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Omega-3 Fatty Acids and Bleeding--Cause for Concern?

Omega-3 Fatty Acids and Bleeding--Cause for Concern?

Article by Arnie Gitomer

Omega-3 Fatty Acids and Bleeding--Cause for Concern?

On February 24th, Dr. Douglas (Duffy) MacKay was our guest on The Willner Window radioprogram. Dr. Mackay, a Naturopathic Physician, is a consultant to Nordic Naturals, one of theleading Fish Oil and Omega-3 oil supplement lines. (

This was the second time Dr. MacKay appeared on the Willner Window, and each visit resultedin one of our more informative and interesting programs. If you would like to hear mp3recordings of the shows, just go to the Willner Chemists web site ( and followeither the "Radio" or "Reference Library" links. Once there, go to the "Radio MP3" section, andselect December 2, 2008 and/or February 24, 2008.

During the latter show, Dr. MacKay surprised us by pointing out that the often repeated concernthat taking fish oil, or omega-3 supplements might cause a problem with excessive bleeding,especially for those people taking antiplatelet or antithrombotic medication is not founded in fact.And he provided a published study, in the American Journal of Cardiology, to support his claim.

I was, of course, more than pleased to hear this, as I have always felt that the concern was way overblown, and not at all supported by observation. Certain factions in medicine and dietetics are very quick to embrace anything that might seem negative about nutritional supplements. Their problem is that there are not many negatives. So this warning about the interaction between fish oil supplements and "blood thinning" medication, so often repeated, has come to be taken as fact.

According to Dr. MacKay, however, it is not fact. It is, instead, a myth. Here is what Dr. MacKay says: "Experts are confident that omega-3 fatty acids in doses of 1 - 4 grams per day (and even greater doses) DO NOT increase the risk of clinically significant bleeding, even in patients also being treated with antiplatelet or antithrombotic medication.

"This is based on a recent published review of 2 studies in which patients underwent coronar yartery bypass grafting, 2 trials of carotid endarterectomy, and 15 trials in patients who underwent femoral artery catheterization. Various doses of fish oils were used and in several cases concomitant use of blood-thinning medication."

The published review he is referencing was the American Journal of Cardiology2007;99[suppl]44C-46C.

The title of the paper was "Expert Opinion: Omega-3 Fatty Acids and Bleeding--Cause for Concern?" by William S. Harris, PhD. (Sanford School of Medicine of the University of South Dakota)

The summary, or abstract, or Dr. Harris' paper is as follows:

"Omega-3 fatty acid ethyl esters have well-known triglyceride-lowering properties and were shown >30 years ago to inhibit platelet function. With the recent US Food and Drug Administration (FDA) approval of these agents for treating severe triglyceride elevations,concerns about excess bleeding naturally arise. However, an objective assessment of the evidence for clinically significant bleeding reveals that such concerns are unfounded. As such, the benefits of triglyceride lowering with omega-3 fatty acids more than outweigh any theoretical risks for increased bleeding."

The final sentence, above, is what is most significant. Everything--every medication, every supplement, every lifestyle modification--has an upside, and a downside, a pro and an con. We need, in each case, to weight the benefits against the risks.

Omega-3 oils are healthy. They are, in fact, so healthy that they are potentially therapeutic. They redice triglycerides. They reduce inflammation. Both of these functions are of primary benefit to people with cardiovascular disease. Does it really make sense to avoid their use merely because of the theoretical possibility of excess bleeding when combined with other blood thinning medication?

As I have said many times, if those who are so quick to warn against their use are convinced that omega-3 oils are indeed that potent, maybe they should prescribe the fish oil, and warn against the medication, instead of vice versa.

According to the Am J Cardiol study, "As the health benefits of omega-3 fatty acids become clearer, interest in defining the potential adverse effects of these nutrients naturally increases. In the review by Bays1 in this supplement, the possibility of increased risk for bleeding with omega-3 fatty acids is addressed. Bays clearly describes the role of omega-3 fatty acids in eicosanoid metabolism, which forms the biochemical basis for the concern for increased bleeding with omega-3 fatty acids. He concludes that although there is little evidence for increased risk for clinically significant bleeding with omega-3 fatty acid supplementation, clinicians should be mindful of this as a theoretical possibility."

Dr. Harris goes on to elaborate, as follows. "The relevant clinical question is the following: What is the evidence that taking long-chain omega-3 fatty acids in doses of 1-4 g/day causes clinically significant bleeding? To answer that question, studies were examined in which these doses (and typically even greater doses) were provided to patients who underwent major vascular surgery(coronary artery bypass grafting or endarterectomy) or femoral artery puncture for either diagnostic cardiac catheterization or percutaneous transluminal coronary angioplasty."

The studies were analyzed, and summarized, and Dr. Harris found that ". . .the risk for clinically significant bleeding was virtually nonexistent."

In addition, Dr. Harris point out the following: "Several years ago, Knapp21 reviewed the published research regarding omega-3 fatty acids and human thrombosis and hemostasis. In addition to noting the lack of significant bleeding with omega-3 fatty acid supplementation in cardiovascular studies to date, he also referred to studies in pregnant women in which supplementation with omega-3 fatty acids 2.7 g/day did not lead to increased blood loss at delivery,22 and he noted that supplemented dialysis patients were not at increased risk for bleeding.23,24 There had been 1 report that fish oil (5 g) caused increased risk for nosebleeds in children with hypercholesterolemia,25 but this could not be replicated in a later trial in children on dialysis.26

"Thus, the experience has been virtually unanimous: omega- 3 fatty acid supplements do not increase the risk for clinically significant bleeding, even in patients also being treated with antiplatelet or antithrombotic medications. . ."

Yes, this may not be the final word. And yes, we do not have similar research on newer anti-platelet drugs. But, according to Dr. Harris, "Given our present knowledge, I would agree with Bays1 that we are "confident" that omega-3 fatty acids do not increase risk for adverse bleeding episodes."

More studies, and ongoing studies, are needed, of course. "Nevertheless, in considering the risks and benefits of omega-3 fatty acids for cardiovascular risk reduction, the latter continue to outweigh the former."

So, the next time you are warned against omega-3 supplements, direct that person to American Journal of Cardiology 2007;99[suppl]: pages 44C-46C)

by Don Goldberg