Researchers have been evaluating earlier studies suggesting that omega-3 fatty acids (EPA and DHA) improve cardiovascular health by lowering the risk of heart attack and related conditions. Some recent findings, however, have raised questions about whether certain fish oil formulations may worsen certain outcomes.
The STRENGTH trial, completed in 2020, evaluated whether a high dose (4 g/day) of a prescription EPA/DHA omega-3 formulation improved cardiovascular outcomes in an at-risk population compared with corn oil.
Following the success of the REDUCE-IT trial, which studied a purified EPA formulation, many experts expected similar benefits from the EPA/DHA combination. However, the STRENGTH trial was stopped early because it showed no cardiovascular benefit compared with placebo.
Additionally, the trial observed a 67% increase in atrial fibrillation, a potentially serious arrhythmia associated with increased stroke risk.
One important detail may help explain the difference between these trials: blood EPA levels in STRENGTH participants were less than half of those achieved in the REDUCE-IT trial. This finding suggests that achieving a sufficiently high EPA level may be necessary to obtain cardiovascular benefit.