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Pooled review (meta-analysis)

Pooled review of 86 trials found mixed results for fish oil and heart disease

Abdelhamid and colleagues · The Cochrane database of systematic reviews · 2020

Original title: Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease.

Under review. A person has not yet checked this summary against the paper. It is written from the PubMed abstract. Until a person checks it, search engines are asked not to list this page.

What the study found

Mixed

Little or no effect on all-cause death (RR 0.97, 95% CI 0.93 to 1.01), heart events (RR 0.96, 95% CI 0.92 to 1.01), stroke (RR 1.02) or arrhythmia (RR 0.99). Heart-disease events fell slightly (RR 0.91, 95% CI 0.85 to 0.97).

The study at a glance

Type of study
Pooled review (meta-analysis)
Who or what was studied
86 studies, 162,796 people · adults at varying heart risk, in 86 trials lasting 12 to 88 months
What was tested
Fish-oil omega-3 (EPA and DHA) from 0.5 g a day to over 5 g a day, versus placebo or usual intake
What it measured
The question itself: heart attacks, strokes and heart deaths
Who has a stake
No stake declared
All authors: none known. Funded by the UK Medical Research Council.
Journal
The Cochrane database of systematic reviews, 2020
Source
PubMed record 32114706. This page is based on the abstract only.

How much this study counts

  • ✓Pools the results of 86 studies with 162,796 people.
  • •A pooled review is only as strong as the studies it pools.
  • ✓Measured the question itself: heart attacks, strokes and heart deaths.
  • ✓No competing interests declared.
  • •Summarized from the PubMed abstract only. The full paper may hold details the abstract leaves out.

✓ Strength– Limit• Note

These points come from fixed rules about the type of study, its size and length, what it measured, and who has a stake. Every study on Digestery gets the same rules.

Where this study sits

This paper is not on the ladder. It is a pooled review (meta-analysis), and reviews and opinion pieces discuss studies that are already counted on the steps below.

↑ Stronger evidence

  1. Trials in people: heart attacks, strokes and heart deaths

    11

    7 benefit, 4 no difference

  2. Trials in people: other measures

    3

    1 benefit, 2 no difference

  3. Trials in people: lab tests or safety

    0

    None among the papers we read.

  4. Population studies

    0

    None among the papers we read.

  5. Blood levels and genes

    0

    None among the papers we read.

↓ Weaker evidence

  • Points to benefit
  • Mixed
  • No difference
  • No direction
  • Points to harm

How it fits with the other research

The short answer to “Does fish oil prevent heart disease?”

Little or no effect in most trials.

Confidence: moderate. Based on 21 on-topic papers.

Read the full answer
  • Quoted in “What we found”: A 2020 review of 86 trials (162,796 people) found little or no effect on death from any cause (RR 0.97) or on heart and stroke events (RR 0.96).
  • Part of the finding “Big reviews find little or no overall effect”.
  • Part of the finding “Irregular heartbeat and bleeding showed up as harms”.
  • Summed up in “What reviews found”: Pooled 86 trials with 162,796 people. Found little or no effect of fish omega-3 on deaths, strokes or overall heart events, and a slight drop in coronary heart disease events and deaths, on low-certainty evidence.
  • Marked as a key paper in the research timeline: Biggest review: 86 trials, small coronary drop.

Other reviews on this question

See all 21 studies on this question

How this page was made

Label

First read of the abstract
Claude Sonnet
Independent second read
Claude Haiku
Differences settled
The reviewer corrected 1 field after reading the abstract. Claude Opus 5.5.
Headline
Claude Sonnet, from the checked study record. A script checked its numbers and wording.
Numbers
Checked against the abstract by a script
“How much this study counts”
Fixed rules, the same for every study
Source check by a person
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