Fish oil is the second most popular supplement after multivitamins. Here is what controlled human research supports.

Established physiology

EPA and DHA contribute to normal heart function (EFSA-authorized, 250 mg/day threshold) and DHA contributes to maintenance of normal brain function and vision. These are nutrient-function claims, not treatment claims.

The trial record

Results differ by population and formulation. REDUCE-IT (2019) showed icosapent ethyl (a purified high-dose EPA drug) reduced cardiovascular events in high-risk patients on statins. In contrast, STRENGTH (2020) with a mixed EPA/DHA product was neutral. The lesson: formulation, dose, and baseline risk all matter.

Practical guidance

• Food first: 1–2 servings of oily fish per week aligns with most dietary guidelines.
• If supplementing, check the EPA+DHA content per serving (not “fish oil” grams) and choose products with third-party oxidation testing.
• People on anticoagulants should discuss fish oil with a physician — bleeding risk at high doses is debated but not zero.