What is Cod Liver Oil?

Cod liver oil comes from the livers of Atlantic cod and has been used as a food and medicine along the Norwegian coast for at least 300 years. Unlike regular fish oil, it delivers not just omega-3 fatty acids but also pre-formed vitamin D3 and vitamin A in meaningful amounts — making it a nutritionally unique all-in-one supplement. It was one of the first treatments recognized by Western medicine for preventing rickets in children, long before vitamins were even named.

How does Cod Liver Oil work?

The omega-3 fats EPA and DHA help reduce the body's inflammatory signals, which is why cod liver oil eases joint pain and supports heart and brain health. The vitamin D it contains helps the body absorb calcium, regulate immune cells, and support mood — functions that are often compromised in people who spend little time in sunlight. Vitamin A supports skin health, vision, and immune defense, rounding out the oil's wide-ranging benefits.

What forms does Cod Liver Oil come in?

Liquid oil is the most potent and cost-effective form and absorbs slightly better with meals. Softgel capsules are more convenient and mask the taste, though you need more capsules to match a spoonful of liquid. Flavored liquids (lemon or mint) are popular for children and taste-sensitive adults. Fermented versions are considered more traditional but are harder to find and more expensive.

Where it comes from:

Norwegian fishermen were rubbing cod liver oil into aching joints and drinking it to ward off winter illness as far back as the 1700s. By the 1800s, European physicians were prescribing it for rickets, tuberculosis, and rheumatism. The British Navy used it to keep sailors healthy during long voyages. When vitamin D was formally identified in the 1920s, scientists confirmed what coastal communities had already known for generations — this oil was genuinely medicinal.

What does Cod Liver Oil help with?

• Joint pain and stiffness (arthritis): The omega-3s in cod liver oil calm the inflammatory signals that drive joint swelling and morning stiffness in conditions like rheumatoid arthritis. Regular use over 8–12 weeks can meaningfully reduce pain and may allow some people to lower their dose of anti-inflammatory medications.
• Vitamin D deficiency: Cod liver oil is one of the few natural food sources of vitamin D3, making it especially valuable for people in northern latitudes, those who work indoors, or anyone with darker skin who struggles to make enough from sunlight. Even a small daily dose can make a real dent in a deficiency.
• Heart disease risk: The EPA and DHA in cod liver oil help lower triglycerides, reduce arterial inflammation, and support healthy blood pressure — all factors that influence cardiovascular risk. It also appears to make blood platelets slightly less 'sticky,' which is part of why omega-3s are so widely recommended for heart health.
• Depression and low mood: Both omega-3 fatty acids and vitamin D independently support brain chemistry involved in mood regulation. People with depression often have lower levels of both, and cod liver oil's combination makes it a practical supplement to consider as part of a broader approach to mental wellbeing.
• Dry eyes and eye health: Omega-3s support the quality of the tear film that keeps eyes moist, and vitamin A is essential for the light-sensing cells in the retina. Cod liver oil's combination of both nutrients makes it particularly useful for people with dry eye syndrome or early concerns about night vision.
• Bone health and osteoporosis prevention: Vitamin D from cod liver oil helps the gut absorb calcium properly — without enough vitamin D, calcium from food largely goes to waste. Vitamin A and omega-3s also play supporting roles in bone remodeling, making cod liver oil a useful complement to calcium supplementation.
• Immune system support: Vitamin D acts as a key regulator of immune cells, helping the body respond appropriately to infections without overreacting. Cod liver oil's historical use for preventing and treating respiratory illness in cold, dark climates aligns well with what we now understand about vitamin D and immune defense.
• Skin health and dryness: Vitamin A supports skin cell renewal and barrier function, while omega-3s help maintain the moisture layer of the skin from the inside out. This combination makes cod liver oil helpful for dry, flaky, or inflammation-prone skin conditions.
• Childhood development and brain health: DHA is a critical building block for the developing brain and nervous system, and vitamin D supports bone growth in children. Cod liver oil has been used for generations to support healthy development in infants and young children, particularly in regions with limited sun exposure.
• High triglycerides: EPA and DHA are among the most well-studied natural compounds for lowering elevated triglyceride levels in the blood. Cod liver oil provides these at meaningful doses and can be a natural first step before considering pharmaceutical options for mildly elevated triglycerides.

What can Cod Liver Oil help prevent?

• Rickets (vitamin D and A deficiency in children)
• Cardiovascular disease: reduces triglycerides and inflammatory markers associated with heart disease risk
• Vitamin D deficiency-related immune suppression
• Age-related bone loss (osteoporosis) when combined with adequate calcium intake

Which foods are rich in Cod Liver Oil?

1. Cod liver (whole): The direct source — eating cooked cod liver delivers the same omega-3s, vitamin D, and vitamin A as the extracted oil, in highly bioavailable form.
2. Atlantic mackerel: One of the highest omega-3 fish available, with meaningful vitamin D content — a strong whole-food alternative for omega-3 and D intake.
3. Wild-caught salmon: Rich in EPA, DHA, and vitamin D3 — wild salmon is the most widely available fatty fish that closely mirrors cod liver oil's omega-3 and vitamin D profile.
4. Sardines (canned in olive oil): Affordable and nutrient-dense, sardines provide a solid dose of omega-3s, vitamin D, and even some vitamin A — often eaten whole with bones for added calcium.
5. Herring: A traditional Northern European fish with high omega-3 and vitamin D content, historically eaten alongside cod liver oil in Scandinavian diets.

Practical Tips:

Cod liver oil's unique nutrient trio (omega-3s + vitamin D3 + vitamin A) is hard to fully replicate through diet alone. Eating fatty fish 2–3 times per week covers the omega-3 piece well, but most people will still need supplemental vitamin D if they don't get regular sun exposure, especially in winter months or northern climates.

What are the side effects of Cod Liver Oil?

• Fishy aftertaste or fishy breath: most common complaint, reduced by taking with meals or choosing flavored/enteric-coated options
• Loose stools, nausea, or digestive discomfort: usually at higher doses or on an empty stomach
• Vitamin A toxicity with chronic overdose: symptoms include headache, dry skin, hair loss, nausea, and in severe cases liver damage
• Vitamin D toxicity (rare at typical doses): possible with prolonged high-dose use alongside other vitamin D supplements
• Increased bleeding time: relevant before surgery or in those on blood thinners
• Oxidized oil (rancidity) if stored improperly: rancid oil may increase oxidative stress rather than reduce it; always refrigerate liquid oil and check for fresh smell

Good to know:

Cod liver oil is safe for most adults and children at standard doses, but the vitamin A content means that more is not always better — long-term high-dose use needs monitoring.

How much Cod Liver Oil should you take?

• Recommended daily: 1 teaspoon (5 ml) of liquid oil daily, providing approximately 1,000–1,200 mg combined EPA/DHA, 400–1,200 IU vitamin D3, and up to 3,000 IU vitamin A. Capsule equivalent: 2–4 standard softgels depending on brand. Do not exceed 1 tablespoon (15 ml) daily without medical supervision due to vitamin A accumulation risk.
• Best time of day: Morning is most popular and works well for consistency. Some people find taking it with breakfast also reduces fishy aftertaste.
• With or without food: Always take with a meal containing some fat — the vitamins A and D in cod liver oil are fat-soluble and absorb significantly better alongside dietary fat. Avoid taking on an empty stomach.
• Time to effect: Vitamin D levels improve within 4–12 weeks. Joint and inflammatory benefits typically noticed at 8–12 weeks. Triglyceride-lowering effects measurable within 6–8 weeks.
• How long to take it: Suitable for year-round daily use at standard doses. Those in low-sunlight climates may particularly benefit from consistent winter supplementation. If taking alongside other vitamin A or D sources, check total intake periodically — a blood test for vitamin D and vitamin A every 6–12 months is sensible for long-term users.