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Docosahexaenoic Acid (DHA) Responsible for Heart Rate Lowering Effect of Omega-3s

6/5/2018 4:28:01 PM
Long-chain polyunsaturated fatty acids (n-3 LCPUFAs) have been extensively studied for their cardioprotective effects. Several studies suggest that n-3 LCPUFAs reduce the risk of sudden cardiac death, and it has been suggested that they do so by reducing resting heart rate. A meta-analysis to evaluate the effect of n-3 LCPUFAs on HR was published in 2005 and included 30 randomized controlled trials (RCTs) with 1678 participants. Since that time, many more RCTs have been conducted on this topic. A meta-analysis, published in 2018, updated the evidence on the effect of n-3 LCPUFAs on HR reduction and further explored the differential effects of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA).
The analysis included 51 RCTs with 3000 participants. The intervention variable in all included studies was n-3 LCPUFA supplementation or fatty fish consumption, and the outcome variable was heart rate. Healthy participants represented 24 intervention groups, and participants with at least one chronic condition represented 32 intervention groups. The duration of the trials ranged from 2 weeks to 1 year. The mean heart rate of the participants was within the normal range in almost all of the trials. The dosage of EPA plus DHA ranged from 0.5 to 15 g/day. Ten studies separately evaluated the effects of EPA and DHA. Most trials reported no significant side effects.
The change in heart rate between the intervention and control groups ranged from 0 to 10 bpm. Compared with placebo, n-3 LCPUFA supplementation mildly but significantly reduced heart rate by 2.23 bpm (95% CI, -3.07 to -1.40 bpm). There was moderate heterogeneity among trials but low risk of bias. When comparing the individual effects of EPA and DHA, only DHA supplementation significantly reduced heart rate (-2.47 bpm; 95% CI, -3.47 to -1.46 bpm).
This meta-analysis updates and strengthens the evidence that n-3 LCPUFAs reduce heart rate. A unique finding of this study is that DHA, rather than EPA, is responsible for this effect. The authors conclude that consumption of fatty fish and supplementation with n-2 LCPUFAs should be considered in patients at risk of sudden cardiac death and other cardiovascular conditions.  
Hidayat K, Yang J, Zhang Z et al. Effect of omega-3 long-chain polyunsaturated fatty acid supplementation on heart rate: a meta-analysis of randomized controlled trials. Eur J Clin Nutr. 2017.