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Omega-3 fatty acids: no benefit on cardiovascular health?

Omega-3 fatty acids: no benefit on cardiovascular health?

Publication date: Wednesday, 10 October 2018

The most extensive systematic assessment of effects of omega‐3 fats on cardiovascular health to date suggests that increasing eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) has little or no effect on mortality or cardiovascular health. Previous suggestions of benefits from EPA and DHA supplements comes from trials with higher risk of bias whereas these studies (mainly supplement trials) provide moderate- and high-quality evidence. Low‐quality evidence suggests alpha-linolenic acid (ALA) from plants may slightly reduce CVD event risk, CHD mortality and arrhythmia.

This Cochrane review included 79 randomised controlled trials with over 112,000 participants. The trials all compared omega-3 supplementation with usual or lower intake and lasted at least 12 months.

Meta‐analysis and sensitivity analyses suggested little or no effect of increasing omega-3 on all‐cause mortality, cardiovascular mortality, cardiovascular events, coronary heart disease (CHD) mortality, stroke or arrhythmia. There was a suggestion that omega-3 reduced CHD events (RR 0.93, 95% CI 0.88 to 0.97, 84,301 participants; 5469 people experienced CHD events in 28 RCTs); however, this was not maintained in sensitivity analyses – and the authors said that omega-3 probably makes little or no difference to CHD event risk.

Increasing ALA intake probably makes little or no difference to all‐cause mortality (RR 1.01, 95% CI 0.84 to 1.20), cardiovascular mortality (RR 0.96, 95% CI 0.74 to 1.25), and it may make little or no difference to CHD events (RR 1.00, 95% CI 0.80 to 1.22). However, increased ALA may slightly reduce risk of cardiovascular events (from 4.8% to 4.7%, RR 0.95, 95% CI 0.83 to 1.07), and probably reduces risk of CHD mortality (1.1% to 1.0%, RR 0.95, 95% CI 0.72 to 1.26) and arrhythmia (3.3% to 2.6%, RR 0.79, 95% CI 0.57 to 1.10). Effects on stroke are unclear.

Key results from the omega-3 trial systematic review

No effects on:

  • Stroke (RR 1.06, 95% CI 0.96 to 1.16, 89,358 participants; 1822 strokes in 28 trials)
  • Cardiovascular events (RR 0.99, 95% CI 0.94 to 1.04, 90,378 participants; 14,737 people experienced events in 38 trials, high‐quality evidence)
  • All-cause mortality (RR 0.98, 95% CI 0.90 to 1.03, 92,653 participants; 8189 deaths in 39 trials, high‐quality evidence)
  • Cardiovascular mortality (RR 0.95, 95% CI 0.87 to 1.03, 67,772 participants; 4544 CVD deaths in 25 RCTs)
  • Coronary heart disease (CHD) mortality (RR 0.93, 95% CI 0.79 to 1.09, 73,491 participants; 1596 CHD deaths in 21 RCTs)
  • Arrhythmia (RR 0.97, 95% CI 0.90 to 1.05, 53,796 participants; 3788 people experienced arrhythmia in 28 RCTs).

 

ACTION

This systematic review provides little evidence to support the use of omega-3 supplements to improve cardiovascular health. A number of large trials are ongoing and their results will be valuable to compare with the findings of trials to date in this review. Any positive effects (risk reduction on CHD mortality, arrhythmia and CVD events) are likely to be small.  These findings suggest that official recommendations supporting omega-3 supplements should be reviewed.

Abdelhamid AS, et al. Omega‐3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database of Systematic Reviews 2018; Issue 7. Art. No.: CD003177. DOI: 10.1002/14651858.CD003177.pub3. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD003177.pub3/full

 

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Topics covered:
Category: Evidence in Practice
Edition: Volume 1 Number 1 PCCJ Online 2004

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