Regular fish oil use may pose cardiovascular risk in those with no prior CVD

Key takeaways:

• Regular fish oil supplement use had different impacts on CVD progression depending on prior cardiovascular health.
• More studies are needed to further investigate the effects of regular fish oil supplementation.

Regular use of fish oil supplements was tied to an increased risk of stroke and atrial fibrillation in adults with no prior CVD, according to results of a large prospective cohort study published in BMJ Medicine.

In contrast, among adults with existing CVD, regular fish oil supplement use had beneficial effects on disease progression and risk for death.

According to Ge Chen, from Sun Yat-Sen University in China, and colleagues, findings from previous research on fish oil, cardiovascular health and related risk factors are controversial and have typically only focused on one health outcome.

“Whether fish oil could differentially affect the dynamic course of CVD is unclear,” they wrote.

The researchers assessed the effects of fish oil supplements on progression from good cardiovascular health, to atrial fibrillation, to major adverse cardiovascular events — such as heart failure, heart attack or stroke — to death.

The study included 415,737 participants aged 40 to 69 years (55% women) who were enrolled in the U.K. Biobank study.

Overall, 31.4% of participants reported regular fish oil supplement use at baseline, many of whom were older adults, white individuals and women.

During a median follow-up of 11.9 years, 18,367 participants had atrial fibrillation, 17,826 had major adverse cardiovascular events and 14,902 died without having atrial fibrillation or major adverse cardiovascular events.

Researchers found that regular fish oil supplement use was tied to an increased risk of developing atrial fibrillation (HR = 1.13; 95% CI, 1.1-1.17) and an increased risk of stroke (HR = 1.05; 95% CI, 1-1.11) in participants without CVD.

In comparison, among those with CVD, regular fish oil supplement use decreased the risk for:

• progression from atrial fibrillation to major adverse cardiovascular events (HR = 0.92; 0.87-0.98);
• progression from atrial fibrillation to myocardial infarction (HR = 0.85; 0.76-0.96); and
• progression from a heart attack to death (HR = 0.91; 95% CI, 0.84-0.99).

The association between regular fish oil supplement use and risk of major adverse cardiovascular events was greater in women (HR = 1.06; 95% CI, 1-1.11) and nonsmokers (HR = 1.06; 95% CI, 1.06-1.11).

The protective effects of supplement use on the progression from good cardiovascular health to death was greater in men (HR = 0.93; 95% CI, 0.89-0.98) and older participants (HR = 0.91; 95% CI, 0.86-0.96).

Additionally, smoking, age, consumption of non-oily fish, prevalent hypertension and the use of statins and antihypertensive drugs influenced the associations between regular fish oil supplement use and risk of atrial fibrillation.

Although the reason why fish oil supplements slowed CVD progression is unknown, the idea that omega-3 fatty acids protect the coronary artery “is biologically plausible,” Chen and colleagues wrote.

They also pointed out that the effects of omega-3 fatty acids could vary depending on an individual’s previous use of statins, “which might partly explain the different effects of fish oil supplements in people with and without CVD.”

Ultimately, Chen and colleagues urged caution when using fish oil or omega-3 fatty acid supplements for primary prevention due to potential adverse effects and uncertain cardiovascular benefits.

“Further studies are needed to determine whether potential confounders modify the effects of oil fish supplements and the precise mechanisms for the development and prognosis of cardiovascular disease events,” they concluded.

References:

• Chen G, et al. BMJ Med. 2024;doi:10.1136/bmjmed-2022-000451.
• Regular fish oil supplement use might boost first time heart disease and stroke risk. https://www.bmj.com/company/newsroom/regular-fish-oil-supplement-use-might-boost-first-time-heart-disease-and-stroke-risk/. Published May 21, 2024. Accessed May 21, 2024.