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AHA: Insufficient evidence for benefit of fish oil supplements in general population
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Eicosatetraenoic acid plus docosahexaenoic acid supplements may help prevent death in patients with recent MI or HF, but evidence is lacking to support use of the supplements for CVD prevention in the general population, according to an American Heart Association science advisory.
Approximately 18.8 million U.S. adults reported taking omega-3 fish oil supplements in 2012, according to David Siscovick, MD, MPH, senior vice president for research at the New York Academy of Medicine and chair of the advisory’s writing committee, and colleagues.
“People in the general population who are taking omega-3 fish oil supplements are taking them in the absence of scientific data that show any benefit of the supplements in preventing [MI], stroke, [HF] or death for people who do not have a diagnosis of [CVD],” Siscovick said in a press release.
In 2002, the AHA released a statement citing two trials suggesting the benefit of omega-3 fatty acid fish oil supplements on patients with prior clinical CHD. This update to the scientific statement focused on 13 additional trials that studied potential beneficial CV effects of fish oil supplements.
In addition to the two trials cited in 2002, three more trials examined the role of fish oil supplements in preventing CHD death, the panel wrote, noting that a meta-analysis of the studies shows reduction in CHD death and possibly a reduction in ischemia-induced sudden cardiac death in patients with prior CHD.
Little evidence
Several studies with MI as a secondary outcome have shown little evidence that fish oil supplements reduce the risk for stroke, and there are also no data that support supplements being used for prevention of secondary MI, according to the panel.
In a large randomized controlled trial in patients with HF with reduced ejection fraction, fish oil supplements were found to reduce mortality by 9% and CV-related hospitalization by 8%. No studies have been conducted on fish oil as a primary prevention for HF.
In one study, in the subgroup of participants with or at risk for diabetes, fish oil was not associated with a risk for death from CV causes. Other related studies had mixed findings.
In patients with high risk for CVD with and without clinical CHD, two of three studies found no benefit from fish oil supplements. In the third study, participants taking the supplement saw a RR reduction of 19% of a composite of major coronary events, including sudden cardiac death and MI, although 80% of participants had no prior clinical CVD, Siscovick and colleagues wrote.
Because of the conflicting evidence, there was a lack of consensus among the investigators on whether this treatment should be recommended for participants at high risk of CVD.
There have been no randomized controlled trials to date addressing fish oil supplements as a treatment to prevent incident CHD in populations without prior incidence; therefore, the authors made no recommendations pertaining to these populations.
Additionally, there was no evidence of fish oil having a beneficial effect on atrial fibrillation, either primary or secondary prevention or after cardiac surgery, according to the authors.
Reasonable for some
“Although recent [evidence from randomized controlled trials] has raised questions about the benefits of omega-3 supplementation to prevent clinical CVD events, the recommendation for patients with prevalent CHD such as a recent MI remains essentially unchanged: Treatment with omega-3 [fish oil] supplements is reasonable for these patients,” the researchers concluded. “Even a potential modest reduction in CHD mortality (10%) in this clinical population would justify treatment with a relatively safe therapy. We now recommend treatment for patients with prevalent [HF] without preserved left ventricular function to reduce mortality and hospitalizations (9%) on the basis of a single, large [randomized controlled trial].”
“Physicians should use this advisory as a guide to make decisions on whether omega-3 fish oil supplements might be appropriate for some patients,” Siscovick said in a press release. “The advisory concludes that supplementation with omega-3 fish oil may benefit patients with specific, clinical, [CVD] indications, including patients with a recent prior [MI and HF].” – by Cassie Homer
Disclosure: Siscovick reports no relevant financial disclosures. One researcher reports receiving research grants from Amarin, Amgen and Sanofi and serving on an advisory board for Amgen, AstraZeneca, Merck and Sanofi.
Perspective
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Kiyon Chung, MD
There is widespread use of fish oil supplementation in the general population, and it is a subject that comes up frequently in clinical practice. With these guidelines, practitioners will be much less likely to recommend fish oil supplementation unless the patient already has documented CAD or congestive HF with reduced ejection fraction. It is also important to note that the potential positive clinical effect even in these specific populations is rather small.
Research in this area has yielded mostly disappointing results in the past decade. The potential benefit of fish oil supplementation seems much weaker than one would have anticipated 2 decades ago. I agree with the authors that this is most likely to be explained by advances in treatment of CVD in general —especially the widespread use of statin medications, which could have weakened or negated the benefits of fish oil supplementation. It would be interesting to prospectively study whether fish oil supplementation could have a role in statin-intolerant patients with coronary disease.
The fish oil story raises the issue of whether clinical effects of older therapies may be negated by newer therapies that come along. Once a medication becomes part of accepted practice and guidelines, we seldom go back to retest its effects in the context of newer additive therapies. There is little incentive to study such questions, but it may be a question worth posing as we subject our aging patients to more polypharmacy.
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