Questions about omega-3 supplements come up in my practice almost every week. Patients want to know whether they should be taking fish oil, which brand is best, and whether krill oil is worth the extra cost. It is a topic surrounded by genuine interest — and genuine confusion.

The short answer is that for most people, getting omega-3 from food is better than getting it from a capsule. The longer answer involves understanding what the different supplement types actually are, what the evidence shows, and where the important caveats lie. This article works through each in plain terms.

If you have already read our article on the recent research linking high-dose fish oil to an increased risk of atrial fibrillation, this piece provides the broader context on omega-3 supplements and where they fit in a heart-healthy approach to nutrition. If you have not read it yet, it is worth doing so — the link is at the bottom of this page.

Why dietary sources come first

Before discussing supplements, it is worth being clear about why food sources of omega-3 are preferred. Fish — particularly oily fish like salmon, mackerel, sardines, and trout — provides omega-3 in a natural matrix alongside high-quality protein, vitamins, minerals, and other beneficial compounds that work together in ways a capsule simply cannot replicate.

Eating fish twice a week is one of the most consistently evidence-backed dietary recommendations in cardiovascular medicine. It is also, frankly, more enjoyable than swallowing a capsule — and considerably cheaper than many premium supplement brands.

My go-to quick lunch three to five times a week is a tin of tuna with some high-fibre crackers — a protein-packed meal for under 300 calories that takes about two minutes to prepare.

One thing I always tell patients about tinned tuna — check what it is packed in. Many flavoured varieties are in sunflower oil, sometimes with just a small percentage of olive oil listed on the label. I go for tuna in springwater and add my own drizzle of good extra virgin olive oil. With some steamed brown rice it is a genuinely excellent quick meal — balanced, filling, and heart-healthy.

Fish oil supplements

Fish oil is extracted from oily fish — typically anchovies, sardines, or mackerel — through a multi-step purification process that removes contaminants and concentrates the omega-3 content into a soft gel capsule. A reputable product will have been through molecular distillation to remove heavy metals and toxins, so quality matters when choosing a brand.

The omega-3 in fish oil is primarily in the form of triglycerides — the same basic fat structure found naturally in fish tissue. This is absorbed reasonably well, though some research suggests other formulations may be absorbed more efficiently.

Where does the evidence sit? Fish oil has the strongest data for reducing elevated triglyceride levels — the type of blood fat that rises with poor diet, excess alcohol, and metabolic conditions. For this specific use, the evidence is consistent and meaningful. The broader picture — whether fish oil supplements reduce the risk of heart attack and stroke in the general population — is less clear, and recent large studies have been mixed.

Importantly, recent research has also raised a dose-dependent concern about atrial fibrillation risk with higher-dose supplementation — particularly above one gram per day. This does not mean everyone taking fish oil needs to stop, but it is a conversation worth having with your doctor, particularly if you have any existing risk factors for AF.

Krill oil

Krill oil comes from tiny crustaceans — small shrimp-like creatures found in Antarctic waters. Like fish oil, it contains EPA and DHA, but in a different molecular form. In krill oil, the omega-3 fatty acids are bound to phospholipids rather than triglycerides, which some research suggests may allow them to be absorbed more efficiently by the body.

Krill oil also contains astaxanthin — a naturally occurring antioxidant that gives krill their distinctive pink colour — which may offer some additional anti-inflammatory benefit. The evidence for krill oil specifically is less extensive than for fish oil, so while it is a legitimate source of omega-3, it should not be assumed to be definitively superior. It also tends to be considerably more expensive.

One practical consideration — krill oil is derived from crustaceans, so anyone with a shellfish allergy should avoid it entirely.

Cod liver oil

Cod liver oil has the longest history of the three — generations of children were given a daily spoonful as a general health tonic. It is derived from the liver of cod rather than the flesh, which gives it a different nutritional profile. Alongside omega-3, it is a rich source of vitamins A and D, which makes it distinctive.

Vitamin D is genuinely valuable, particularly for people in lower-sunshine climates or those who spend most of their time indoors. Vitamin A is important for immune function and vision. However, vitamin A is also fat-soluble and accumulates in the body — meaning that excessive intake over time can become problematic. Cod liver oil should be taken in line with recommended doses and not combined with other high-dose vitamin A supplements without medical guidance.

For pure omega-3 benefit, cod liver oil is a reasonable option — but the vitamin A consideration makes it worth discussing with your doctor if you are taking it long-term.

Prescription omega-3 therapy

This is an entirely separate category that sometimes gets conflated with over-the-counter supplements — and they are not the same thing. Prescription-strength EPA preparations contain a highly purified, pharmaceutical-grade form of omega-3 and are used specifically for managing very high triglyceride levels, typically alongside statin therapy in people at elevated cardiovascular risk.

The evidence for certain prescription omega-3 preparations is meaningful in this specific setting. However, even at prescription doses, there is a documented association with an increased risk of atrial fibrillation — something that should be part of the shared decision-making conversation when this treatment is being considered.

If your doctor has prescribed an omega-3 medication, do not stop it without discussion. If you are taking over-the-counter supplements and wondering whether they offer the same benefit — they do not. The dose, formulation, and clinical context are entirely different.

Reading supplement labels — what to look for

If you do choose to take an omega-3 supplement, the label deserves careful attention. Several things are worth checking.

Questions to Ask Your Doctor

If you are considering starting or continuing an omega-3 supplement, these are worth raising at your next appointment:

Conclusion

For most people, the evidence points in the same direction — eat more oily fish, keep supplements as a secondary option if dietary sources are genuinely not achievable, and be thoughtful about dose if you do supplement. The difference between a can of good tuna in springwater with your own olive oil and a capsule of uncertain quality is more significant than most supplement marketing would have you believe.

If you do supplement, choose a reputable product, read the label carefully, keep the dose modest, and let your doctor know. And if your triglycerides are significantly elevated, that is a specific conversation to have about whether prescription therapy — not over-the-counter supplements — is appropriate for you.

The food-first message is not just a precaution — it is genuinely the best the evidence has to offer.

More from Heart Matters

• Is There Something Fishy About Fish Oil? — What the Latest Research Shows
• The Mediterranean Diet and Your Heart
• Atrial Fibrillation and Stroke Risk — What You Need to Know
• Understanding Cardiovascular Risk Factors