Fish Oil vs Cod Liver Oil: Omega-3, Vitamins A and D, and Which Question Each Answers
Fish oil and cod liver oil both contain EPA and DHA, but cod liver oil also carries vitamins A and D. See the documented differences, official limits and safety points.
Content last updated . This page has not been medically reviewed.
The question each oil answers
People often ask whether cod liver oil is "just" fish oil. It is not quite. NCCIH describes fish oil supplements as containing EPA and DHA. It describes fish liver oil supplements, such as cod liver oil, as containing EPA and DHA and also vitamins A and D, in amounts that vary from product to product, and it notes that vitamins A and D can be harmful in excessive amounts. [3]So the two products answer different questions. Fish oil is mainly a question about EPA and DHA. Cod liver oil is also a question about how much vitamin A and vitamin D you are getting from all sources. For each oil on its own, see fish oil and cod liver oil.
Documented differences
| Feature | Fish oil | Cod liver oil | Source |
|---|---|---|---|
| Contains EPA and DHA | Yes | Yes | NCCIH [3] |
| Also supplies vitamins A and D | Not described in the source we read | Yes, in amounts that vary by product | NCCIH [3] |
| Pregnancy advice (UK) | The NHS warning we read is about fish liver oil, not fish oil | NHS: avoid fish liver oil unless your GP advises otherwise | NHS [1] |
| Typical EPA or DHA per serving | Varies; read the label | Varies; read the label | Not stated in the sources we read |
Vitamin A and D figures to keep in mind
These are UK NHS figures for the groups named. Other countries set different values, and figures from the NIH Office of Dietary Supplements could not be read (the site blocked our download), so none are quoted.| Nutrient | Group | Figure | Source and year |
|---|---|---|---|
| Vitamin A | Adults 19 to 64, men | 700 micrograms a day needed | NHS, reviewed 2020 [2] |
| Vitamin A | Adults 19 to 64, women | 600 micrograms a day needed | NHS, reviewed 2020 [2] |
| Vitamin A | Adults, food and supplements combined | Do not exceed 1.5 mg (1,500 micrograms) a day | NHS, reviewed 2020 [2] |
| Vitamin D | Children from age 1 and adults | 10 micrograms a day needed | NHS, reviewed 2020 [4] |
| Vitamin D | Adults and children 11 to 17 | Not more than 100 micrograms (4,000 IU) a day | NHS, reviewed 2020 [4] |
| Vitamin D | Children 1 to 10 | Not more than 50 micrograms (2,000 IU) a day | NHS, reviewed 2020 [4] |
The NHS says too much vitamin D over a long period can cause too much calcium to build up in the body (hypercalcaemia). [4] Cod liver oil taken with a multivitamin can add vitamin A and D on top of each other. See cod liver oil: vitamin A and D content.
EPA and DHA amounts
EFSA (European Union) considered 250 mg a day of EPA plus DHA an adequate intake for the maintenance of general cardiovascular health among healthy adults and children (2012). [5] The same EFSA report said the available data were not enough to set an upper limit for these fats, and that supplemental EPA and DHA up to 5 g a day did not raise safety concerns for adults. [5] These are EFSA statements for the EU, not advice for a person. Vitamin A in cod liver oil is the reason a different ceiling applies to it.Head-to-head evidence
Proper evidence not found. We searched PubMed for trials that directly compared fish oil with cod liver oil and found none to read; the NCCIH page and the Cochrane review we read do not compare them either. The large Cochrane review of omega-3 and heart disease covered 86 trials, most using capsules; its abstract describes no cod-liver-oil comparison. [6] Results for one oil should not be carried over to the other.Frequently asked questions
Is cod liver oil the same as fish oil?
No. Both contain EPA and DHA, but cod liver oil also contains vitamins A and D in amounts that vary by product. [3]
Can I take cod liver oil when pregnant?
The NHS advises avoiding fish liver oil supplements in pregnancy or when trying for a baby unless your GP advises otherwise. [1]
Which one has more omega-3?
Not answerable from the sources we read: EPA and DHA amounts vary by product, so compare the Supplement Facts panels.
How much vitamin A is too much?
The NHS advises adults not to exceed 1.5 mg (1,500 micrograms) a day from food and supplements combined. [2] This is UK advice.
Has research compared the two oils head to head?
We found no trial comparing them. Proper evidence not found, after searching PubMed and reading NCCIH and Cochrane.
More details: evidence, limits and cautions
The details behind this page: cautions, limits of the evidence and where sources disagree. Open any note to read it.
Safety first
- Pregnancy or trying for a baby. The NHS says to avoid fish liver oil supplements unless your GP advises otherwise, because they are high in vitamin A (retinol), which can be harmful to an unborn baby. [1]
- Too much vitamin A over many years. The NHS says an average of more than 1.5 mg (1,500 micrograms) a day may affect bones and make fractures more likely when you are older, and it lists fish liver oil among supplements high in vitamin A. [2]
- A child or anyone who swallowed a large amount of a supplement: in the US call Poison Help at 1-800-222-1222, or 911 if the person collapses or cannot breathe. Other countries: Poison Help by country.
- Both oils can interact with medicines and matter before surgery. See medication interactions and fish oil, blood thinners and bleeding risk. Never change a prescribed medicine on your own; ask the prescriber or a pharmacist.