While fish oil supplements, rich in omega-3 fatty acids, are known to be good for heart health, a new study on May 22 showed that regular consumption may raise the risk of heart disease and stroke.

For the study, an international team of researchers from China, the UK, and the US analysed the health of 415,737 participants (55 per cent women), aged 40-69, who regularly consumed oily and non-oily fish and fish oil supplements.

The participants were surveyed between 2006 and 2010 and tracked until the end of March 2021 or death, whichever came first, based on medical records data.

Their results, published in the open-access journal BMJ Medicine, showed that regular use of fish oil supplements had different roles in cardiovascular health, disease progression, and death.

People with no known heart problems who regularly used fish oil supplements had a 13 per cent higher risk of developing atrial fibrillation, and a 5 per cent risk of a stroke.

The risk of transitioning from good health to heart attack, stroke, or heart failure was 6 per cent higher in women and 6 per cent higher in non-smokers.

In contrast, among those with known cardiovascular disease, regular fish oil supplements lowered the risk of progression from atrial fibrillation to a heart attack by 15 per cent, and from heart failure to death by 9 per cent.

Age, sex, smoking, consumption of non-oily fish, high blood pressure, and use of statins and blood pressure-lowering drugs were found to determine the associations observed.

Calling "this is an observational study, and no conclusions can be drawn about causal factors", the researchers stressed the need for further studies to determine the precise mechanisms.