Cod Liver Oil vs Omega-3 — What’s the Difference?

Last Updated May 2026 | Written by Chris Jones, Social Media Manager at Nutrivity with 7+ years in the supplement industry.

Cod Liver Oil vs Omega-3 — What’s the Difference?

This is one of the most common supplement questions in the UK, and the confusion is understandable — because cod liver oil is an omega-3 supplement. The two are not competing alternatives. Cod liver oil is a specific type of omega-3 source that also provides vitamins A and D. Standard “omega-3” or “fish oil” supplements provide EPA and DHA without those additional vitamins.

The real question is not “which is better” but “which is the right choice for your situation.” This guide explains exactly how they differ and helps you decide.

What Is Omega-3?

Omega-3 fatty acids are a family of polyunsaturated fats that the human body cannot produce — they must come from diet or supplements. The three main omega-3s are EPA (eicosapentaenoic acid), DHA (docosahexaenoic acid), and ALA (alpha-linolenic acid).

EPA and DHA are the forms with the strongest clinical evidence for health benefits. They are found primarily in oily fish (salmon, mackerel, sardines, anchovies) and marine sources. ALA is found in plant sources (flaxseed, chia seeds, walnuts) but the body converts very little ALA into EPA and DHA — typically less than 5%.

When you buy a “fish oil” or “omega-3” supplement, you are getting concentrated EPA and DHA extracted from the flesh of oily fish. The source fish varies by product — commonly anchovies, sardines, or mackerel.

What Is Cod Liver Oil?

Cod liver oil is extracted specifically from the liver of Atlantic cod. Because it comes from the liver rather than the flesh, it naturally contains fat-soluble vitamins that are stored in liver tissue — primarily vitamin A (retinol) and vitamin D3 (cholecalciferol) — alongside EPA and DHA.

This makes cod liver oil a fundamentally different nutritional proposition from standard fish oil. You are not just getting omega-3 — you are getting three beneficial nutrients in one supplement.

Nutritional Comparison

When Fish Oil Is the Better Choice

Standard fish oil is the better option if you specifically need a high dose of EPA and DHA — for example, if you are following a clinical protocol for triglyceride reduction (which typically requires 2–4g of EPA+DHA daily). Fish oil capsules generally deliver more omega-3 per capsule, making it easier to reach high therapeutic doses without consuming excess vitamin A.

Fish oil is also the better choice if you are already taking a separate vitamin D supplement and a separate vitamin A source, and simply want concentrated omega-3 without overlapping your other supplements.

When Cod Liver Oil Is the Better Choice

For most UK adults taking a general-purpose omega-3 supplement for cardiovascular health, joint support, and overall wellbeing, cod liver oil is the more efficient option because it provides three beneficial nutrients in one capsule.

This is particularly true in the UK context, where vitamin D deficiency affects approximately one in five adults and is even more prevalent during autumn and winter. Taking cod liver oil means you are addressing omega-3 intake and vitamin D status simultaneously — without needing a separate vitamin D supplement for the general maintenance dose.

Cod liver oil is also the better choice for joint health specifically. Omega-3 reduces inflammation while vitamin D contributes to normal muscle function and bone maintenance — both of which are directly relevant to joint conditions. When combined with glucosamine for cartilage support, cod liver oil addresses the inflammatory, structural, and nutritional components of joint health in a single strategy.

Nutrivity’s Cod Liver Oil & Glucosamine 1000mg combines cod liver oil with glucosamine in a single daily softgel at 17p per day. For more, see our best cod liver oil and glucosamine UK comparison and our guide to supplements to avoid with cod liver oil.

Vitamin A — The One Thing to Watch

Because cod liver oil contains vitamin A, there is a recommended upper limit to be aware of. Vitamin A is fat-soluble and accumulates in the body — excessive intake over time can cause toxicity. The UK tolerable upper intake level for vitamin A is 1500µg (5000 IU) per day for adults.

At standard supplemental doses (one to two capsules per day), cod liver oil is well within safe limits. The concern only arises if you are taking multiple supplements that all contain vitamin A, or if you eat liver (which is extremely rich in vitamin A) regularly. Pregnant women should be particularly careful with vitamin A intake and should consult their GP or midwife before taking cod liver oil.

What About Plant-Based Omega-3?

Vegan and vegetarian omega-3 supplements typically provide ALA from flaxseed or algal oil. Algal oil is the better plant-based option because it provides EPA and DHA directly (algae are the original source of omega-3 in the marine food chain — fish get their omega-3 from eating algae). Flaxseed oil provides ALA, which the body converts to EPA and DHA very inefficiently.

If you follow a plant-based diet and want omega-3, algal oil is the most effective option. For non-vegans, cod liver oil remains the most nutritionally comprehensive choice.

The Bottom Line

Cod liver oil and fish oil both provide EPA and DHA. The difference is that cod liver oil also delivers vitamins A and D naturally. Standard fish oil gives you more omega-3 per capsule. For most UK adults looking for general health, joint support, and cardiovascular benefit, cod liver oil is the more efficient choice because it covers omega-3 and vitamin D in one supplement — particularly important given the UK’s high rates of vitamin D deficiency.Key Takeaways

— Cod liver oil IS an omega-3 supplement — it provides EPA and DHA plus vitamins A and D

— Standard fish oil provides more concentrated omega-3 per capsule but no vitamins

— For high-dose omega-3 protocols (2–4g EPA+DHA), fish oil is more practical

— For general health and joint support, cod liver oil is more nutritionally complete

— Cod liver oil is particularly valuable in the UK where vitamin D deficiency is common

— Combining cod liver oil with glucosamine addresses inflammation, structure, and nutrition for joints

— Watch vitamin A intake if taking multiple supplements containing it

— Pregnant women should consult their GP before taking cod liver oil

Frequently Asked Questions