Anyone who takes a daily cod liver oil capsule or fish oil supplement quite clearly cares about their health.
The marine-derived dietary supplements are among the most popular natural products on the market, rich in omega-3 fatty acids which variously contribute towards the brain, heart and eyes.
The question is, which is better: cod liver oil capsules or fish oil softgels?
In this article, we’ll cover the key differences between these popular natural supplements and help you make a more educated purchase.
The Key Differences Between Fish Oil and Cod Liver Oil
There are, as you might expect, many similarities between fish oil and cod liver oil, the main being that both are derived from fish (what else?) and as such are high in anti-inflammatory EPA and DHA fatty acids.
However, the differences are equally notable.
Perhaps the primary one is that cod liver oil, as per its name, is extracted from the livers of cod fish – as opposed to fish oil, which derives from the flesh of various cold-water oily fish such as sardines, herring, anchovy or mackerel.
This is an important distinction. Why? Because the liver is biologically used to process toxins.
Given the increasing environmental pollution of our oceans, and the fact that the liver can accumulate heavy metals over time, many people are understandably concerned about consuming oil specially derived from livers.
But doesn’t the flesh of fish also accumulate toxins? Absolutely – particularly if they are harvested from heavily-polluted oceans.
However, numerous studies of cattle and pigs have shown that heavy metal accumulation is higher in the liver and kidneys – unsurprising given the functions of these organs.
Another study from 2007 looking specifically at the bioaccumulation of heavy metals in freshwater fish organs determined that “the liver accumulates relatively higher amounts of heavy metals.”
Although cod liver oil undoubtedly has many health benefits, nonetheless it is disappointing that this distinction is rarely discussed, even if some brands go to great lengths to procure lab reports attesting to the purity of their cod liver oil capsules.
Indeed, as a consumer this is something you should insist upon before parting with cash: a certificate of purity ensures you’re getting the best quality, and independent assessors such as Labdoor put products through a battery of tests to ensure they meet high standards using various criteria.
Another separate, but linked, point is that cod is not a small-species fish; and thus is likely to bioaccumulate more toxins than lesser-lived, smaller species such as mackerel and herring.
There are many adverse effects from ingesting heavy metals and other industrial contaminants (PCBs, dioxins, PBBs) in the water, but that’s another article for another day.
2. Vitamin content
Unlike fish oil, cod liver oil naturally contains small amounts of vitamin A and D – although many brands actually add synthetic A and D after processing has stripped out the natural stuff.
The vast majority of fish oils, meanwhile, contain purely omega-3.
Some have voiced concern about the vitamin A content of certain cod liver oil supplements, since they have been known to exceed the recommended maximum intake while containing only tiny traces of vitamin D.
This is no good thing, as having the proper ratio of vitamin D to A – the ratio the human genome evolved on – is vital for good health.
Skewing the natural ratio, as many supplements do, actually negatively impacts the effectiveness of vitamin D itself.
Although vitamin A deficiency is a major problem in the developing world, hence the need for NGOs like Vitamin Angels to dispense life-saving vitamins to at-risk populations, it is extremely rare in the Western world and there is no need to ingest active vitamin A in the massive quantities provided by many cod liver oil brands.
According to the NHS, “you may be at risk of having too much vitamin A if you have liver or liver products more than once a week; this is particularly important if you’re pregnant.”
The guidance goes on to advise: “If you take supplements containing vitamin A, make sure your daily intake from food and supplements doesn’t exceed 1.5mg.”
The tolerable upper limit for vitamin A is around 10,000 i.u. per day, but bear in mind that this only includes the retinol form, not beta-carotene such as that which comes from various fruit and vegetables.
If you are keen to use a cod liver oil supplement, it would be wise to ensure the vitamin A content is well below 10,000 i.u. per serving, perhaps between 3,000-5,000 – providing sufficient vitamin D is supplied, so as not to affect the desired balance.
Cod liver oil containing natural vitamin A and D is rare and expensive, but it is the best choice as this form of vitamin A is safer at higher dosages.
It would also be prudent to choose a product which uses cold extraction and is from wild-caught sustainable fish in relatively unpolluted waters.
As a side note, it is generally recommended to take vitamin K2 with your vitamin D, since K2 prevents calcium from depositing in your arteries and D helps the body better absorb the mineral.
3. Omega-3 content
Omega-3 fish oils, it’s fair to say, are much richer in essential fatty acids than their cod liver oil counterparts.
Since most of the benefits of these two products stem from their EPA and DHA content, and a significant dosage is required to exert the expected anti-inflammatory effects, fish oil trumps cod liver oil in this regard.
It should be pointed out that there is no set recommended daily amount of omega-3, although most recommend a minimum of 250-500mg combined DHA and EPA per day: and that’s if the adult is healthy and not, say, rebounding from a cardiovascular event for which an omega supplement offers a measure of protection (in March 2017, the American Heart Association issued guidance recommending omega-3 supplements for secondary prevention of cardiovascular disease).
In this circumstance, 1,000mg of EPA and DHA each day might be necessary. Patients who urgently need to lower triglycerides are actually advised to consume between 2,000 and 4,000 EPA/DHA per day, under a physician’s care.
In most cases it would take an inordinate number of cod liver oil capsules to achieve this recommendation.
Any increase in anti-inflammatory omega-3s should of course be balanced with a decrease in pro-inflammatory omega-6; the ideal ratio is 1:1, but the traditional Western diet is skewed in favour of omega-6, by as much as 10:1 or even 15:1.
Omega-6 is most prevalent in processed oils such as soybean and canola.
The European Food Standards Agency has declared that 5,000mg per day from supplements is safe, although it’s fair to say that such a high dosage is not necessary for most people, who will get just as much benefit from 500-1,000mg per day.
That said, there are many naturopathic doctors and holistic practitioners who suggest a daily dosage of 1,000-2,000mg for the ageing (50+).
Cod Liver Oil vs Fish Oil: Other Considerations
There are other factors you might want to consider when weighing up the relative merits of cod liver oil vs fish oil. One is that many cod liver oil brands…don’t actually use cod! Talk about mis-selling. These unscrupulous brands use fish such as haddock and pollock, as they are cheaper sources of oil.
Highly refined and oxidised supplements are best avoided, which is again where third-party lab results come in.
Solvents used by some manufacturers to extract omega-3s have raised safety questions and will certainly impact the clinical effects.
If your fish oil capsule or softgel smells overpoweringly of fish – don’t trust it. The same applies if a capsule causes ‘fish burps’. These are signs of a poor product.
However, a slight fishy odour can generally be expected and is nothing to worry about.
Hopefully this article will help you decide between cod liver oil capsules and fish oil softgels. At any rate, you will now know the key differences between these popular supplements.
Remember, if you’re contemplating buying an omega-3 supplement, you should always consider purity, omega content (seems obvious, but you’d be surprised!), freshness, potency, bioavailability, sustainability and taste.
Price will naturally be a factor, but it makes no sense to buy a health supplement that, while cheap, provides no meaningful health benefit.
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Patients who urgently need to lower triglycerides are actually advised to consume between 2,000 and 4,000mg EPA/DHA per day, under a physician’s care.