Grand Rounds

Cochrane Review: Do Omega-3 Fatty Acids Reduce Cardiovascular Disease?

BACKGROUND AND PURPOSE:

There have been studies in the literature suggesting that omega-3 polyunsaturated fats may be protective against cardiovascular disease although literature is conflicting
- Omega-3 fats are ingested in the form of oily fish or fish oil (often fish liver) capsules and can also be plant based
  - Oily fish: long-chain omega-3 (LCn3), which includes eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA)
  - Plant based: Alpha-linolenic acid (ALA)
- There is professional guidance on this subject regarding the consumption of fish and some organizations also recommend supplementation for those with coronary artery disease (e.g., AHA)
There may be bias in previous studies, because fish consumption in some regions is associated with a more health-conscientious life style
Abdelhamid et al. (The Cochrane Library, 2018) sought to determine the impact of fish- and plant-based omega-3 on all-cause mortality, cardiovascular (CVD) events, adiposity and lipids
- Review commissioned by WHO to inform the next set of recommendations on polyunsaturated fatty acid intake in children and adults

Database search of RCTs and meta-analysis
- Studies lasting ≥12 months
- Intervention: Supplementation and/or advice to increase LCn3 or ALA (>10% of total fat) intake
- Control: Usual or lower intake
To avoid bias, two independent researchers assessed studies for inclusion, extracted data and assessed validity
Primary outcome: Long-chain omega-3 (LCn3, fish-based omega-3 fats) or ALA (plant-based omega-3 fats) fats and risk for
- All-cause mortality | Cardiovascular deaths | Cardiovascular events | Coronary heart disease deaths | Coronary heart disease events | Stroke | Arrhythmia | Adiposity and lipids
Secondary Outcomes: If omega-3 fatty acids are found to be effective, is protection
- Seen in both low and at high risk for cardiovascular disease
- Dependent on dose and duration
- Different depending if dietary or supplemental
GRADE methods used to assess result quality

79 RCTs were included
There was little or no effect of increasing LCn3 on
- All-cause mortality | Cardiovascular mortality | Cardiovascular events | CHD mortality | Stroke | Arrhythmia, CHD events
Increasing ALA intake made little to no difference for
- All-cause mortality | Cardiovascular mortality | CHD events
ALA enriched diet did reduce the risk of
- Cardiovascular events: Reduction from 4.8% to 4.7% – risk ratio (RR) 0.95; 95% CI, 0.83 to 1.07 (low-quality evidence)
- CHD mortality: Reduction from 1.1% to 1.0% – RR 0.95; 95% CI, 0.72 to 1.26 (moderate-quality evidence)
- Arrhythmia:Reduction from 3.3% to 2.6% – RR 0.79; 95% CI, 0.57 to 1.10 (moderate-quality evidence)
- Evidence for stroke unclear due to low-quality evidence

High-quality evidence demonstrated no benefit to EPA or DHA in the prevention of all-cause deaths and cardiovascular events
Moderate-quality evidence suggests that there is likely little or no difference for cardiovascular death, coronary deaths or events, stroke, or heart irregularities
Foods rich in omega-3 fats (such as walnuts, canola oil or enriched margarine)
- Likely makes little difference for all-cause or cardiovascular deaths or coronary events
- May protect against slightly reduce cardiovascular events, coronary mortality and heart irregularities

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