Posted: Wednesday, August 19, 2009
A new review concludes that there is extensive evidence from three decades of research that fish oils, or more specifically the omega-3 polyunsaturated fatty acids (PUFAs) contained in them, are beneficial for everyone and that it can reduce the risk for total mortality, sudden death, CHD mortality, and cardiovascular mortality by as much as 30%.
This includes healthy people as well as those with heart disease — including postmyocardial infarction (MI) patients and those with heart failure, atherosclerosis, or atrial fibrillation — say Dr. Carl J. Lavie, Ochsner Medical Center, New Orleans, Louisiana, and colleagues.
Lavie stated that, “We reviewed everything that was published on omega-3 that was clinically important, and the major finding is that there are a tremendous amount of data to support the benefits of omega-3, not just as a nutritional supplement — people have known that for years — but evidence that it prevents and treats many aspects of cardiovascular disease.”
Lavie said he believes physicians are not as familiar with the omega-3 studies as they should be, “Clinicians know the findings of many statin trials even if they do not know all the details — they know that there are a ton of statin data. The omega-3 data may not be as impressive or as plentiful as this, but it should be ‘promoted’ to clinicians.”
Omega-3 PUFA, says Lavie, “is a therapy that clinicians should be considering prescribing to their patients. Not just as something healthy but as something that may actually prevent the next event. In HF [heart failure], it may prevent death or hospitalization and the same thing post-MI.” He and his colleagues reiterate the advice of the American Heart Association (AHA): that those with known coronary heart disease (CHD) or HF eat four or five oily-fish meals per week or take the equivalent in omega-3 supplements; healthy people should consume around two fatty-fish meals per week or the same in supplements.
In their review, Lavie and colleagues explain that most of the data on omega-3 have been obtained in trials using docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), the long-chain fatty acids in this family. The most compelling evidence for cardiovascular benefits comes from four controlled trials of almost 40,000 participants randomized to receive EPA with or without DHA in studies of primary prevention, after MI, and most recently with HF, they note.
They discuss the results for each specific cardiovascular condition in turn. For CHF, three large randomized trials — the Diet and Reinfarction Trial (DART), the Gruppo Italiano per lo Studio della Sopravvivenza nell’ Infarto Miocardico (GISSI) -Prevenzione, and the Japan EPA Lipid Intervention Study (JELIS) — have indicated that omega-3 PUFAs lower CV risk in both the primary- and secondary-prevention settings, they note.
Lavie elaborated that,”The benefit is different in different studies but can be as much as 30%.” The effects are seen on total mortality, sudden death, CHD mortality, and cardiovascular mortality.
There is also evidence of benefit in atherosclerosis and in a wide range of arrhythmias, with the most significant effect and potential benefit seen in “the current epidemic” of atrial fibrillation (AF), note the researchers. But more studies are needed to explore the effects of various doses of omega-3 PUFAs on the primary and secondary reduction of AF and to determine whether the benefits are caused by antiarrhythmic effects, benefits on autonomic tone, or even anti-inflammatory effects, they observe.
Recently, the potential benefits of omega-3 PUFAs “have been extended to the prevention and treatment of HF,” say Lavie et al. Although the reduction in events was “only 8% to 9% in the recent GISSI-HF trial, which is not huge,” Lavie admits, “when you think of HF, it’s a very serious disorder, and in GISSI-HF, those patients were treated vigorously for their HF, so they were on good therapy, and adding just one [omega-3 PUFA] pill a day reduced deaths by between 8% and 9%, which is a pretty nice additional benefit.”
But he and his colleagues say further studies are needed to determine the optimal dosing of omega-3 PUFA for different stages of HF and to investigate the underlying mechanisms for the benefits. However, in the meantime, omega-3 PUFA supplements “should join the short list of evidence-based life-prolonging therapies for HF.”
They also discuss the data on omega-3 PUFAs in hyperlipidemia, noting that the FDA has approved one such supplement for the treatment of very high triglyceride levels.
And they note that more studies are needed to determine the optimal mix of DHA relative to EPA in various populations.
Finally, they state that this review does not focus on the plant-based precursor of EPA, alpha-linolenic acid (ALA), which is found in abundance in flaxseed and to a lesser extent in other plants. But they observe, “The overall evidence is much weaker for ALA than for EPA and DHA.”
Mirroring recommendations from the AHA, European Society of Cardiology, and the World Health Organization (WHO), Lavie and colleagues recommend that healthy people consume at least 500 mg per day of EPA/DHA — equal to around two fatty-fish meals per week — and that those with known CHD or HF get 800 to 1000 mg per day EPA/DHA.
When asked whether people should try to consume more fish or alternatively take supplements, Lavie says, “If somebody really were eating salmon and tuna and mackerel and sardines, and they were doing that several times a week, then they wouldn’t need to be taking a supplement. But in the US, at least, very few people are going to eat the therapeutic doses of fatty fish.”
Other good reasons to take supplements include the fact that they have usually had impurities, such as mercury, removed, he notes.
If people are trying to improve their consumption of oily fish, they could take supplements only on the days they were not eating such fish or every other day to try to get up to the recommended amount of omega-3 PUFAs, Lavie says.
But he warns that regimens that are too complex might result in underconsumption. “I would tend to think that most people are getting very little omega-3 PUFAs in the diet. There’s no harm in taking extra — the only negative of extra is the calories. I don’t think anyone thinks now that fish oil is doing any harm.”