Fish oil supplements and cardiovascular disease have had a long and controversial history. There was a lot of inconsistency in the research around supplementation and several organizations only added to this confusion. The incomplete reporting by media outlets have also confused the public.
Here, I’ll give a brief timeline of the evidence for fish oil and CVD outcomes.
- 1970s | A group of explorers noticed that people who consumed fish also had lower incidences of heart disease.
- 1980s-1990s | Early observational studies also saw a connection between fish consumption and heart disease risk
- 1990s | A few randomized trials were conducted to see the effects of fish oil supplementation and CVD outcomes
- 2002 |The American Heart Association put out a statement suggesting that fish oil supplementation was beneficial for fatal outcomes
- 2002 - 2016 | Several randomized trials and systematic reviews found inconsistent evidence for the effects of fish oil supplementation and CVD outcomes
- 2016 | The American Heart Association creates a scientific advisory group to look at all the evidence and concludes that despite the controversy, there was a small benefit from fish oil and it could be worth it for people who had a history of CVD events.
- 2018 | Large meta-analysis published in JAMA with 77,000 + participants found no benefit from fish oil supplementation on real clinical endpoints.
Let’s look at the evidence from the recent JAMA meta-analysis.
- fatal CHD
- nonfatal heart attacks
- major vascular events
- all-cause mortality
- Must be a randomized controlled trial
- Studies must have a minimum of 500 participants
- Studies must be at least one year long
- Studies must use fish oil supplements
Characteristics of Included Studies
- 10 randomized trials included
- 8 are double-blind, 2 are open label.
- Has a total of 77,000+ participants
- Average age: 64 years
- Average length of studies: 4.4 years
- Used mainly up to 1 g/d of fish oil (ranges: 226 to 1800 mg/day of EPA and 0 to 1700 mg/day of DHA)
- No statistically significant association between fish oil supplementation and any of the primary outcomes.
- However, the compatibility (confidence) intervals suggest very small effects.
- Up to a 7% decrease in the rate ratio is compatible with the test model.
- No significant differences amongst individual trials
- No associations found with subgroup analyses
- Strong statistical power/increased precision
- Only included studies of long duration
- Included studies were mostly at low risk of bias
- Used aggregated data instead of patient data
- Did not get a chance to add data from the REDUCE-IT trial or the STRENGTH trial which are using much higher dosages. (3-4 g/d of EPA)
Up to 1 g/d of fish oil may not have that much to offer when it comes to preventing CVD events in individuals who have a history of CVD. More research is currently underway on higher doses of fish oil supplementation, and there might be some promise there.