Fish oil

The largest review, 86 trials and 162,796 people, found little or no effect on death, cardiovascular events, stroke or arrhythmia. A 4 g/day prescription EPA drug did lower events in people already treated for heart disease or diabetes, but it increased hospitalization for atrial fibrillation. Higher doses carry more of that rhythm risk.

The research points to food, not the clock. In a small 1988 trial, taking fish oil with a high-fat meal raised EPA absorption from the natural triglyceride form from 69% to 90%, and roughly tripled absorption from the ethyl ester form. Nothing shows morning beats evening; pick a meal you eat reliably.

The most common are mild: a fishy aftertaste, burping and nausea. A pooled analysis of 21 trials of prescription-strength omega-3 (24,460 people) also found more skin reactions than placebo, with no clear evidence of serious adverse events. Those doses were well above a typical softgel, so effects at lower doses may be milder.

Fish oil has a weak antiplatelet effect on its own. A literature review found it becomes more noticeable alongside antiplatelet drugs and, to a lesser extent, warfarin or factor Xa inhibitors. Alone, it was not linked to a meaningful rise in surgical bleeding. Tell your doctor or surgeon before combining or before a procedure.

Evidence is weak. A 2021 Cochrane review found a small effect on depressive symptoms, rated very low certainty and unlikely to matter clinically. A 2024 dose-response analysis found anxiety benefit only at 2 g/day or more, also with very low certainty. EPA-dominant products looked better than DHA-dominant ones for depression.