Do Fish Oil Capsules Prevent Heart Disease?

Sometimes, good ideas just don’t turn out as we expect. This Interesting-Article-of-the-Week is one such case and is, perhaps, the death knell for fish oil capsules so long prescribed for heart disease.Capsule

It has long been noted that those societies that eat lots of fish tend to have less heart disease and live longer and healthier lives than we Americans. One great example is the Mediterranean diet that has recently been in the news . So what is it about eating fish that leads to such good results? One theory was that it was the good fats found in fish that produce the benefits, particularly omega-3 fatty acids. It had been shown that eating omega-3 fatty acids reduced high triglyceride numbers, and high triglycerides were associated with heart disease, so it makes sense that lowering the triglycerides would reduce heart disease. Right? So the idea was: let’s put those omega-3 fatty acids into a convenient capsule so people can get the benefits without having to actually eat fish.

Omega-3 fish oil capsules have come to be quite commonly prescribed. They are, in fact, recommended as a heart disease preventative by several professional organizations. But the tide is turning. There have been several articles published in the last several years questioning the effectiveness of fish oil . This article is the latest and most important.

Association between omega-3 fatty acid supplementation and risk of major cardiovascular disease events: a systematic review and meta-analysis. JAMA. 2012 Sep 12;308(10):1024-33.

This article is a meta-analysis of 20 randomized trials involving of fish oil supplementation involving 68,680 patients performed between 1989 and 2012. Unfortunately, its conclusion is that taking the omega-3 supplements appears to have no effect on cardiovascular mortality, all-cause mortality, sudden death, myocardial infarctions, or stroke. This includes the highest risk patients as well. For example, those patients who had implantable defibrillators also had no discernible benefit from omega-3s.

How can this be? People with elevated triglyceride levels have an increased risk of heart disease. And fish oil supplementation does lower these triglyceride levels. How could it possible not affect cardiovascular events?

The answer is that the fact that people with elevated triglyceride levels have an increased risk of heart disease is a correlation rather than a causation.

20060412A great analogous example is this: you would find, if you were to study it, that people who have many ashtrays in their homes have an increased risk of having heart disease. However, if you were to remove all of their ashtrays, their incidence of heart disease would not change—because the ashtrays were not causing the heart disease. Instead, of course, smoking is the culprit that causes the heart disease–and smokers tend to have ashtrays in their homes. Thus, ashtrays are correlated with heart disease, but do not cause heart disease.

Elevated triglycerides appear to be similar to this. Fish oil supplementation will reduce elevated triglyceride numbers, and are still a legitimate therapy for those patients who have triglyceride levels of greater than 500. Fish oil capsules may have other positive effects, as well. Some of my CrossFit friends swear by them as being a “natural anti-inflammatory” and preferable to NSAIDS for reducing muscle soreness and aches. That may or may not be true; it has never been studied to my knowledge.

But the effect of fish oil supplementation on heart disease has been studied–extensively. And, as this meta-analysis concludes, fish oil has no effect on cardiovascular disease or mortality.

I still occasionally see patients come to the jail who are prescribed fish oil tablets by their outside practitioner. I usually will let such patients continue to take the fish-oil capsules they brought to the jail with them. But I will not prescribe them myself. So if these patients stay in jail long enough for their outside medications to run out, I then will go over their medication list with them and explain why I am making changes.

Are fish oil capsules still prescribed as a therapy for heart disease in your facility? Please comment!

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10 thoughts on “Do Fish Oil Capsules Prevent Heart Disease?

  1. Dr. LaBash

    The medical director of the facility I just started working at is a proponent of fish oil. He is also somewhat reluctant to prescribe statins because of side effects. He seems well read, so I can’t simply dismiss his viewpoint. I do not intend to start anyone on them, and I’m certainly not going to recommend them instead of statins, but I won’t discontinue them either.

    Reply
    1. Jeffrey Keller MD Post author

      Thanks for the comment, Dr. LaBash. Statins do, indeed, have side effects that are under-appreciated by the majority of prescribers–but let’s not throw out the baby with the bathwater! Statins are (IMO) an appropriate medication in the proper patient–those who have known coronary artery disease. I don’t personally believe in their effectiveness for patients at low risk for CAD–whether their cholesterol numbers are high or not! But that is a good subject for another post!

      Reply
  2. Patty Workman NP

    Haven’t used them in a year or two, since the literature started coming out more and more showing no benefit. (Can’t afford to waste money!)

    Reply
    1. Jeffrey Keller MD Post author

      Thanks for the comment, Patty. The biggest expense is not the cost of the pills, themselves, but the time and energy cost of ordering, receiving, stocking, passing day after day, reordering and on and on.

      Reply
    1. Jeffrey Keller MD Post author

      Thanks for the comment, Than! Vitamin D would be a good subject for a future post.

      Reply
    1. Jeffrey Keller MD Post author

      Thanks for the comment, Mark! Lots of my inmates say they are allergic to fish, as well, especially on the days when tuna casserole is served.

      Reply
  3. Dave M.

    Good points in your article about taking supplements. However I think the bottom line is that actually consuming fish, rather than hoping for a quick and easy fix by popping fish oil pills, is what provides observed benefits to heart health. Factors that may come into play include people taking fish oil capsules but continuing with unhealthy lifestyle choices like lack of exercise and bad diet or smoking. Additionally, there may be some “cofactor” in fatty fish that acts in conjunction with the fish oil to produce lower rates of heart disease seen among fish eaters that is missing in the capsules. Plus, fish generally has less saturated fat than beef – so by eating more fish, Japanese or Inuit may at least partially be deriving benefit by eating fish as opposed to a steak or Big Mac – benefits that could also be achieved with a low fat chicken dinner. In my view its likely fish oil does provide some benefit but the story is more complicated than could be solved with a dietary supplement.

    Reply

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