Study: Fish oil supplements increase the risk of heart disease in healthy people

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Fish oil is a rich source of omega-3 fatty acids and is often recommended as a preventive diet to stave off the development of cardiovascular disease.

But a new study, which included more than 415,000 Britons, found that taking common fish oil supplements can increase the risk of heart disease and stroke in healthy adults, while reducing the risk in those with a history of the disease.

The research team, led by Sun Yat-Sen University in China, studied the association between fish oil supplements and cases of atrial fibrillation, heart attacks, strokes and heart failure, which causes death.

About a third of participants (130,365), aged 40 to 69, said they regularly use fish oil supplements, including a large number of older people, people of color and women.

The team evaluated the effect of these nutritional supplements in relation to the risk of going from good heart health to secondary stage atrial fibrillation and third stage major cardiac events, such as heart attack and death.

After 12 years of follow-up, 18,367 people developed atrial fibrillation and irregular heartbeat, 22,636 had a heart attack, stroke, or heart failure, and 22,140 people died.

Of those who had heart failure, 2,436 people died, 2,088 people died of a stroke, and 2,098 people died after a heart attack.

The results showed that the use of fish oil supplements played different roles in cardiovascular health, disease development, and death.

It turned out that those who used it regularly (without any signs of illness) experienced a 13% higher risk of developing atrial fibrillation, and a 5% increased risk of stroke.

Regular use of fish oil supplements among those who already had cardiovascular disease reduced the risk of the disease progressing from atrial fibrillation to a heart attack by 15%, and from heart failure to death by 9%.

The risk of going from good health to having a heart attack, stroke or heart failure was 6% higher for women. The percentage was also 6% higher among non-smokers among fish oil users.

Meanwhile, the protective effect of these supplements on the transition from good health to death was greater in men (7% risk reduction) and older participants (11% risk reduction).

The researchers acknowledged that there were limitations to the study, including not recording the dose and composition of fish oil, which may be key to the results.

The results were published in the journal BMJ Medicine.