Cod Liver Oil
Also known as: CLO, Gadus morhua liver oil, fermented cod liver oil, Norwegian cod liver oil
Cod liver oil is pressed from the livers of Atlantic cod. It supplies EPA and DHA at lower concentrations than fish body oil concentrates, but unlike those oils it also naturally contains preformed vitamin A (retinol) and vitamin D. That combination is why it has a long history as a traditional daily supplement in northern Europe. Formulators dose it as milligrams of whole oil and must account for the retinol and vitamin D it contributes to a formula. It is commonly used in general wellness, bone, and immune-positioned products.
Research summary
Provides EPA and DHA for membrane and lipid-mediator functions alongside retinol and cholecalciferol, which act through nuclear receptors.
Dosage
Daily amounts, of compound.
| Lowest studied | Typical range | Highest studied | Upper limit |
|---|---|---|---|
| 1,000 mg | 1,000–2,000 mg | 4,600 mg | — |
Dosed as mg whole oil. A large Norwegian RCT used 5 mL/day (about 4,600 mg at roughly 0.92 g/mL), which supplied 10 mcg (400 IU) vitamin D per day; this is used as dose_max_studied. Vitamin A and D content varies widely by grade and whether vitamins are re-added after refining; obtain the mcg retinol and mcg vitamin D per gram from the supplier CoA and count them toward the formula's vitamin A and D totals and their ULs. Take with food.
Standardization: Declare EPA, DHA, vitamin A (mcg RAE), and vitamin D (mcg) per 1,000 mg oil
Source material: Atlantic cod liver, refined and deodorized
As supplied: EPA+DHA typically about 15-25% of oil mass; vitamin A and D content is grade-specific
Forms of Omega-3
| Form | Typical dose | Element % | Formats | Price |
|---|---|---|---|---|
| Cod Liver Oil | 1,000–2,000 mg | — | Softgel, Liquid | mid |
| Fish Oil (EPA/DHA Concentrate) | 500–2,000 mg | — | Softgel, Liquid | mid |
| Krill Oil | 500–2,000 mg | — | Softgel, Liquid | high |
| Algal DHA (Algae Oil) | 200–500 mg | — | Softgel, Liquid | high |
Format suitability
- Capsule
- Powder
- Tablet
- Softgel
- Gummy
- Liquid
Oil-based; softgel or liquid only. Strong flavor; liquids are usually lemon- or mint-flavored. Common softgel sizes 500 mg and 1,000 mg.
Formulation notes
Adds preformed vitamin A; stacking with other retinol sources (multivitamins, liver extracts) can push totals toward the vitamin A UL, which matters in prenatal formulas. Also contributes vitamin D toward any vitamin D total. Fish allergen.
- Allergen: fish
Sources
- Prevention of covid-19 and other acute respiratory infections with cod liver oil supplementation, a low dose vitamin D supplement: quadruple blinded, randomised placebo controlled trial. (Brunvoll 2022)PubMed
- Omega-3 Fatty Acids — Health Professional Fact SheetNIH ODS
- Vitamin A and Carotenoids — Health Professional Fact SheetNIH ODS
Related ingredients
Vitamin D3 (Cholecalciferol)
VitaminThe form of vitamin D the body makes from sunlight and the most effective supplemental form for raising blood levels.
Typical: 1,000–2,000 IU
Vitamin K2 (MK-7)
VitaminMenaquinone-7 is the long-chain vitamin K2 originally isolated from natto and now made by Bacillus fermentation or synthesis.
Typical: 90–200 mcg
Spirulina
OtherSpirulina is a dried cyanobacterium (Arthrospira platensis or A.
Typical: 1–5 g
Vitamin D3 (Vegan, Lichen-Sourced)
VitaminChemically identical cholecalciferol extracted from lichen rather than sheep's wool lanolin, which lets a product carry vegan and vegetarian claims while keeping the D3 form that raises and holds serum 25(OH)D better than D2.
Typical: 1,000–2,000 IU
Vitamin K1 (Phylloquinone)
VitaminPhylloquinone is the plant form of vitamin K found in leafy greens and the main dietary form.
Typical: 90–200 mcg