Arctic Cod Liver Oil

With cod liver oil, the real question usually isn't the omega-3. It's the vitamin A and vitamin D that come with it, and what else you take that contains the same two. These are the questions our naturopaths ask in store, and it only takes a few minutes.

A good fit if

• You want omega-3 with a little vitamin A and vitamin D from one bottle rather than three
• Oily fish rarely makes it onto your plate
• You'd rather take a spoonful of liquid than swallow capsules
• You're not currently taking a multivitamin, a vitamin D supplement or another fish oil
• You like the traditional option and you'll read the back of the label rather than guess

Check with us first if

• You're pregnant or thinking about becoming pregnant. Australian labels must warn you not to take vitamin A supplements without talking to your doctor or pharmacist, because vitamin A above 3,000 micrograms retinol equivalents can cause birth defects.
• You're breastfeeding. The same vitamin A question applies, so raise it with your midwife, doctor or pharmacist before you start.
• You already take a multivitamin, a vitamin D supplement or a natural fish oil. Add up the retinol equivalents and vitamin D across everything before you add this.
• A doctor has asked you to watch your vitamin A. The retinol in cod liver oil counts towards the same 3,000 microgram daily limit.
• You take a blood thinner or an antiplatelet medicine. Across 90 randomised trials, omega-3 supplements showed a small but measurable increase in reported bleeding.
• You have surgery or a dental procedure coming up. Tell your surgeon or dentist what you're taking.
• You have heart disease or heart risk factors and are heading above 2 g a day of EPA and DHA. A higher risk of atrial fibrillation (an irregular heart rhythm) has been measured at those doses.
• You're buying it for a child. There are no children's cod liver oil trials behind this page, and children's Adequate Intakes are far smaller than an adult's.
• You take any prescription medicine at all. Check with your doctor, pharmacist or our naturopaths first.

• Cod liver oil liquid, the traditional spoonful. Best known for: The original format, and the one used in the largest cod liver oil trial. Absorption: Cod liver oil was one of the groups in an absorption trial, but no separate figure was reported for it. Typical use: The Norwegian winter trial of 34,601 people used 5 mL a day, which gave 10 micrograms of vitamin D. A spoon is easier to adjust than a capsule if you need less.
• Cod liver oil capsules. Best known for: The same oil without the taste, at a fixed amount per capsule. Absorption: Not measured separately. It's the same oil in a capsule. Typical use: Easier to take daily, harder to take half of. Check the retinol equivalents and vitamin D per capsule, then check what's in anything else you take.
• Flavoured or emulsified cod liver oil. Best known for: Lemon, orange and mint versions made to be swallowed without a chaser. Absorption: Not measured separately. Typical use: A practical answer if the taste is why the bottle sits unopened. The vitamin A and vitamin D limits apply to these exactly as they do to the plain oil.
• Plain fish oil. Best known for: The most widely used source of EPA and DHA, with the biggest body of trial evidence behind it. Absorption: Natural fish body oil is the 100 per cent benchmark every other form is measured against. Typical use: The simpler choice if omega-3 is all you're after, and the usual answer in pregnancy. Natural fish oil is a separate Schedule 1 ingredient, and the same vitamin A conditions apply where retinol claims are made.
• Concentrated fish oil, sold as rTG or as ethyl esters. Best known for: A meaningful EPA and DHA dose without swallowing six capsules. Absorption: Re-esterified triglycerides reached 124 per cent of natural fish oil, and ethyl esters reached 73 per cent. Typical use: The option if a doctor has asked for a set amount of EPA or DHA. Cod liver oil can't be scaled up that far, because you reach the retinol limit first. Ethyl esters carry their own warnings for pregnancy, blood thinners and under-12s.
• Algal oil. Best known for: The only vegan EPA and DHA, grown from microalgae rather than caught. Absorption: There's no study specific to schizochytrium, the algae it's made from, behind this page. Typical use: The simple alternative if you're allergic to fish or eat no animal products. It contains no vitamin A, and most algal products are mostly DHA.

Reference values. There's no recommended intake for cod liver oil itself. The NHMRC sets an Adequate Intake for the long-chain omega-3s in it (EPA, DPA and DHA combined) of 160 mg a day for men and 90 mg for women, rising to 110–115 mg in pregnancy and 140–145 mg while breastfeeding. An Adequate Intake is the amount that keeps most people from falling short, not a dose tested for a particular benefit.

Typical supplemental range. The largest cod liver oil trial used 5 mL a day through a Norwegian winter, which gave 10 micrograms of vitamin D. Capsule and liquid strengths vary a lot here, so don't go by the oil weight on the front. Read the retinol equivalents and the vitamin D on the back. Follow the directions on the product you buy, and use the label to check your totals.

Upper level. There are two firm limits, both in item 1519 of Australia's permitted ingredients list (Schedule 1). Taken by mouth, a daily dose must provide no more than 3,000 micrograms of retinol equivalents and no more than 25 micrograms of vitamin D. The rules also require the label to say, word for word: "The recommended daily amount of vitamin A from all sources is 700 micrograms retinol equivalents for women and 900 micrograms retinol equivalents for men." Those limits apply to the product, not to you, so anything else you take with vitamin A or vitamin D adds to the same total.

Worth knowing. Take it with food. Because you reach the vitamin A limit long before the omega-3 doses used in heart and cholesterol research, cod liver oil isn't the product to choose if a doctor has asked you to take grams of EPA and DHA a day. What you need depends on your age, diet and health, so talk to one of our naturopaths.

Food first, where the diet allows it.

• Oily fish: salmon, sardines, mackerel, herring: the food route to the same two fats, EPA and DHA
• Sea fish generally: 185 g a week matched a 300 mg daily EPA and DHA supplement in a controlled comparison
• Cod liver itself: eaten as a food in parts of northern Europe; here it reaches you as the oil
• Microalgae: where the fish get their omega-3 in the first place
• Walnuts, flaxseed and chia: plant omega-3 as ALA: a different fat, not EPA or DHA
• Per-serve figures: none are quoted: the reference set behind this page holds no verified table

If any of these sound like you, talk to one of our naturopaths or your doctor before you start.

• You're pregnant or thinking about becoming pregnant. A label warning is required, because vitamin A above 3,000 micrograms retinol equivalents can cause birth defects.
• You're breastfeeding. The same vitamin A question applies, so raise it with your midwife, doctor or pharmacist.
• You're allergic to fish. Cod liver oil comes from fish, and no allergen warning is required for item 1519.
• You already take a multivitamin, vitamin D or another fish oil. Add up the retinol and vitamin D across all of them.
• You take blood thinners or antiplatelet medicines. A small increase in reported bleeding was seen across 90 randomised trials.
• You have surgery or dental work planned. Tell your practitioner what you're taking.
• You have diagnosed heart disease and take more than 2 g a day of EPA and DHA. A higher risk of atrial fibrillation (an irregular heartbeat) has been measured at those doses.
• Children. We have no cod liver oil trial in children to go on.
• You notice signs of an allergic reaction, unusual bleeding or an irregular heartbeat. Stop and get medical advice.
• If you take prescription medicines, check with your doctor, pharmacist or our naturopaths before you start.