Researchers in China and US reported that fish oil supplementation was linked to 13% lower risk of all-cause mortality, 16% lower risk of CVD mortality, and 7% lower risk of CVD events in the general population.
In addition, they said that the association seemed stronger for CVD mortality than for the incidence of CVD, implying that fish oils could have a stronger effect in people with existing CVD conditions.
The findings were published in the medical journal, BMJ.
This study was funded by the Guangdong Province Universities and Colleges Pearl River Scholar Funded Scheme, Construction of High-level University of Guangdong, US National Institutes of Health/National Institute on Ageing, and National Natural Science Foundation of China.
Researchers used data from the UK Biobank study, which included participants from England, Scotland, and Wales.
A total of 427 678 men and women aged between 40 and 69 who had no CVD or cancer at baseline were enrolled between 2006 and 2010 and followed up until 2018.
Participants completed a questionnaire where they were asked about their intake of fish oil supplements, among others.
Fish oil supplement and outcomes
Findings showed 31.2% of the participants reported habitual fish oil supplementation at baseline.
Researchers said they found increasing intake of fish oil supplements was significantly associated with lower all-cause mortality as well as mortality from CVD events (p<0.05).
They reported that hazard ratios (HR) associated with fish oil supplements were 0.87 for all-cause mortality; 0.84 for CVD mortality; 0.80 for myocardial infarction mortality; 0.93 for CVD; 0.92 for myocardial infarction; and 0.90 for stroke.
This meant that a HR of 0.90 for stroke translated to a 10% lower risk of getting stroke.
In addition, for CVD events, the association seemed to be stronger among those with prevalent hypertension (p=0.005).
Researchers said their findings were similar in other RCTs as well as prospective cohort studies which found that omega 3 fatty acid, fish oil supplementation, and greater intake of fish were associated with lower risks of CVD outcomes.
According to them, fish oil supplements could be an inexpensive, quick, and safe way of increasing an individual’s omega 3 fatty acid intake, “Owing to its low cost, lack of fishy taste or smell, convenience of use, and mild side effects.”
Several mechanisms could explain the benefits for clinical outcome derived from fish oil supplementation.
“Firstly, the results of several studies have indicated that supplementation with omega 3 fatty acids has beneficial effects on blood pressure, plasma triglycerides, and heart rate, all of which would exert a protective effect against the development of CVD,
“Secondly, several trials have shown that omega 3 fatty acids can improve flow mediated arterial dilatation, which is a measure of endothelial function and health,
“Thirdly, omega 3 fatty acids have been shown to possess antiarrhythmic properties that could be clinically beneficial,
“Finally, studies have reported that fish oil can reduce thrombosis. Additionally, studies have reported that the anti-inflammatory properties of fish oil could have a preventive role in the pathophysiology of CVD outcomes,” researchers wrote.
However they note that there were still insufficient evidence to show which component of omega 3 fatty acids (docosahexaenoic acid or eicosapentaenoic acid) could be beneficial for CVD outcomes or all-cause mortality.
Strengths and limitations
Researchers described its huge population-based cohort was a strength of the study, although they acknowledged there were several limitations.
“The study did not record detailed information on the use of fish oil supplements, such as the dose, formulation, and duration of use. The lack of such information precluded us from evaluating dose-response associations between fish oil supplementation and outcomes, the independent effects and best ratio of the individual components of fish oil supplements, and the optimal duration of fish oil supplementation.”
They concluded that while their findings indicated habitual fish oil supplementation could have a marginal benefit for CVD outcomes, further studies are needed to examine how the dose of fish oil supplements affects its clinically meaningful effectiveness.
“Associations of habitual fish oil supplementation with cardiovascular outcomes and all cause mortality: evidence from a large population based cohort study”
Authors: Zhi-Hao Li, et al.
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