Cod liver oil: benefits, vitamins A and D, and safe amounts

Author: Adrianna Kalista

Adrianna Kalista

Passionate about writing and a graduate in clinical dietetics. She is particularly interested in phytotherapy and the effects of ketogenic nutrition on cognitive brain function.

Verification: Dr. Andreia Torres

Dr. Andreia Torres

Clinical nutritionist with a doctorate in health education. International expert in ketogenic nutrition.

What is cod liver oil?

What is cod liver oil? Cod liver oil is an oil made from cod liver that contains EPA and DHA plus vitamins A and D. Fish oil from whole fish and algae oil do not contain those vitamins A and D [3]. EPA and DHA themselves are made by microalgae and other marine microorganisms at the base of the marine food chain, and cod get them mainly from their diet [1].

Cod liver oil sits in the wider family of omega-3 sources, but it is not simply the same thing as fish oil. The full cod liver oil versus fish oil comparison is covered on its own page, because the vitamin A and D content changes the dosing question.

What are the benefits of cod liver oil?

What are the benefits of cod liver oil? The benefits of cod liver oil come from four nutrients: EPA, DHA, vitamin A and vitamin D. “EPA and DHA contribute to the normal function of the heart” at 250 mg EPA and DHA a day [14]. “DHA contributes to maintenance of normal brain function” at 250 mg DHA a day [14]. “DHA contributes to the maintenance of normal vision” at 250 mg DHA a day [14].

For vitamin D, the authorised wording is “Vitamin D contributes to the maintenance of normal bones” and “Vitamin D contributes to the normal function of the immune system”. For vitamin A, it is “Vitamin A contributes to the maintenance of normal vision” and “Vitamin A contributes to the maintenance of normal skin”. Vitamin claims apply only if the label shows at least a source of that vitamin.

Which cod liver oil is best: capsules, tablets or liquid?

Which cod liver oil is best: capsules, tablets or liquid? The best cod liver oil is the one whose label shows EPA, DHA, vitamin A and vitamin D per daily serving. “1000 mg” usually means the weight of oil, not the amount of EPA, DHA or vitamins.

In one study simulating consumer use, bottled omega-3 oils oxidised faster than capsules: liquid products reached a peroxide value of up to 44.6 meq/kg, compared with up to 7.6 meq/kg for capsules [5]. The GOED voluntary industry monograph is not law and sets maximums of peroxide value 5 meq/kg, p-AV 20 and TOTOX 26 together [4]. Capsules suit people who dislike the taste, while liquid makes it easier to adjust the dose; our omega-3 fish oil guide covers forms in more detail. Check that vitamin A per serving leaves room within EFSA’s adult upper limit of 3 000 µg RE a day [3].

Cod liver oil benefits for men and women: what is different?

Cod liver oil benefits for men and women are covered by the same authorised claims; the difference is safety. The NHS advises avoiding fish liver oil supplements such as cod liver oil during pregnancy or when trying for a baby, because they are high in vitamin A, also called retinol [11].

For oily fish, the NHS sets a limit of no more than 2 portions a week for girls and women who may become pregnant, because pollutants can build up in the body [11]. The NHS gives up to 4 portions a week for boys, while SACN gives up to 4 portions a week for men [11][12]. Those are oily fish limits, not supplement dosing rules.

How much cod liver oil per day is safe?

How much cod liver oil per day is safe depends mainly on vitamin A, but omega-3 cautions still matter. Count the vitamins A and D from cod liver oil, any multivitamin and fortified foods, and stay under EFSA’s adult upper limits of 3 000 µg RE vitamin A and 100 µg vitamin D a day [3]. Combining cod liver oil with a multivitamin is a common way to double up on vitamin A.

For omega-3, SACN’s UK population guideline is 450 mg long-chain omega-3 a day; our how much omega-3 per day guide explains that figure in context [12]. If the aim is vitamin D alone, a separate vitamin D supplement from the keto vitamins range avoids extra vitamin A.

Vitamin A and D upper limits are all-source ceilings, not targets; for EPA and DHA, the 5000 mg line is a supplement safety assessment, not an upper limit or target [3].

Prefer to choose each vitamin yourself?

Separate vitamins let you see the amount of each one on its own label. Browse vitamin D3 drops and other keto vitamins in the BeKeto shop.

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What are the side effects of cod liver oil, and who should avoid it?

What are the side effects of cod liver oil, and who should avoid it? The side effects of cod liver oil come from two areas: vitamin A and omega-3. Too much vitamin A is the reason the NHS advises avoiding fish liver oils in pregnancy and when trying for a baby [11].

Omega-3 did not significantly increase bleeding in 11 trials with 120 643 people, with a rate ratio of 1.09 [9]. The risk of atrial fibrillation rose with dose in 8 large trials with 83 112 people, mainly in people with heart disease or at high risk: about 12% at up to 1 g a day and about 51% above 1 g [8]. People taking anticoagulants or due to have surgery should ask their doctor; see our guide to omega-3 side effects.

Cod liver oil or algae oil: which suits keto better?

Cod liver oil or algae oil: which suits keto better? Cod liver oil and algae oil both give EPA and DHA, but only cod liver oil adds vitamins A and D, and only algae oil is fish-free. Cod liver oil contains vitamins A and D as well as EPA and DHA, while algal oil does not [3]. BeKeto MEGA Omega 3 Vegan Algae Oil Lemon is made from Schizochytrium microalgae, fish-free, vegan and supplied in a dark glass bottle [13]. Malt and cod liver oil products contain malt extract, a sugar syrup, so on keto choose plain oil.

Verdict: BeKeto MEGA Omega 3 Vegan Algae Oil comes out best when you want omega-3 without stacking vitamin A, because one 5 ml teaspoon gives 570 mg DHA and 185 mg EPA, which is 755 mg of EPA and DHA combined [13]. That is above SACN’s 450 mg long-chain omega-3 a day [12]. In a randomised double-blind trial in 74 adults over 6 and 14 weeks, run by an algal oil producer, microalgal oil raised blood EPA and DHA as effectively as fish oil [2]. “This product is intended for adults. Not for use by children or by women who are pregnant or breastfeeding. If you take anticoagulant medication or are due to have surgery, consult your doctor before use.” [13]

For fish-free diets, see our vegan omega-3 guide. You can also include algae oil with other keto supplements when building a simple routine.

Looking for an oil without fish liver?

MEGA Omega 3 Vegan is a lemon-flavoured algae oil made without fish. One 5 ml teaspoon provides 570 mg DHA and 185 mg EPA; it contains no vitamins A or D.

£25.90

Buy MEGA Omega 3

This product is intended for adults. Not for use by children or by women who are pregnant or breastfeeding. If you take anticoagulant medication or are due to have surgery, consult your doctor before use.

Is cod liver oil the same as omega-3?

Is cod liver oil the same as omega-3? Cod liver oil is one source of omega-3 that also carries vitamins A and D [3]. The full cod liver oil vs omega-3 comparison covers fish oil, algae oil and the dosing difference in more detail.

What does the evidence say about omega-3 benefits?

What does the evidence say about omega-3 benefits? Heart effects of EPA and DHA are small and dose-dependent: across 40 trials with 135,267 people, heart attack risk fell about 13% and coronary death about 9%, while total cardiovascular events were not significantly reduced; doses were from 1 g upwards, in a meta-analysis funded by GOED, the omega-3 industry body, whose lead author works for GOED [7]. For the wider picture, read our guide to omega-3 benefits.

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