A new study by Dutch scientists found that low doses of omega-3 fatty acids provided little to no help preventing future heart attacks in patients with a history of heart disease. As published in the New England Journal of Medicine, researchers followed 4837 patients for 40 months and gave each supplements containing docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), as found in fish oil, and/or alpha-linolenic acid (ALA), as found in certain nuts and vegetables. All patients had previously had a myocardial infarction (heart attack). By examining which patients had (another) MI during the 40 months of observation, the researchers determined that these fatty acids weren’t helping. Does this spell the end for fish oil supplements? Hardly. The Dutch work is important, but still leaves many questions unanswered.
This research comes in contrast with previous experiments which showed that fatty acids could significantly reduce the risks of heart attacks when taken regularly as a supplement. The nearly 5000 patients in the Dutch study received the Omega-3s in amounts comparable to previous tests (400mg for DHA/EHA or 2g for ALA per day – disguised in identical tasting sticks of margarine). But when comparing the recipients of supplements to those of placebo, the fatty acids didn’t seem to provide protection against MI. Of the 4800+ patients, 671 had a heart attack during the trial. The Dutch scientists, led by Daan Kromhout of Wageningen University, gave several reasons in their paper for why the discrepancy may have arisen.
The first idea is that the Dutch patients were mostly old men. Average age was 69 (range of 60 to 80) and 78% were male. Other tests for fatty acid supplements covered different ranges of age, and many focused on women. In fact, the Dutch researchers did find some indication that the women in the study benefited slightly from receiving ALA.
Another possible culprit (perhaps the most likely) is that all patients were receiving top of the line medical care. As all previously had experienced MI, they were being dosed with start of the art medications to prevent further heart attacks. 85% of the patients were taking statins. Kromhout and his colleagues suggest that this medical care may have had a profound enough life-saving effect that the bonuses from fatty acid supplements were negligible. If so, the experiment would not have been particularly insightful into the effects of omega-3s, but it would be a good sign that modern medicine really helps with MI.
The final major possibility is that the Dutch patients were outside the time in which fatty acids may have helped with heart disease. Patients had experienced their heart attacks an average of 4 years before the study began. Other trials for fatty acids had begun treating patients with supplements much closer to the original MI. There may be some optimal time after (or before) MI for taking fatty acids as a supplement.
I encourage you to read the NEJM article on this study – as far as medical publications go it’s pretty accessible. But I don’t think we can draw any definitive conclusions from this work. Yes, 4837 patients over 40 months is a good data set, but the study had its limitations as the authors discussed. As we mentioned earlier, a much larger study (20,000 patients) is forthcoming from the US National Institute of Health which should shed much needed light on the effects of fish oil and vitamin D. That study, however, will have its own limitations in terms of patient selection, just like the Dutch research. The truth is that while each study provides new data, we’re likely to need years of more trials before we can write the definitive word on fish oil. Hopefully, however, we’ll eventually collect enough information that we can reasonably understand if and when fatty acids will help protect your heart. When that happens we’ll have another tool in our kit for keeping us healthier and happier longer.
[image via thinkorthwim.com]
[source: Kromhout et al, NEJM 2010]
