Fish Oil Supplements: Mixed Effects on Cardiovascular Health

Person taking a fish oil capsule
STUDY: Regular Fish Oil Use May Slow Existing Heart Disease But Increase Risk in Healthy People

The results of a large long-term study published in the open-access journal BMJ Medicine suggest that regular use of fish oil supplements may slow the progression of pre-existing poor cardiovascular health and lower the risk of death, but may increase rather than decrease the risk of first-time heart disease and stroke among those in good cardiovascular health.

Because it is an abundant source of omega-3 fatty acids, fish oil is advised as a dietary precaution to delay the onset of cardiovascular disease. However, the researchers note that there is conflicting information regarding the level of protection it provides.

They set out to evaluate the connections between fish oil supplements and new cases of atrial fibrillation, heart attacks, strokes, and heart failure, as well as mortality from any cause in individuals without a history of cardiovascular illness, to bolster the body of evidence.

Additionally, they evaluated the possible impact of these supplements on the likelihood of developing atrial fibrillation in the second stage, significant cardiovascular events such as a heart attack in the tertiary stage, and eventual death from heart disease (end-stage).

To obtain fundamental background information, they consulted 415,737 UK Biobank research participants (of whom 55% were women), who were polled between 2006 and 2010. This includes the fish oil supplements and oily and non-oily fish they typically eat.

Using information from medical records, the participants’ health was monitored until the end of March 2021 or until their death, whichever occurred first.

Thirty-one thousand six hundred people, or thirty-one percent, reported using fish oil supplements regularly. There were greater percentages of White, elderly, and female members of this group. The percentage of those who now smoke and those who reside in impoverished areas were lower, but alcohol consumption and the amount of oily to non-oily fish consumed were also higher.

Over an almost 12-year average follow-up period, 18,367 people experienced atrial fibrillation, 22,636 experienced a heart attack, stroke, or heart failure, and 22,140 passed away; 14,902 participants did not have atrial fibrillation or significant cardiovascular illness.

Of the individuals who went from having a healthy heart to having atrial fibrillation, 3085 experienced heart failure, 1180 a stroke, and 1415 a heart attack. Additionally, 2088 people who had suffered a stroke, 2098 people who had suffered a heart attack, and 2436 people who had heart failure passed away.

The results showed that regular usage of fish oil supplements had distinct effects on cardiovascular health, the course of disease, and death.

Regular use of fish oil supplements was linked to a 13% increased risk of developing atrial fibrillation and a 5% increased risk of having a stroke in individuals without a history of cardiovascular illness at the beginning of the monitoring period.

However, consistent use of fish oil supplements was linked to a 15% lower risk of progression from atrial fibrillation to a heart attack and a 9% lower risk of progression from heart failure to death among those who had a cardiovascular illness at the beginning of the monitoring period.

A more thorough investigation showed that the correlations found were altered by factors such as sex, age, smoking, eating non-oily fish, high blood pressure, and using blood pressure-lowering medications and statins. 

The risk of going from heart health to heart attack, stroke, or heart failure was 6% greater in women and 6% higher in non-smokers when regular use of fish oil supplements was involved. Furthermore, men (7% lower risk) and older participants (11% lower risk) benefited more from these supplements’ preventive effect on the transition from excellent health to mortality.

Recognize the researchers that because this is an observational study, no judgments about causal variables can be made. Furthermore, there was no information on the dosage or composition of the fish oil supplements that could have been of significance. Furthermore, they note that the results might not apply to individuals of other ethnic backgrounds because the majority of participants were White.

However, they come to this conclusion: “Regular use of fish oil supplements might have different roles in the progression of cardiovascular disease. Further studies are needed to determine the precise mechanisms for the development and prognosis of cardiovascular disease events with regular use of fish oil supplements.”

For more information: Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study, BMJ, 

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