Something fishy about heart disease

Heart 1840
Human heart and lungs, drawn by W.Bagg, lithographed by William Fairfield and published by Jones Quain in 1840.
Credit: University of Liverpool

A meta-analysis of 15 major trials investigating the use of fish oil in people with heart disease has concluded that it can reduce the risk of death by around 10%.

However, the analysis, conducted by the American Heart Association (AHA), found no evidence for fish oil benefits in the general healthy population, and also declined to recommend its use for diabetics.

The AHA study, published in the journal Circulation, is the first update to clinical guidelines for fish oil since 2002. The oil, which contains omega-3 polyunsaturated fatty acid (known as PUFA), is one of the most popular dietary supplements in the world.

In investigating large randomly controlled trials conducted since the turn of the century the association found persuasive evidence for its role in reducing the risk of death in people with a history of heart attack or heart failure.

Curiously, the analysis also found that in general the protective effect of taking omega-3 supplements had declined since the 2002 clinical advice was issued. Earlier studies showed “large benefits” while later ones showed “no benefits”, the scientists report.

The AHA team, led by David Siscovick of the University of Maryland, suggests the finding is good news.

“With increasing public focus on omega-3 consumption, the background dietary consumption of fish in recent trials was generally higher than that observed in earlier studies,” the report states. This means that many people are already receiving the recommended dose of fatty acids, so taking additional in capsule form is having negligible effect.

And while this finding raises an obvious question about the continuing worth of fish oil as a clinically beneficial supplement, the AHA has decided that it is better to be safe than sorry for people with a history of heart problems.

“Treatment with omega-3 PUFA supplements is reasonable for these patients,” the report concludes. “Even a potential modest reduction in … mortality in this clinical population would justify treatment with a relatively safe therapy.”

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