn.

Most of us probably do not need these supplements, and the side effects and cost likely outweigh any advantages.  As I have believed strongly in the beneficial effects of omega 3 fatty acid for many years, I find this to be a painful conclusion. But in medicine, it is important to follow the evidence, and right now the sum of all these trials suggests that this popular item should be left on the shelf.

David Becker, M.D., is a frequent Inquirer contributor and a board-certified cardiologist with Chestnut Hill Temple Cardiology in Flourtown, Pa. He has been in practice for 25 years.