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Cod Liver Oil
Cod liver oil is essentially fish oil with a built-in multivitamin problem.
- Evidence
- Likely Effective
- Category
- Omega Fatty Acids
- Best form
- liquid (lemon or orange flavored)
- Effective dose
- 1-2 tsp liquid or equivalent capsules daily, providing roughly 1,000-2,000mg combined EPA+DHA plus vitamins A and D
- Lab tested
- 8 of 10 products
- Category
- Omega Fatty Acids
- Best form
- liquid (lemon or orange flavored)
- Effective dose
- 1-2 tsp liquid or equivalent capsules daily, providing roughly 1,000-2,000mg combined EPA+DHA plus vitamins A and D
- Lab tested
- 8 of 10 products
What Is Cod Liver Oil?
Cod liver oil is essentially fish oil with a built-in multivitamin problem. It provides the same EPA and DHA omega-3 fatty acids as standard fish oil - with decades of cardiovascular, anti-inflammatory, and triglyceride-lowering evidence behind them - but it also delivers significant amounts of preformed vitamin A (retinol) and vitamin D3. That combination is both the selling point and the liability.
The omega-3 evidence is strong. Large reviews confirm that EPA and DHA reduce coronary heart disease events and mortality. Omega-3 supplementation at 2-4g/day reliably lowers triglycerides by 15-30%. These benefits apply to cod liver oil insofar as it delivers adequate EPA and DHA, though most products provide lower omega-3 per serving than concentrated fish oil.
For rheumatoid arthritis specifically, a 2002 study by Gruenwald et al. and a Cochrane review by Goldberg and Katz (2007) found that omega-3 supplementation reduces joint tenderness and NSAID use. Cod liver oil was historically the most common delivery vehicle for this purpose in Northern Europe.
The vitamin D angle has historical significance. Before supplementation was widely available, cod liver oil was the primary defense against rickets in northern latitudes. A teaspoon of cod liver oil typically provides 400-1,000 IU of vitamin D3. This is meaningful but unremarkable - a standalone vitamin D3 supplement costs pennies per day and lets you dose precisely.
Here is the honest assessment: for most people, cod liver oil is an inferior choice compared to taking fish oil plus separate vitamin D3. The reason is simple - you cannot independently adjust your omega-3 and vitamin A/D doses. If you need 2,000mg of EPA+DHA daily, the amount of cod liver oil required to reach that dose may push your vitamin A intake uncomfortably close to the tolerable upper limit of 3,000mcg RAE/day, especially if you are also eating liver, fortified foods, or taking a multivitamin with vitamin A. Vitamin A toxicity is a real concern, not a theoretical one - it causes liver damage, bone loss, and birth defects.
Cod liver oil makes the most sense for people who want a simple all-in-one supplement providing moderate omega-3s plus vitamins A and D, who are not taking other vitamin A sources, and who do not need high-dose omega-3 therapy.
Does It Work? The Evidence
Cardiovascular health and triglyceride reduction
SupportedCochrane review 2019 (86 RCTs, n=162,796); REDUCE-IT trial (NEJM 2019, n=8,179); PMID 30525132
Anti-inflammatory effects and rheumatoid arthritis
SupportedGoldberg & Katz Cochrane review 2007; Gruenwald et al. 2002; PMID 17335973
Vitamin D provision (bone health, immune function)
SupportedHistorical use against rickets; Martineau et al. BMJ 2017 meta-analysis (for vitamin D broadly); PMID 28202713
Vitamin A provision (vision, immune function)
Early SignalNIH ODS Vitamin A Fact Sheet; relevant mainly in populations with inadequate dietary vitamin A intake
Cognitive health and brain development
Early SignalDHA is a structural component of brain tissue; observational data from Nurk et al. 2007; PMID 17092830
Depression and mood improvement
ConflictedLiao et al. 2019 meta-analysis of omega-3 for depression (modest effect); PMID 31480076
| Claimed Benefit | Key Studies | Our Verdict |
|---|---|---|
| Cardiovascular health and triglyceride reduction | Cochrane review 2019 (86 RCTs, n=162,796); REDUCE-IT trial (NEJM 2019, n=8,179); PMID 30525132 | Supported |
| Anti-inflammatory effects and rheumatoid arthritis | Goldberg & Katz Cochrane review 2007; Gruenwald et al. 2002; PMID 17335973 | Supported |
| Vitamin D provision (bone health, immune function) | Historical use against rickets; Martineau et al. BMJ 2017 meta-analysis (for vitamin D broadly); PMID 28202713 | Supported |
| Vitamin A provision (vision, immune function) | NIH ODS Vitamin A Fact Sheet; relevant mainly in populations with inadequate dietary vitamin A intake | Early Signal |
| Cognitive health and brain development | DHA is a structural component of brain tissue; observational data from Nurk et al. 2007; PMID 17092830 | Early Signal |
| Depression and mood improvement | Liao et al. 2019 meta-analysis of omega-3 for depression (modest effect); PMID 31480076 | Conflicted |
How to Choose: Forms, Doses & What Matters
Clinical dose: 1-2 tsp liquid or equivalent capsules daily, providing roughly 1,000-2,000mg combined EPA+DHA plus vitamins A and D
Best forms: liquid (lemon or orange flavored), softgel capsules, extra virgin (minimally processed)
Take with a meal containing fat for optimal absorption of both the omega-3s and the fat-soluble vitamins A and D. Liquid cod liver oil can be taken straight or mixed into smoothies - flavored versions (lemon, orange) are far more palatable than unflavored. Keep liquid cod liver oil refrigerated after opening and use within 2-3 months, as omega-3s are susceptible to oxidation. If using capsules, standard servings are typically 2-4 softgels. Morning or midday dosing is fine. Do not exceed the recommended dose on the label - unlike fish oil, more is not better here because of the vitamin A ceiling. Always check the vitamin A content per serving and add it to your total daily intake from all sources.
Who Should Take Cod Liver Oil?
People who want a simple all-in-one supplement providing moderate omega-3 fatty acids plus vitamins A and D in a single product. Particularly relevant for those in northern latitudes with limited sun exposure who are not taking a separate vitamin D supplement or multivitamin. May be a good fit for older adults with low dietary intake of both omega-3s and fat-soluble vitamins, and for those who prefer a traditional whole-food supplement over isolated nutrients. Historically used and studied in rheumatoid arthritis patients for its anti-inflammatory omega-3 content.
Who Should Avoid It?
Anyone already taking a multivitamin containing vitamin A (retinol/retinyl palmitate) - the combined vitamin A intake can approach or exceed the tolerable upper limit of 3,000mcg RAE/day, risking liver toxicity and bone loss. Pregnant women must be especially cautious: excess preformed vitamin A (above 3,000mcg RAE/day) is teratogenic and causes birth defects. People on blood thinners (warfarin, aspirin) should consult their physician, as omega-3s have mild anticoagulant effects. Those with fish or shellfish allergies should avoid it. People who need high-dose omega-3 therapy (2,000-4,000mg EPA+DHA for triglyceride reduction) should use concentrated fish oil instead, because reaching that dose with cod liver oil would deliver excessive vitamin A.
Side Effects & Safety
Common: fishy aftertaste, fishy burps (less common with flavored liquids or enteric-coated capsules), mild nausea or stomach upset if taken on an empty stomach. These are generally mild and resolve with food. The serious concern is vitamin A accumulation with chronic high-dose use. Preformed vitamin A (retinol) is stored in the liver and can cause hypervitaminosis A at sustained intakes above 3,000mcg RAE/day - symptoms include headache, nausea, liver damage, dry/peeling skin, joint pain, and in severe cases, liver failure. This risk is unique to cod liver oil among omega-3 supplements and is the primary reason most practitioners prefer standard fish oil for high-dose omega-3 supplementation.
Product Scores
10 products scored on dosing accuracy, third-party testing, cost per effective dose, and label transparency.
The Scorecard: 10 Products Compared
Nordic Naturals Arctic Cod Liver Oil (Lemon)
Nordic NaturalsThe benchmark cod liver oil. Excellent purity testing, pleasant lemon flavor, and transparent labeling. The standard other CLO products are measured against.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Carlson Cod Liver Oil (Lemon)
CarlsonExcellent omega-3 content per serving with slightly better pricing than Nordic Naturals. The vitamin A content (850mcg RAE) per tsp is moderate and manageable for most adults.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Nordic Naturals Arctic CLO Softgels
Nordic NaturalsConvenient capsule format from a trusted brand, but you sacrifice dose efficiency versus the liquid version. Pay more per mg of omega-3. Best for people who cannot tolerate liquid CLO.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Garden of Life RAW Cod Liver Oil (Lemon)
Garden of LifeAdded vitamin K2 is a nice touch for bone health. However, uses pollock liver oil rather than true cod liver oil. Good product, slightly misleading name.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
NOW Foods Cod Liver Oil 1,000mg Softgels
NOW FoodsBudget-friendly but significantly underdosed at the label serving size. You are paying for convenience, not clinical efficacy. If you want a NOW omega-3 product, their concentrated fish oil is a better choice.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Dropi Pure Icelandic Cod Liver Oil
Dropi
Icelandic-sourced with minimal processing. A quality product, but the price premium over Nordic Naturals or Carlson is hard to justify given lower omega-3 content and fewer third-party certifications.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Rosita Extra Virgin Cod Liver Oil (EVCLO)
Rosita
The 'artisanal' cod liver oil. Truly minimal processing and high quality, but the price is 3-4x higher than Nordic Naturals or Carlson for lower omega-3 content per serving. A luxury product.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Solgar Norwegian Cod Liver Oil Softgels
SolgarA legacy brand with decent quality but an outdated softgel format that delivers inadequate omega-3 per capsule. Newer concentrated CLO products have made this approach obsolete.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Nature Made Cod Liver Oil 1,000mg Softgels
Nature MadeA trusted brand selling a fundamentally underdosed product. At label serving, you get trivial omega-3 amounts. Scaling up to clinical doses means taking 3-4 capsules and risking excessive vitamin A intake. Nature Made's regular fish oil softgels are a better choice.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Green Pasture Blue Ice Fermented Cod Liver Oil
Green Pasture
This product illustrates why third-party testing matters. Independent analysis found rancidity markers, inconsistent nutrient levels, and quality concerns that contradicted label claims. The 'fermented' angle lacks scientific support. We cannot recommend it.
Prices checked 2026-04-01. Cost shown is per clinically effective daily dose, not per pill.
Full Comparison
| Category | Nordic Naturals Arctic Cod Liver Oil (Lemon) Nordic Naturals | Carlson Cod Liver Oil (Lemon) Carlson | Nordic Naturals Arctic CLO Softgels Nordic Naturals | Garden of Life RAW Cod Liver Oil (Lemon) Garden of Life | NOW Foods Cod Liver Oil 1,000mg Softgels NOW Foods | Dropi Pure Icelandic Cod Liver Oil Dropi | Rosita Extra Virgin Cod Liver Oil (EVCLO) Rosita | Solgar Norwegian Cod Liver Oil Softgels Solgar | Nature Made Cod Liver Oil 1,000mg Softgels Nature Made | Green Pasture Blue Ice Fermented Cod Liver Oil Green Pasture |
|---|---|---|---|---|---|---|---|---|---|---|
| Brand Score | 93/100Winner | 91/100 | 84/100 | 83/100 | 74/100 | 73/100 | 73/100 | 67/100 | 64/100 | 41/100 |
| Dosing & Form | 25/25Winner | 25/25 | 22/25 | 22/25 | 14/25 | 18/25 | 18/25 | 14/25 | 14/25 | 18/25 |
| Purity | 25/25Winner | 23/25 | 23/25 | 20/25 | 19/25 | 20/25 | 23/25 | 19/25 | 20/25 | 7/25 |
| Value | 20/25 | 20/25 | 17/25 | 19/25 | 22/25Winner | 15/25 | 9/25 | 17/25 | 13/25 | 7/25 |
| Transparency | 23/25Winner | 23/25 | 22/25 | 22/25 | 19/25 | 20/25 | 23/25 | 17/25 | 17/25 | 9/25 |
| Cost/Day | $0.49 | $0.43 | $0.73 | $0.59 | $0.24Winner | $0.80 | $1.63 | $0.53 | $0.41 | $1.50 |
| Dose/Serving | 1060mg EPA+DHA | 1100mg EPA+DHA | 750mg EPA+DHA | 850mg EPA+DHA | 300mg EPA+DHA | 700mg EPA+DHA | 600mg EPA+DHA | 350mg EPA+DHA | 300mg EPA+DHA | 500mg EPA+DHA |
| Form | triglyceride-form liquid, lemon flavored | triglyceride-form liquid, lemon flavored | triglyceride-form softgel capsules | liquid, lemon flavored, with added D3 and K2 | softgel capsules, molecularly distilled | extra virgin liquid, cold-processed, unflavored | extra virgin liquid, unrefined, unflavored | softgel capsules | softgel capsules | fermented liquid or capsules |
| Third-Party Tested | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | ✓ Yes | No | ✓ Yes | No |
| Proprietary Blend | No | No | No | No | No | No | No | No | No | No |
Frequently Asked Questions
What is the difference between cod liver oil and regular fish oil?
Both provide EPA and DHA omega-3 fatty acids, but cod liver oil is extracted specifically from cod livers, which are rich in stored vitamins A and D. Regular fish oil is typically extracted from the body tissues of fatty fish (anchovies, sardines, mackerel) and contains little to no vitamin A or D. Fish oil generally provides higher concentrations of EPA and DHA per serving. The trade-off: cod liver oil gives you a multi-nutrient package but limits how much omega-3 you can take before vitamin A becomes a concern.
Can I take cod liver oil and a multivitamin together?
You need to check the vitamin A content carefully. Most multivitamins contain 700-900mcg RAE of preformed vitamin A. A tablespoon of cod liver oil can add another 1,000-4,500mcg RAE depending on the brand. The tolerable upper limit for adults is 3,000mcg RAE/day. If the combined total from your multivitamin, cod liver oil, and diet exceeds that, you risk vitamin A toxicity over time. Either choose a multivitamin without preformed vitamin A (one that uses beta-carotene instead) or switch to regular fish oil.
Is fermented cod liver oil better than regular cod liver oil?
This is controversial. Fermented cod liver oil (most notably from Green Pasture) was marketed as a traditional, minimally processed alternative. However, in 2015, independent testing by Dr. Daniel found significant quality concerns with Green Pasture's product, including rancidity markers and inconsistent nutrient levels. The fermentation process has no proven benefit over standard molecular distillation for cod liver oil. Most experts and third-party testing organizations recommend conventionally processed cod liver oil from established brands with verifiable third-party testing.
Is cod liver oil safe during pregnancy?
This requires careful attention. Omega-3 DHA is beneficial during pregnancy for fetal brain development, and moderate vitamin D is helpful. However, preformed vitamin A above 3,000mcg RAE/day is teratogenic - it causes birth defects. Some cod liver oil products contain enough vitamin A per serving that a double dose or combination with a prenatal vitamin could approach this limit. Most OB-GYNs recommend a prenatal DHA supplement (from fish oil or algal oil) rather than cod liver oil specifically because it avoids the vitamin A risk entirely.
How should I store cod liver oil?
Liquid cod liver oil should be refrigerated after opening and used within 90 days. Omega-3 fatty acids oxidize when exposed to heat, light, and air, producing harmful lipid peroxides and a rancid taste. Store capsules in a cool, dry place away from direct sunlight. Never use cod liver oil that smells strongly fishy or off - that is a sign of oxidation. High-quality products use nitrogen flushing and antioxidants (vitamin E/tocopherols) to slow oxidation.
How much vitamin A is too much from cod liver oil?
The tolerable upper intake level for preformed vitamin A (retinol) in adults is 3,000mcg RAE/day (10,000 IU). A single tablespoon of cod liver oil typically provides 1,000-4,500mcg RAE depending on the brand. If you eat liver, dairy, eggs, and fortified foods, you may already be getting 500-1,000mcg RAE from diet alone. Do the math for your specific product and total dietary intake. Chronic intake above the upper limit causes liver damage, bone loss, and other toxicity symptoms. This is the main reason to be precise about dosing with cod liver oil.
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Sources
- Abdelhamid AS, et al. Omega-3 fatty acids for the primary and secondary prevention of cardiovascular disease. Cochrane Database Syst Rev. 2020;3(3):CD003177.
- Bhatt DL, et al. Cardiovascular Risk Reduction with Icosapent Ethyl for Hypertriglyceridemia (REDUCE-IT). N Engl J Med. 2019;380(1):11-22.
- Goldberg RJ, Katz J. A meta-analysis of the analgesic effects of omega-3 polyunsaturated fatty acid supplementation for inflammatory joint pain. Pain. 2007;129(1-2):210-223.
- Gruenwald J, Graubaum HJ, Harde A. Effect of cod liver oil on symptoms of rheumatoid arthritis. Adv Ther. 2002;19(2):101-107.
- NIH Office of Dietary Supplements. Omega-3 Fatty Acids Fact Sheet for Health Professionals. Updated 2023.
- NIH Office of Dietary Supplements. Vitamin A and Carotenoids Fact Sheet for Health Professionals. Updated 2023.
- Liao Y, et al. Efficacy of omega-3 PUFAs in depression: A meta-analysis. Transl Psychiatry. 2019;9(1):190.
- Nurk E, et al. Cognitive performance among the elderly and dietary fish intake: the Hordaland Health Study. Am J Clin Nutr. 2007;86(5):1470-1478.
FDA Disclaimer: These statements have not been evaluated by the Food and Drug Administration. The products discussed on this page are not intended to diagnose, treat, cure, or prevent any disease. Always consult with a qualified healthcare professional before starting any supplement regimen.