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Randomized trial · measured the question itself

Trial in 25,871 US adults: fish oil did not clearly change major heart events

Manson and colleagues · The New England journal of medicine · 2019

Original title: Marine n-3 Fatty Acids and Prevention of Cardiovascular Disease and Cancer.

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What the study found

No difference

Major heart events: 386 with omega-3 vs 419 with placebo (hazard ratio, 0.92; 95% CI, 0.80 to 1.06). Total heart attacks: 0.72 (95% CI, 0.59 to 0.90). Total stroke: 1.04. No extra bleeding was seen.

The study at a glance

Type of study
Randomized trial
Who or what was studied
25,871 people · men 50 and older and women 55 and older in the US, with no heart disease or cancer at the start
What was tested
1 g a day of fish-oil omega-3 versus placebo, median 5.3 years
What it measured
The question itself: heart attacks, strokes and heart deaths
Daily amount
1 g a day
How long
276 weeks
Trial registration
NCT01169259
Who has a stake
No disclosure in PubMed
Authors filed disclosure forms but no details in PubMed. Funded by the National Institutes of Health and others.
Journal
The New England journal of medicine, 2019
Source
PubMed record 30415637. This page is based on the abstract only.

How much this study counts

  • ✓Randomized: people were put into groups by chance, so the groups start out alike.
  • ✓Compared with a placebo, a dummy treatment.
  • ✓Large: 25,871 people.
  • ✓Long: about 5.3 years.
  • ✓Measured the question itself: heart attacks, strokes and heart deaths.
  • •The PubMed record has no conflict-of-interest statement.
  • •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

Each dot is one on-topic paper on this question. Steps near the top answer the question more directly.

↑ Stronger evidence

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

    11

    7 benefit, 4 no difference

    ↑ This study is the ringed dot

  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

Of the other 10 papers on the same step: 7 benefit, 3 no difference. This one found no difference. It differs from most of them.

Other papers on the same step

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 two reads differed. The reviewer checked the abstract and kept the first read. 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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