Prescription omega-3 fatty acid products containing highly purified eicosapentaenoic acid (EPA)

“Fish oil” is treated as one thing. This review insists it is not — and that the difference between its two main components has real consequences for the heart.

The distinction is between EPA and DHA, the two principal omega-3 fatty acids. Both lower triglycerides, but the authors marshal the pharmacology showing that DHA-containing formulations tend to raise LDL cholesterol in the process, while highly purified EPA lowers triglycerides without that penalty. For a patient being treated to reduce cardiovascular risk, nudging LDL upward to bring triglycerides down is a poor trade — which is the case for preferring an EPA-only prescription product.

The practical takeaway is targeted: in hypertriglyceridemic patients who also need to protect against cardiovascular events, the molecular details argue for purified EPA over mixed formulations or over-the-counter fish oil. The resistance is commercial — the makers of blended supplements and lightly regulated fish oils have little incentive to highlight the distinction.

We rate the evidence low. This is a well-referenced narrative review, but the authors carry commercial affiliations that favor EPA-only products, it offers no new data, and it predates the outcome trials that could confirm or refute its thesis. Its clinical significance is moderate and, in hindsight, looks better than it did at publication: the later REDUCE-IT trial lent weight to high-dose purified EPA, making this earlier mechanistic case for separating EPA from DHA more relevant than it first appeared. Read it as a hypothesis later partly vindicated — not as proof on its own.