Too much of a good thing? The latest on omega 3 for heart health
You may have seen a recent release published by the Medicines and Healthcare products Regulatory Agency (MHRA) advising vigilance over a link between omega-3 intake and a condition called atrial fibrillation. You may also have seen reports over recent years about this in the media so this is not a new finding.
We advise many of our community on the use and benefits of omega-3. The effects of omega-3s, such as eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids, on cardiovascular risk prevention have been debated. However, the evidence is mounting for their benefits, as well as elaborating on the potential previous confounding issues that may have led to the questions over their benefits. Aside from their more commonly discussed cardiovascular effects, they are also linked with cognitive function and all-cause mortality benefits.
The main paper leading to this review published by the MHRA was in patients with established or elevated cardiovascular risks. As such, this cannot be generalised to a healthy population where no increased risk of atrial fibrillation was found in a recent randomised controlled trial.
Overall benefits of having a sufficient intake of omega-3 is likely to be positive; a 2021 analysis of 38 studies published in a Lancet journal covering 150,000 participants, found omega-3 medication intake, and particularly EPA, was associated with reduced cardiovascular mortality, non-fatal heart attacks and other major adverse cardiovascular events (MACE).
However, the authors of this paper accepted that there appears to be a consistent association of omega-3 medication intake with the risk of a condition called atrial fibrillation (5.4 cases per 1000 person-years; or a relative risk of 1.26). The risk appears to be dose-related and only above an intake of 1g per day, with the highest risk at 4g per day, and in a high risk population.
One of the most clinically relevant implications of having atrial fibrillation is the risk of stroke. However, a review of studies in 2022 found that despite the increased atrial fibrillation associated with omega-3 trials, there was no increased risk of stroke.
Interestingly, it seems that EPA could not only account for some of the benefits of omega-3 on the cardiovascular effects as discussed above but may explain the majority of the atrial fibrillation risk too.
An objective way to measure the effects of omega-3 intake is the level of EPA+DHA in blood or tissues, which is largely determined by habitual dietary intake of omega-3. A research article published this month, which pooled the findings of 29 previous prospective studies found that the highest quintile of blood levels of EPA & DHA were, in fact, associated with a relative reduction in stroke risk of 12-17% compared to the lowest quintile and that blood levels of EPA were not associated with incident atrial fibrillation.
Of note, the MHRA advised that “neither the randomised controlled trials or the review evaluated dietary consumption of fish and other foods rich in omega-3 nor supplements”.
So what can we concluded from this recent MHRA publications? Whilst all recommendations should be weighed up individually and be made aware of the risks, such as atrial fibrillation, for those not at high risk of atrial fibrillation or cardiovascular disease, the overall adverse effects of omega-3s are likely to be very small. Sufficient dietary intake is a good place to start before considering objectively checking blood levels to guide any supplemental intake.
