Cod liver oil vs omega-3: which to take

What is cod liver oil?

Cod liver oil is an oil taken from the livers of cod and sold as a supplement, as a liquid or in soft capsules. It is a fish liver oil, and the NHS says fish store vitamin A in their livers, so these supplements are high in vitamin A (retinol). Alongside EPA and DHA, the omega-3 fats that most fish oils are bought for, it also carries vitamin D. The sections below cover how it compares with other omega-3 supplements, how much you can take and who should avoid it.

Is cod liver oil the same as omega-3?

No, though cod liver oil does contain omega-3. Omega-3 is a family of fats (ALA from plants, EPA and DHA from fish and algae), and cod liver oil is one source of EPA and DHA. Omega-3 is the nutrient and cod liver oil is one product that supplies it, so omega-3 vs cod liver oil compares a group of fats with a single source of them. The difference is where it comes from: a liver oil also brings vitamin A (retinol) and vitamin D. Other omega-3 supplements are made from fish, krill or algae oil and are bought for their EPA and DHA; their labels show any vitamins added.

What's the difference between cod liver oil and omega-3?

The vitamins, and often how much EPA and DHA you get per capsule. In the UK's food composition tables (CoFID), cod liver oil contains about 18,000 µg of vitamin A, 210 µg of vitamin D, 10.8 g of EPA and 8.3 g of DHA per 100 g. In a gram of oil, roughly what a 1,000 mg capsule holds, that's about 180 µg of vitamin A, 2 µg of vitamin D and 190 mg of EPA and DHA. Concentrated fish oils can hold several times as much EPA and DHA per gram: Omacor, a prescription omega-3 medicine, has 840 mg in a 1 g capsule.

For scale, the NHS says adults aged 19 to 64 need 700 µg of vitamin A a day (men) or 600 µg (women), and 10 µg of vitamin D. Many products are made to a set vitamin content, so the per-capsule figures on the label matter more than the averages above.

Cod liver oil vs fish oil

Cod liver oil is a fish liver oil, while the fish oil in the table's middle column is not, and that matters mostly for vitamin A. The NHS says fish liver oils are high in vitamin A. The British Dietetic Association (BDA) advises choosing omega-3 rather than fish liver oil, and keeping your total vitamin A to 1.5 mg a day or less. The BDA also says omega-3 supplements aren't recommended for the general UK population, because the evidence of benefit is inconclusive, and the NHS advises at least 2 portions of fish a week, including 1 of oily fish.

What are the benefits of cod liver oil?

Its nutrients carry authorised health claims, provided a daily dose contains enough of each.

• EPA and DHA contribute to the normal function of the heart, with the effect seen at 250 mg a day.
• DHA contributes to the maintenance of normal brain function and normal vision at 250 mg of DHA a day.
• Vitamin D contributes to the maintenance of normal bones, teeth and muscle function, and to the normal function of the immune system.
• Vitamin A contributes to the maintenance of normal vision and normal skin, to the normal function of the immune system and to normal iron metabolism.

On the CoFID figures, a single 1,000 mg capsule of plain cod liver oil would fall short of 250 mg of EPA and DHA, so check how much a daily dose provides. Claims that cod liver oil or fish oil keeps joints supple or mobile have been assessed and are not authorised in GB. If your joints are painful or stiff, see your GP.

If you take it for vitamin D, check the label. The NHS advises everyone to consider 10 µg of vitamin D a day in autumn and winter, and the amount in cod liver oil products varies; our vitamin D guide explains who needs it all year.

Cod liver oil benefits for men

The benefits are the same for men and women. The claims above are about the nutrients (EPA, DHA, vitamin D and vitamin A), and none of them mentions sex. The differences are in the numbers: the NHS says men aged 19 to 64 need 700 µg of vitamin A a day and women 600 µg, and that older men, like women past the menopause, should keep vitamin A from food and supplements to 1.5 mg a day or less, because more over many years may make bones more likely to fracture. If you're wondering about cod liver oil for a particular men's health concern, ask your GP or pharmacist.

Who should not take cod liver oil?

Anyone pregnant or trying for a baby, and anyone whose vitamin A or D would go over the NHS limits. Check first if you take a blood thinner.

• If you're pregnant or trying for a baby, the NHS says not to take cod liver oil or any supplement containing vitamin A, because too much vitamin A can harm the baby's development.
• If you eat liver or liver pâté once a week, the NHS says not to take any supplement containing vitamin A, including fish liver oil.
• Women past the menopause and older men should keep vitamin A from food and supplements to 1.5 mg a day or less, the NHS advises, because more over many years may make bones more likely to fracture.
• If you already take a multivitamin or a vitamin D supplement, add the vitamin A and D in each product together. Adults shouldn't take more than 100 µg (4,000 IU) of vitamin D a day.
• If you take warfarin or another blood thinner, speak to your GP, pharmacist or anticoagulation clinic first. The UK prescribing information for Omacor says clotting should be checked when it's combined with warfarin.
• If you're allergic to fish, cod liver oil isn't suitable.

Is cod liver oil safe for kids?

Check with a pharmacist, GP or health visitor before giving a child cod liver oil, because it carries vitamins A and D, and children's upper limits for vitamin D are lower than adults'. The NHS advises daily vitamin drops containing vitamins A, C and D for children aged 6 months to 5 years (babies having more than 500 ml of infant formula a day should not be given them). It says one supplement on its own is enough, so it advises against giving cod liver oil on top of vitamin drops. Its vitamin D ceilings are lower for children: no more than 50 µg (2,000 IU) a day for ages 1 to 10, and 25 µg (1,000 IU) a day under 12 months. Follow the dose on a child's product, and note the BDA's advice that children need less omega-3 than adults.

Cod liver oil capsules or tablets: what should you check?

The label, more than the format. Cod liver oil is sold as a liquid and as soft capsules, and what people call cod liver oil tablets are usually capsules. Before you buy, check:

1. the vitamin A per daily dose, in µg
2. the vitamin D per daily dose, in µg or IU (1 µg is 40 IU)
3. the EPA and DHA per daily dose
4. how many capsules or how much liquid makes one dose

If a label gives vitamin A or D in IU, our vitamin unit converter turns it into micrograms so you can add it to your other supplements.

What does high strength cod liver oil mean?

High strength on its own doesn't tell you how much of anything is in a capsule, so read the numbers. A stronger capsule may hold more EPA and DHA, more vitamin A and D, or both, and more vitamin A or D means fewer capsules before you reach the limits in the next section. Compare products on EPA plus DHA per daily dose first, then on vitamin A and D per daily dose, and check the total against the NHS limits that apply to you.

What about malt and cod liver oil?

Malt and cod liver oil is cod liver oil blended with malt extract, so the same vitamin A and D rules apply as for plain cod liver oil. The NHS advice to avoid fish liver oil supplements in pregnancy still stands, and for a child the NHS advice above applies. The vitamin A and D in each spoonful or serving are what count towards your limits, so check the label and add them to your other supplements.

When should you take cod liver oil?

With a meal, at whatever time of day you'll remember. In small studies from the 1980s, EPA from fish oil was absorbed better when taken with a high-fat meal than with a low-fat one. We know of no evidence that morning or evening makes a difference. Take it every day at about the same point, and don't take a second vitamin A or D product on top without checking the totals.

How many cod liver oil capsules can you take a day?

There's no single safe number, because each capsule holds a different amount of vitamin A and D, so follow the label dose and don't go over it. The limits that matter are fixed. The NHS says to keep vitamin A from food and supplements combined to 1.5 mg (1,500 µg) a day or less, and that adults shouldn't take more than 100 µg (4,000 IU) of vitamin D a day. To find your ceiling, take off the vitamin A and D you already get from other supplements and food, then divide what's left by the amount in one capsule. On the CoFID average used earlier, a 1,000 mg capsule holds about 180 µg of vitamin A, so around eight would reach 1.5 mg before you count anything else, which is why the label and your other supplements matter more than the average. If you're pregnant or trying for a baby, the NHS says to avoid fish liver oil supplements unless your GP advises otherwise.

Is there a vegan cod liver oil?

No: cod liver oil comes from fish, so a vegan version doesn't exist. A plant-based alternative covers its three parts separately. For EPA and DHA, look for algae oil: the BDA notes that some omega-3 supplements contain only algae and suit vegetarians and vegans. For vitamin D, a daily 10 µg supplement in autumn and winter is the NHS advice for everyone; check the source if you need it to be vegan. For vitamin A, the body makes it from beta-carotene in foods such as carrots, sweet potatoes, spinach, red peppers, mango and apricots. If you have a fish allergy, the Food Standards Agency warns that a vegan label doesn't rule out cross-contamination, so read the allergen information.

Cod liver oil or omega-3: which should you take?

If you want EPA and DHA, an omega-3 supplement without vitamin A is the simpler choice, and the BDA advises choosing omega-3 over fish liver oil. Cod liver oil can make sense if you also want its vitamin D, you've added up your vitamin A from food and other supplements, and you aren't pregnant or trying to be. If you take both, add up the EPA and DHA as well as the vitamins. Our guide to omega-3 supplements covers how to compare them, and supplements to take together shows how to avoid doubling up.

Where Natura fits

Natura doesn't sell cod liver oil. Daily Omega, in the Natura cabinet (coming soon), is a fish-oil concentrate taken as one softgel a day with food, providing EPA 480 mg and DHA 360 mg plus natural vitamin E 5 mg, and its label data lists no vitamin A or D; Daily D3 (lichen vitamin D3, 10 µg) is a separate bottle, and both are with the daily bottles. If you take cod liver oil, note that Natura's Daily Multi, Daily Vitamin A and Vitamins Pack each contain 800 µg of vitamin A (and Daily Multi has 50 µg of vitamin D3), so adding one of them to cod liver oil could take your vitamin A past 1.5 mg a day.