Recent research findings suggest that fish oil supplements might increase the risk of someone developing a heart condition or stroke, but could reduce the risk for those who already have cardiovascular disease.
Fish oil is a rich source of omega-3 fatty acids and the NHS recommends at least one portion of oily fish a week to help prevent the development of cardiovascular disease, reports The Guardian.
To find out how much protection it affords, a team of researchers in China, the US, the UK and Denmark monitored the health of more than 400 000 participants in the UK Biobank for an average of 12 years to estimate the associations between fish oil supplements and new cases of atrial fibrillation (irregular heartbeat); heart attack, stroke and heart failure; and death in people with no known cardiovascular disease.
They also assessed whether these supplements affected the progression of heart conditions.
Published in the journal BMJ Medicine, the study found that for those with no known cardiovascular disease at the start of the monitoring period, regular use of fish oil supplements was associated with a 13% heightened risk of developing atrial fibrillation and a 5% heightened risk of having a stroke.
But for patients with heart disease at the beginning of the study period, fish oil supplements were associated with a 15% lower risk of progressing from atrial fibrillation to a heart attack, and a 9% lower risk of progressing from heart failure to death.
The benefits and risk of omega-3 supplementation were not uniformly observed, the study noted. The risk of healthy patients going on to have a heart attack, stroke or heart failure was 6% higher in women and 6% higher in non-smokers.
There was also a greater beneficial effect for older people and men with existing heart conditions, where the risk of transition from good health to death was 11% and 7% lower respectively.
This was an observational study, so no conclusions can be drawn about causal factors, the authors caution. And no information was available on either dose or formulation of the fish oil supplements.
Given that most of the participants were white, the findings might not be applicable to people of other ethnicities, they add.
Tracy Parker, a senior dietician at the British Heart Foundation, said: “This research shouldn’t be concerning to people who regularly take fish oil supplements, but it’s also not a green light to start taking them to prevent heart and circulatory diseases.
“In the UK, NICE guidelines don’t recommend taking fish oil supplements to either prevent heart and circulatory diseases or stop another heart attack. Supplements like omega-3 fatty acids are no substitute for a healthy diet and, instead of focusing on individual nutrients, it’s important for people to look at diet as a whole to help lower any risk.”
She said the the traditional Mediterranean diet has repeatedly been shown to reduce the risk of heart attack or stroke.
Study details
Regular use of fish oil supplements and course of cardiovascular diseases: prospective cohort study
Ge Chen, Junguo Zhang, Hualiang Lin et al.
Published in The BMJ on 21 May 2024
Abstract
Objective
To examine the effects of fish oil supplements on the clinical course of cardiovascular disease, from a healthy state to atrial fibrillation, major adverse cardiovascular events, and subsequently death.
Design
Prospective cohort study.
Setting
UK Biobank study, 1 January 2006 to 31 December 2010, with follow-up to 31 March 2021 (median follow-up 11.9 years).
Participants
A total of 415 737 participants, aged 40-69, enrolled in the UK Biobank study.
Main outcome measures
Incident cases of atrial fibrillation, major adverse cardiovascular events, and death, identified by linkage to hospital inpatient records and death registries. Role of fish oil supplements in different progressive stages of cardiovascular diseases, from healthy status (primary stage), to atrial fibrillation (secondary stage), major adverse cardiovascular events (tertiary stage), and death (end stage).
Results
Among 415 737 participants free of cardiovascular diseases, 18 367 patients with incident atrial fibrillation, 22 636 with major adverse cardiovascular events, and 22 140 deaths during follow-up were identified. Regular use of fish oil supplements had different roles in the transitions from healthy status to atrial fibrillation, to major adverse cardiovascular events, and then to death. For people without cardiovascular disease, hazard ratios were 1.13 (95% confidence interval 1.10 to 1.17) for the transition from healthy status to atrial fibrillation and 1.05 (1.00 to 1.11) from healthy status to stroke. For participants with a diagnosis of a known cardiovascular disease, regular use of fish oil supplements was beneficial for transitions from atrial fibrillation to major adverse cardiovascular events (hazard ratio 0.92, 0.87 to 0.98), atrial fibrillation to myocardial infarction (0.85, 0.76 to 0.96), and heart failure to death (0.91, 0.84 to 0.99).
Conclusions
Regular use of fish oil supplements might be a risk factor for atrial fibrillation and stroke among the general population but could be beneficial for progression of cardiovascular disease from atrial fibrillation to major adverse cardiovascular events, and from atrial fibrillation to death. 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.
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