Heart disease remains the leading cause of death in the UK. Yet one of the most studied, most accessible nutritional tools for protecting your heart sits on the shelf in most health food shops.
Omega 3 fatty acids have decades of clinical research behind them. The evidence is not perfect — no nutritional science is. But the overall picture is compelling. If you care about your cardiovascular health, omega 3 deserves serious attention.
What Omega 3 Does in the Cardiovascular System
Omega 3 fatty acids — particularly EPA (eicosapentaenoic acid) and DHA (docosahexaenoic acid) — work across several interconnected pathways in the cardiovascular system.
They reduce triglycerides, lower blood pressure and reduce arterial inflammation.
Improve the flexibility of red blood cells, helping them move through small capillaries more efficiently.
They also reduce platelet aggregation — the tendency of blood cells to clump together — which lowers the risk of dangerous clot formation.
None of these effects work in isolation. Together, they create a cardiovascular environment that functions more safely and more efficiently.
The Triglyceride Evidence
The most consistent finding across omega 3 research is its effect on triglycerides — the fats that circulate in your bloodstream. High triglyceride levels increase the risk of coronary artery disease, stroke, and metabolic syndrome.
Omega 3 supplementation reliably and significantly reduces triglyceride levels. The American Heart Association reviewed the evidence and concluded that doses of 2–4 grams of EPA and DHA per day can reduce triglycerides by 20–30%. This effect is dose-dependent and well-replicated across populations.
The FDA has approved a prescription-strength omega 3 drug — Vascepa — specifically for reducing triglycerides in high-risk patients. The active ingredient is purified EPA. This is not fringe science. The triglyceride-lowering effect of omega 3 is established medicine.
Blood Pressure and Arterial Health
High blood pressure is one of the most significant modifiable risk factors for heart attack and stroke. Omega 3 helps here too.
A meta-analysis published in the American Journal of Hypertension analysed data from 70 randomised controlled trials. Higher doses of omega 3 — particularly above 2 grams per day — produced meaningful reductions in both systolic and diastolic blood pressure. The effect was strongest in people with existing hypertension and in older adults.
Omega 3 also supports endothelial function — the health of the inner lining of your blood vessels. A healthy endothelium keeps vessels flexible, regulates blood flow, and resists the build-up of arterial plaque. Chronic inflammation damages the endothelium. Omega 3 combats that inflammation directly.
The REDUCE-IT Trial: A Landmark Moment
For years, critics argued that while omega 3 improved biomarkers, the evidence for actual cardiovascular outcomes — heart attacks, strokes, deaths — was mixed. Then came the REDUCE-IT trial.
Published in the New England Journal of Medicine in 2018, REDUCE-IT followed over 8,000 high-risk patients for nearly five years. Participants taking 4 grams of purified EPA daily reduced their risk of major cardiovascular events — including heart attack and stroke — by 25% compared to the placebo group.
What About Regular Supplementation for Healthy Adults?
REDUCE-IT used high therapeutic doses in high-risk patients. Does everyday supplementation at lower doses still deliver cardiovascular benefit for generally healthy people?
The evidence here is more nuanced. A 2018 Cochrane review found that moderate omega 3 supplementation in the general population produced inconsistent effects on cardiovascular events. This prompted some headlines claiming omega 3 “doesn’t work.”
But a closer look tells a different story. Most standard fish oil supplements deliver only 300–500mg of combined EPA and DHA per capsule. The doses used in effective clinical trials typically range from 1,000mg to 4,000mg. Many studies showing weak effects used low-dose supplements in populations with already-adequate intake.
Dose matters. Source quality matters. And consistent, long-term supplementation matters far more than occasional use.
Getting the Dose Right
For general cardiovascular support, aim for at least 1,000mg of combined EPA and DHA per day from a high-quality supplement. For people with elevated triglycerides or existing heart disease risk, 2,000–4,000mg delivers greater benefit — ideally under medical guidance.
Check the label carefully. A 1,000mg fish oil capsule often contains only 300mg of actual EPA and DHA. The rest is other fats. Always look for the EPA and DHA content specifically, not just the total fish oil dose.
The Bottom Line
Omega 3 protects the heart through multiple, well-evidenced mechanisms. It reduces triglycerides, lowers blood pressure and fights arterial inflammation. At higher therapeutic doses, it demonstrably reduces the risk of major cardiovascular events.
The key is getting enough of it, consistently, from a supplement you can trust.