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NLM Director’s Comments Transcript
Fish Oil May Not Prevent Heart Attack, Stroke: 10/22/2012

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Greetings from the National Library of Medicine and

Regards to all our listeners!

I'm Rob Logan, Ph.D. senior staff National Library of Medicine for Donald Lindberg, M.D, the Director of the U.S. National Library of Medicine.

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Fish oil consumption may not prevent heart attacks, stroke, or death, suggests a systematic review recently published in the Journal of the American Medical Association.

The review of 20 international clinical trials (with about 69,000 patient participants) found no significant associations among omega-3 fatty acid (or fish oil) and the prevention of: heart attacks, stroke, mortality from all causes, heart-related deaths, and sudden deaths.

The study’s authors, who are researchers and physicians from Greece, carefully selected randomized clinical trials that assessed fish oil’s clinical efficacy. The clinical trials from nations such as the U.S., Italy, France, the Netherlands, Norway and the UK, occurred between 1989-2012 and each followed trial participants for at least one year. Interestingly, five of the selected trials were funded by the food supplement industry.

In most of the trials, the studies compared participants who did and did not take fish oil supplements. In two of the trials, participants received differing counseling to increase omega-3 rich foods in their diets.

Among the systematic review’s interesting findings, omega-3 fatty acids did not have a preventive impact regardless if trial participants took supplements or ate omega-3 rich foods, such as salmon and sardines.

The authors acknowledge nutritionists once hypothesized a diet high in omega-3 fatty acids might help prevent heart attacks and stroke. However, the authors explain the current study joins recent research that suggests fish oil’s preventive influence may be less than anticipated.

The authors conclude (and we quote): ‘omega-3 polyunsaturated fatty acids are not statistically significantly associated with major cardiovascular outcomes across various patient populations. Our findings do not justify the use of omega-3 as a structured intervention in everyday clinical practice or guidelines supporting dietary polyunsaturated fatty acid administration’ (end of quote).

Although the systematic review provides the most comprehensive evidence about the associations among omega-3s, heart attack and stroke prevention to date, the authors note future clinical trials should address additional questions that could challenge current findings. For example, the authors suggest future trials assess the extent patients adhere to taking omega-3 supplements or increase fish oils in their diet. The authors add future researchers might assess the dose or amount of omega-3 that patients ingest, their prior omega-3 intake, and if trial participants are at risk for cardiovascular disease.

Let’s hope more clinical trials illuminate the issues surrounding the clinical efficacy of fish oils and address the current mystery why an anticipated dietary asset may not have a preventive impact for some diseases and conditions.

Meanwhile, provides a guide to fish oil consumption -- from either food or supplements -- within the ‘drugs and supplements’ section that is accessible on’s home page.’s fish oil page notes omega-3 supplements probably are safe for most persons as long as they are taken in low doses -- three grams or less per day.’s fish oil page adds the FDA approved a fish oil-based medication to reduce high triglycerides for persons with pancreatitis, a disease of the pancreas.’s fish oil page also reviews the evidence about fish oil’s clinical effectiveness within a comprehensive range of diseases and conditions, including depression, allergies, gum infection, and weight loss.’s fish oil page is located in` the ‘herbs and supplements’ section within the ‘drugs and supplements’ link on’s home page.

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