Algae Omega-3 vs Fish Oil, Cod Liver Oil and Krill: Which Source?

Algal oil, fish oil, cod liver oil and krill oil all supply the same two omega-3 molecules, EPA and DHA, and the body cannot tell where they came from: algal DHA raised blood DHA as much as the same amount from cooked salmon in a direct comparison, because fish get their DHA from algae. What differs: milligrams per serving, chemical form, vitamin A (cod liver oil, which the NHS says to avoid in pregnancy), allergen, oxidation, cost and where it was fished or grown. Flaxseed oil is the odd one out: ALA, the plant omega-3, and no EPA or DHA.^{1, 2}

• Same molecules: algal DHA is bioequivalent to fish DHA
• The differences: mg EPA+DHA per serving, vitamin A (cod liver oil only), fish or shellfish allergen, oxidation, cost, sustainability
• The yardsticks: 250 mg EPA+DHA, 250 mg DHA, 200 mg extra DHA in pregnancy, 2 g ALA

Fish oil, cod liver oil, krill oil, algal oil and flaxseed oil: what each supplies

Typical figures for a 1,000 mg capsule; the label is the authority.

Is algae omega-3 as good as fish oil? (the equivalence trials)

For DHA, yes. In 32 adults given 600 mg of DHA a day for two weeks from algal-oil capsules or cooked salmon, plasma phospholipid DHA rose about 80% and red-cell DHA about 25% in both groups: nutritionally equivalent, in the authors' words.¹ A systematic review found algal DHA raised blood DHA and the omega-3 index in vegetarians and vegans in every study, and in 165 long-term vegans 254 mg a day for four months lifted the index from 3.1% to 4.8% in those below 4%.^{3, 4}

Does algae oil contain EPA?

Some does. The first algal oils were DHA-rich with little EPA, which is where "algae has little or no EPA" comes from; newer strains supply both, typically 150 to 300 mg of EPA. The equivalence trials used DHA-only oils.

Cod liver oil vs fish oil: what is the difference?

Vitamin A, and less omega-3. Fish oil comes from the flesh of oily fish; cod liver oil from the liver, where fish store vitamins A and D, so a capsule carries roughly 200 mg of EPA and DHA plus retinol that fish body oil, algal oil and flaxseed oil do not have.⁵ The NHS says to avoid fish liver oil supplements when pregnant or trying for a baby, and to keep total vitamin A from food and supplements under 1.5 mg a day, so add up liver, multivitamins and cod liver oil.^{5, 6} Cod liver oil plus a fish oil capsule is fine for the omega-3, which simply adds; count the vitamin A. "Vitamin A toxicity" is cod liver oil arithmetic, not an omega-3 side effect.

Krill oil vs fish oil: is krill better absorbed?

A little, perhaps, and it does not change the arithmetic. Krill's EPA and DHA are mainly phospholipids, said to absorb better. In 113 adults over seven weeks, 3 g of krill oil (543 mg EPA+DHA) and 1.8 g of fish oil (864 mg) produced similar rises in plasma EPA and DHA and no differences in lipids: comparable sources, the authors said, at 63% of the dose.⁷ Across seven small trials and 662 people, krill oil lowered triglycerides by about 0.16 mmol/L and LDL cholesterol by about 0.4 mmol/L.⁸ A krill capsule holds perhaps half the EPA and DHA of a standard fish oil capsule, so "better absorbed" is settled by reading both labels.

Where does flaxseed oil fit?

As the ALA source, a different job. ALA is the strictly essential omega-3; the body turns roughly 5% of it into EPA and under 0.5% into DHA, so flaxseed raises blood EPA a little and DHA not at all.² Its register wording is its own: ALA contributes to the maintenance of normal blood cholesterol levels at 2 g a day, which two tablespoons of ground flaxseed or a tablespoon of the oil supply.⁹ Wellgard Vegan Omega 3 6 9 is a flaxseed-oil capsule supplying 692 mg of ALA per two capsules against that 2 g, with 152 mg each of linoleic (omega-6) and oleic (omega-9) acid in flaxseed's own proportions and 10 mg of vitamin E, which contributes to the protection of cells from oxidative stress; it contains no EPA or DHA, which come from oily fish or algal oil.

How to read an omega-3 label (mg EPA and DHA, not mg oil)

Turn it over. "1,000 mg fish oil" is the weight of the oil; a standard capsule is about 18% EPA and 12% DHA, so about 300 mg of omega-3, and "500 mg algae oil" tells you nothing until you find the DHA line. Set the back-of-pack figures against the register's thresholds: 250 mg of EPA and DHA a day for the heart wording, 250 mg of DHA for brain and vision, 200 mg more DHA in pregnancy; SACN's food guideline is 450 mg a day.^{9, 10} Then stop: in the large trials the risk of new atrial fibrillation rose by about half above 1 g a day and about 12% at 1 g or less, so more is not better, and EFSA's 5 g a day is a ceiling, not a target.^{11, 12} Form: re-esterified triglyceride absorbed about a quarter better than natural fish oil and ethyl ester about a quarter worse; all absorb better with a meal containing fat.¹³ Freshness: surveys have found many products over the voluntary oxidation limits (peroxide value 5, anisidine 20, TOTOX 26), and a strong fishy smell means an old oil.^{14, 15} How much omega 3-6-9 do I need daily has worked examples.

Omega-3 gummies vs capsules: what each supplies

A softgel can hold 250 to 500 mg of EPA and DHA; a gummy holds much less oil, so its DHA figure is smaller. Wellgard Vegan Omega 3 Gummies supply 50 mg of algal DHA and 50 mg of ALA per two gummies, against the 250 mg of DHA at which the brain and vision wording applies, with vitamin D3 at 100% of the NRV, which contributes to the maintenance of normal bones and teeth, and vitamins A, C and E: preformed vegan DHA in a gelatine-free chew for a household that will not swallow a capsule or eat fish, with its vitamin A (320 µg a serving, well inside the 1.5 mg ceiling) counted with other retinol sources and the jar kept out of children's reach. Pick by the DHA line and by what you will still be taking in March.

Who should choose which source?

• You eat oily fish most weeks: food supplies the SACN figure; any supplement is a top-up.¹⁰
• No fish, or vegan: algal oil for DHA (and EPA if the label has it), with ALA from flaxseed, chia and walnuts.^{1, 3}
• Pregnant, breastfeeding or trying: fish body oil or algal oil, not cod liver oil, with 200 mg extra DHA as the yardstick and no more than two portions of oily fish a week.^{5, 9}
• Fish allergy: algal oil; shellfish allergy: not krill.

What are the signs you need omega-3 covers who is likely to be low; the Wellgard omega-3 guide the whole subject. Why is fish oil no longer recommended covers the dose question for fish oils.

Frequently asked questions

Is algae omega-3 safe? Who should not take algae oil?

Algal DHA at 200 mg to 1 g a day in trials showed nothing beyond the mild digestive effects fish oil shares; the usual cautions apply: tell your GP or anticoagulant clinic if you take an anticoagulant, and ask a cardiologist before exceeding 1 g a day with a heart rhythm condition.^{1, 3, 11} Is there any danger when taking omega-3 has the bleeding evidence.

What are the side effects of algae omega-3?

The same as fish oil at the same dose: an aftertaste, belching and loose stools, commoner with an oxidised oil and eased by taking it with a meal.

Can I take algae oil every day?

Yes; every trial dosed daily for weeks to months, and daily intake is what keeps the index up.^{3, 4}

What are the cons of krill oil?

Less EPA and DHA per capsule, a higher price per milligram, a shellfish allergen, no outcome trials and a debated fishery; the cholesterol effect in seven small trials has no outcome data behind it.^{7, 8}

Should krill oil be taken at night or morning, and what should you not mix it with?

With a meal, morning or night; time of day has no evidence either way.¹³ Vitamin D and krill oil go together. Tell your clinic if you take an anticoagulant and keep the dose steady.¹ When to take omega-3, 6 and 9 covers timing.

Sources

1. Arterburn LM. Algal-oil capsules and cooked salmon: nutritionally equivalent sources of DHA. 2008. PubMed 18589030.
2. Plourde M, Cunnane SC. Extremely limited synthesis of long chain polyunsaturates in adults. 2007. PubMed 17622276.
3. Craddock JC. Algal supplementation of vegetarian eating patterns improves DHA and omega-3 indices: a systematic review. 2017. PubMed 28417511.
4. Sarter B. Blood DHA and EPA in vegans and effects of an algal-derived omega-3 supplement. 2015. PubMed 24679552.
5. NHS. Fish and shellfish. nhs.uk.
6. NHS. Vitamin A. nhs.uk.
7. Ulven SM. Metabolic effects of krill oil are essentially similar to those of fish oil but at lower dose of EPA and DHA. 2011. PubMed 21042875.
8. Ursoniu S. Lipid-modifying effects of krill oil in humans: systematic review and meta-analysis. 2017. PubMed 28371906.
9. Great Britain nutrition and health claims (NHC) register. gov.uk.
10. SACN. Advice on fish consumption: benefits and risks, 2004. gov.uk.
11. Gencer B. Marine omega-3 supplementation and the risk of atrial fibrillation: meta-analysis. 2021. PubMed 34612056.
12. EFSA. EFSA assesses safety of long-chain omega-3 fatty acids, 2012. efsa.europa.eu.
13. Dyerberg J. Bioavailability of marine n-3 fatty acid formulations. 2010. PubMed 20638827.
14. Albert BB. Fish oil supplements in New Zealand are highly oxidised. 2015. PubMed 25604397.
15. Jackowski SA. Oxidation levels of North American over-the-counter omega-3 supplements. 2015. PubMed 26688721.

This article is general information, not medical advice. If you are pregnant, have a fish or shellfish allergy, take an anticoagulant or have a heart rhythm condition, speak to your GP or pharmacist first.