Home Ingredients Cod Liver Oil
CardiovascularBone Health

Cod Liver Oil

Gadus morhua
Evidence Level
Strong
2 Clinical Trials
5 Documented Benefits
4/5 Evidence Score

Oil extracted from the liver of cod (primarily Atlantic cod, Gadus morhua) — distinguished from regular fish oil by significant vitamin A and vitamin D content (in addition to EPA and DHA). Traditional supplement used for centuries in Northern European populations to prevent rickets and provide omega-3s during winter. Modern cod liver oil concentrations are standardized; some products are vitamin A/D-reduced. Critical safety: significant vitamin A and D content requires careful dose management. Cumulative retinol toxicity risk at chronic high doses (liver damage, paradoxical bone weakening, headaches, hair loss, dry skin). Vitamin A teratogenicity makes cod liver oil controversial in pregnancy — modern US/UK recommendation is to avoid in pregnancy and use fish oil + separate vitamin D instead.

Studied Dose 1 teaspoon (5 mL) typical dose providing ~750-2,500 IU vitamin A, ~400-1,000 IU vitamin D3, ~500-1,000 mg combined EPA+DHA. Check label — vitamin A content varies widely (some traditional products provide 5,000-10,000 IU/tsp, approaching toxicity over months/years). Pregnancy: avoid (vitamin A teratogenicity).
Active Compound EPA + DHA + Vitamin A (retinyl esters) + Vitamin D3 (cholecalciferol)

Benefits

Combined EPA/DHA + vitamin D source

Provides omega-3 EPA and DHA plus vitamin D3 (cholecalciferol) and vitamin A (retinyl esters) in one product. Multi-nutrient profile distinguishes from typical fish oil (which lacks vitamins A and D) and from standalone vitamin D supplements. Particularly relevant for Northern latitude winter supplementation where reduced sun exposure limits endogenous vitamin D synthesis.

Supported by Trial 1

Bone health (vitamin D + EPA/DHA)

Vitamin D supports calcium absorption and bone mineralization; EPA and DHA support bone metabolism via inflammatory pathway modulation. Combined nutrient profile relevant to bone health at multiple mechanisms simultaneously.

Supported by Trial 1, Trial 2

Immune function (vitamin A + vitamin D)

Both vitamin A and vitamin D play essential roles in immune function. Combined deficiency states are particularly relevant in populations with limited dietary diversity or sun exposure.

Supported by Trial 1

Vision support (vitamin A)

Vitamin A (as retinyl esters) supports vision via retinal photopigment regeneration. Cod liver oil traditionally addressed vitamin A deficiency-related vision problems in populations with limited dietary access to retinol.

Supported by Trial 1

Same cardiovascular/inflammation effects as fish oil

EPA and DHA content provides the same cardiovascular and anti-inflammatory effects as fish oil. Per-dose EPA+DHA content is typically lower than concentrated fish oils — cod liver oil is more efficient as a multi-nutrient supplement than as a pure omega-3 source.

Supported by Trial 2, Trial 1

Mechanism of action

1

Vitamin A (retinol) mechanisms

Vitamin A (retinyl esters from fish liver) supports vision (retinal photopigment regeneration), immune function, and epithelial maintenance. Critical caveat: cumulative retinol toxicity risk with chronic high doses; teratogenicity at >10,000 IU/day in pregnancy.

2

Vitamin D3 (cholecalciferol) mechanisms

Vitamin D3 supports calcium absorption, bone mineralization, immune function, and hundreds of vitamin D receptor-mediated downstream effects. Particularly relevant to Northern latitude populations with limited UV exposure for endogenous synthesis.

3

EPA + DHA mechanisms

Same as fish oil: EPA and DHA omega-3 fatty acids modulate inflammatory eicosanoid balance, support cardiovascular function, and contribute to brain and retinal membrane integrity.

4

Synergistic nutrient profile

Combined vitamin A + vitamin D + EPA/DHA in natural ratios as found in cod liver. Particularly relevant to Northern latitude winter contexts (low sun → low endogenous vitamin D; cold weather → potentially reduced fish intake). Modern alternatives (vitamin D + fish oil/algae oil) provide more controllable dosing.

Clinical trials

1
Cod Liver Oil Historical Rickets Prevention

Cod liver oil gained prominence in late 1800s and 1900s for rickets prevention — vitamin D deficiency due to limited sun exposure in northern latitudes. Foundational public health evidence preceding modern RCT methodology.

2
Cod Liver Oil for Joint Health — Galarraga 2008

Galarraga 2008 — rheumatoid arthritis adjunct evidence. Anti-inflammatory benefits relevant to RA management context.

Side effects and drug interactions

Common Potential side effects

GI distress (fishy reflux, burping, nausea) — similar to fish oil.
Fishy aftertaste — strong unless flavored or in capsules.
VITAMIN A TOXICITY at high doses or chronic over-use — most concerning long-term risk.
VITAMIN D toxicity at very high doses (less concerning than vitamin A).
Bleeding risk theoretical at high doses (EPA/DHA mechanism).
Pregnancy concern: HIGH-DOSE VITAMIN A is teratogenic; EXCESS RETINOL >10,000 IU daily in pregnancy associated with birth defects.

Important Drug interactions

VITAMIN A INTERACTIONS — retinoid medications (isotretinoin, tretinoin), other vitamin A supplements; AVOID combining (additive vitamin A toxicity).
ANTICOAGULANTS — additive bleeding risk (EPA/DHA + vitamin A may potentiate warfarin); monitor INR.
VITAMIN D-CONTAINING SUPPLEMENTS — total vitamin D intake matters; cod liver oil + multivitamin + vitamin D supplement may cause excess.
ANTACIDS — modestly affect fat absorption.
Diuretics — hypercalcemia concerns with vitamin D excess.
PREGNANCY — VITAMIN A TERATOGENIC at high doses; cod liver oil during pregnancy CONTROVERSIAL — choose low-vitamin-A products or fish oil instead during pregnancy.
Children — pediatric dosing; check vitamin A and D limits.
Featured In

Symptom-specific supplement guides

🛡️Best Supplements for Immune Support

More Cardiovascular Ingredients

Cardiovascular
Niacin
Niacin, or vitamin B3, is a vital nutrient that supports energy production by serving as a…
Cardiovascular
Omega-3 Fatty Acids
Omega-3 fatty acids, primarily eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), an…
Cardiovascular
Potassium
Potassium is the most abundant intracellular cation in the human body and an essential min…
Cardiovascular
Pycnogenol® (French Maritime Pine Bark)
Pycnogenol® (Horphag Research) is a standardized extract from the bark of French maritime…

Explore Other Ingredients

Antioxidant
NAC (N-Acetylcysteine)
NAC (N-Acetyl Cysteine) is a supplemental form of the amino acid cysteine, best known for…
Antioxidant
Milk Thistle
Milk thistle, derived from the Silybum marianum plant, contains silymarin, a compound know…
Antioxidant
Dandelion Root
Dandelion root is one of the most widely used hepatic and diuretic herbs in Western botani…

Frequently asked questions about Cod Liver Oil

What is Cod Liver Oil?

Oil extracted from the liver of cod (primarily Atlantic cod, Gadus morhua) — distinguished from regular fish oil by significant vitamin A and vitamin D content (in addition to EPA and DHA).

What does Cod Liver Oil do?

Vitamin A (retinyl esters from fish liver) supports vision (retinal photopigment regeneration), immune function, and epithelial maintenance. Critical caveat: cumulative retinol toxicity risk with chronic high doses; teratogenicity at >10,000 IU/day in pregnancy. In clinical research, Cod Liver Oil has been studied for combined epa/dha + vitamin d source, bone health (vitamin d + epa/dha), immune function (vitamin a + vitamin d).

Who should take Cod Liver Oil?

Cod Liver Oil may be most relevant for people interested in cardiovascular, bone health. It has been clinically studied for combined epa/dha + vitamin d source, bone health (vitamin d + epa/dha), immune function (vitamin a + vitamin d). As with any supplement, consult your healthcare provider before starting, especially if you have medical conditions or take prescription medications.

How long does Cod Liver Oil take to work?

Most clinical trial effects appear over weeks of consistent use; individual response varies. Acute or same-day effects (where applicable) typically appear within hours, but most cumulative benefits — particularly those affecting biomarkers, mood, sleep quality, or chronic symptoms — require 4-12 weeks of regular use to fully assess. If you don't notice benefit after 12 weeks at the appropriate dose, it may not be your responder.

When is the best time to take Cod Liver Oil?

For cardiovascular or metabolic goals, Cod Liver Oil is typically taken with meals to support absorption and reduce GI sensitivity. Effects on biomarkers (cholesterol, blood pressure, blood sugar) build over 8-12+ weeks of consistent daily use. Always check product labeling and follow personalized guidance from your healthcare provider.

Is Cod Liver Oil worth taking?

Cod Liver Oil has strong clinical evidence (Evidence Level 4/5 on NutraSmarts) for its primary uses, with multiple randomized controlled trials and meta-analyses supporting its benefits. Whether it's worth taking depends on your specific goals, what you've already tried, your budget, and your overall supplement strategy. The honest framing: no supplement is essential for most people, and lifestyle factors (sleep, exercise, diet, stress management) typically produce larger effects than any single supplement. Cod Liver Oil is most worth trying if its evidence-supported uses align with your specific goals.

What is the recommended dosage of Cod Liver Oil?

The clinically studied dose for Cod Liver Oil is 1 teaspoon (5 mL) typical dose providing ~750-2,500 IU vitamin A, ~400-1,000 IU vitamin D3, ~500-1,000 mg combined EPA+DHA. Check label — vitamin A content varies widely (some traditional products provide 5,000-10,000 IU/tsp, approaching toxicity over months/years). Pregnancy: avoid (vitamin A teratogenicity).. Always follow product labeling and consult a healthcare provider for personalized dosing recommendations.

What is Cod Liver Oil used for?

Cod Liver Oil is studied for combined epa/dha + vitamin d source, bone health (vitamin d + epa/dha), immune function (vitamin a + vitamin d). Provides omega-3 EPA and DHA plus vitamin D3 (cholecalciferol) and vitamin A (retinyl esters) in one product. Multi-nutrient profile distinguishes from typical fish oil (which lacks vitamins A and D) and from standalone vitamin D supplements.