Regular use of fish oil supplements may be linked to a lower risk of death and cardiovascular disease (CVD) events, such as heart attack and stroke, suggests an analysis* of data from the UK Biobank study, published in The BMJ.
However, further studies are needed to explore what dose is needed to achieve a clinically meaningful effect, the researchers said.
Although some previous studies suggested that omega-3 fatty acids in fish oil may help prevent CVD and reduce mortality, conclusive evidence is still lacking.
A team of researchers based in China and the US analysed data on 427,678 men and women aged between 40 and 69 -years-old, without CVD or cancer, who were enrolled in the UK Biobank study - a large population based study of more than half a million British men and women – from 2006 to 2010, and who had completed a questionnaire on supplement use, including fish oil.
Death certificates and hospital records were used to monitor deaths from any cause, CVD deaths, and CVD events, such as heart attack and stroke, through to 2018.
Almost a third (31%) of participants reported taking regular fish oil supplements at the start of the study and the researchers found that fish oil supplements were associated with a 13% lower risk of all-cause mortality, a 16% lower risk of CVD mortality, and a 7% lower risk of CVD events (388 fewer all-cause deaths, 124 fewer CVD deaths, and 295 fewer CVD events per 100,000 people in a median follow-up of nine years).
The association between fish oil use and CVD events appeared to be stronger among those with high blood pressure.
These favourable associations remained after taking account of traditional risk factors, such as age, sex, lifestyle habits, diet, medication and other supplement use.
The researchers said several mechanisms could explain the research. For example, omega-3 fatty acid supplements have shown beneficial effects on blood pressure, cholesterol levels, and heart rate, all of which would exert a protective effect against the development of CVD events.
This is an observational study, so can't establish cause, and the researchers said there was also a lack of information on dose, duration, and side effects of fish oil use.
They concluded that habitual fish oil use "is associated with a lower risk of all-cause and CVD mortality and a marginal benefit against CVD events among the general population and that future studies are needed to address the extent to which the dose of fish oil supplements influences the ability to achieve a clinically meaningful effect."
*Zhi-Hao L, Wen-Fang Z, Simin L, et al. Associations of habitual fish oil supplementation with cardiovascular outcomes and all cause mortality: evidence from a large population based cohort study. BMJ 2020; 368 :m456