Cod liver oil is perhaps the world’s most misunderstood superfood. This article debunks common modern myths and identifies the truths that have maintained the importance of this ancestral supplement for over 2500 years.
First recorded by Hippocrates for medicinal use in Ancient Greece around 400 BC, cod liver oil has enjoyed a storied history ever since.
Ancestral cultures as diverse as the Eskimos and the South Seas Islanders both revered the use of fish liver oils for their health-giving properties, especially with regard to fertility and producing healthy children.
British physician Dr. John Hughes Bennett noted in 1848 that cod liver oil had been utilized since the beginning of recorded history by the fishing communities of Scotland, Sweden, and Norway for its strengthening properties as well as for medicine.
Doctors prescribed cod liver oil to treat rickets, a vitamin D deficiency disease, starting about 1800, perhaps even earlier.
A couple of decades later, in 1820, the practice of using cod liver oil to prevent and treat rickets was widespread in the countries of Germany, Holland and the Netherlands.
The anti-infective nature of cod liver oil due to the natural vitamin A content made it an indispensable remedy for all manner of illnesses prior to the advent of antibiotics including tuberculosis, measles, and diseases of the eyes.
According to the rare and fascinating book Ultraviolet Light and Vitamin D in Nutrition, the United States imported about 1.8 million gallons of cod oil and cod liver oil in 1922.
Five years later, in 1927, the amount nearly tripled to 5 million gallons due to research showing its benefits in preventing rickets.
In 2000, a mere 70 years later, America imported less than half a million gallons of cod liver oil, steep and shocking decline!
No doubt, the drastic move away from cod liver oil in the American diet was due to the foolish reliance of modern medicine on synthetic vitamins, antibiotics, and other pharmaceutical drugs to prevent and treat disease symptoms rather than nutrition and healthy lifestyle to prevent them.
Cod Liver Oil Resurges in Popularity
Since the turn of the millennium, cod liver oil has enjoyed a significant resurgence in popularity as interest in natural remedies and whole food supplements for maintaining wellness grows by leaps and bounds.
The worrisome problem of antibiotic resistance and the growing body of evidence that antibiotics can do significant harm and perhaps even irreparable damage to the gut has motivated forward-thinking individuals to look to the past for effective and safe alternatives.
Unfortunately, this interest has not been without controversy, as confusion and myths regarding this ancient superfood continue to make the rounds on social media, often in viral fashion.
The predominant myths about cod liver oil are discussed in the commentary below.
Myth #1: All Cod Liver Oil is Basically the Same
The truth is that almost all cod liver oil on the market today is heavily industrialized.
This destructive manufacturing process, which includes chemical refining, bleaching, high heat, and deodorization (oil kept at 482 °F/ 250 °C for up to 6 hours) destroys the natural vitamins A and D and damages fragile omega-3 fatty acids.
Synthetic vitamins are typically added back in to meet desired labeling requirements.
So many consumers are fooled by this!
Cod liver oil as used traditionally was not widely manufactured using this violent, denaturing process. Certainly, no synthetic vitamins were ever used.
As a result, if one desires the ancient benefits of cod liver oil, it is important to seek a manufacturer who produces this supplement using no heat or chemicals of any kind to preserve the natural vitamins A and D and prevent rancidity of the omega-3 fatty acids. (sources)
Myth #2: Dangerous Amounts of Vitamin A
It is very important that intake of natural vitamin A is balanced with its synergistic companion vitamin D (and ideally, Vitamin K2 as well).
Unfortunately, some cod liver oils on the market contain very little vitamin D. Worse, it is often synthetic.
Prolonged intake of cod liver oil that contains vitamin A with little vitamin D could lead to symptoms of osteoporosis and other health challenges, according to research performed in Europe.
If cod liver oil has been manufactured in a traditional manner with the natural vitamins A and D preserved in their correct ratios, these problems are avoided, and the benefits of this ancient supplement optimally enjoyed.
Myth #3: Toxins Such as Mercury, PCBs and Dioxins
Modern cod liver oil processing techniques effectively remove heavy metals and other toxins such as PCBs and dioxin.
Combined with traditional rendering methods and batch testing for purity, there is little need to be concerned about toxicity.
The one exception to this is radiation from the 2011 Fukushima nuclear disaster. As radioactive water is still pouring into the Pacific to this day, in my opinion, it is best to source cod liver oil that comes from Atlantic waters. (sources)
Myth #4: Plain Fish Oil is Better
The truth is that most fish oil on the market comes from farmed fish that are treated with antibiotics.
It is a little-known fact that farmed and “sustainable salmon” are fed more antibiotics per pound than any other livestock in North America!
In addition, noncarnivorous species of fish, such as salmon, will eat almost anything. For this reason, they are a popular source for commercial fish oil brands, and are commonly fed an unnatural diet that includes GMO soy and corn.
Another big issue with omega-3 fish oil supplements is that the vast majority of fish oils on the market contain little to no vitamins A and D!
Combined with the caustic chemical and high temperature processing damages the delicate omega-3 fats (EPA and DHA), fish oil is nothing short of a toxic supplement.
In fact, a 2026 study published in the Journal of Prevention of Alzheimer’s Disease found that older adults who take plain fish oil suffer faster cognitive decline than those that don’t take it! Note that the trial was not randomized, so the association is correlative, not causative.
My advice would be to stay far away from omega-3 fish oil supplements!
Myth #5: Good Source of Vitamin D
Most cod liver oil on the market is processed with molecular distillation, which removes most of the natural vitamin D.
Some manufacturers add it back in, but it is usually synthetic and in smaller amounts than would naturally occur in the oil.
Therefore, if one of the primary reasons for taking cod liver oil is the natural vitamin D, it is imperative to seek out a brand that is processed without heat. There are only a handful on the market that qualify, so buyer beware!
While everyone is different…for what it’s worth…this brand of virgin cod liver oil has demonstrated the ability to maintain my personal Vitamin D levels the best over the years.
Myth #6: Cod Liver Oil is Rancid
While MOST cod liver oil is indeed rancid due to high heat processing, there are a few brands of cod liver oil that are not.
Thus, it is important not to throw the baby out with the bathwater when it comes to cod liver oil!
Cod liver oil is an ancient superfood, and as long as it is processed in a manner consistent with traditional methods, it is wise to make use of its therapeutic and nutritive benefits!
According to my research, only two brands qualify as completely raw, unprocessed, and pure as of this writing.
Since 2015, our family has used this raw, Icelandic extra virgin cod liver oil. It is available in both plain and flavored liquid or capsules.
If Dropi is unavailable (it often runs low off-season), another brand to try is this raw, Norwegian virgin cod liver oil.
(1) Ultraviolet Light and Vitamin D in Nutrition
(2) Cod Liver Oil Debate
(3) Cod Liver Oil the Number One Superfood
(4) Cod Liver Oil: Setting the Record Straight
(5) The Yin and Yang of Cod Liver Oil
(6) Is Farmed Fish Really the Answer?
(7) The association between omega-3 supplementation and cognitive decline in older adults
More Information
How to Swallow Cod Liver Oil (without gagging)
Love Blue Ice.
I find it ironic and humorous that you have an ad for Country Crock on your post. Is there a way to choose the ads you show given that that is basically opposite of all things healthy?
I can’t read your articles on my phone, I keep getting spam ads then get redirected. Is it just me?
Hi Leah, your phone has been infected. Visit this website to get the infected app removed. It is not coming from the websites you are trying to visit.
Fermented cod liver oil is the only “supplement” I take
It is cheaper on Amazon.
My gramma talked about it ALL THE TIME!!
I just bought a bottle from your suggested supplements page then the fukashema thing got me concerned. What do you think?
In Russia we have very popular product – canned cod liver. The ingredients are only fresh cod liver and salt. I’m wondering how much of the natural vitamins remains in it?
Canning is a very denaturing process for food and involves high amounts of heat so not confident of the nutritive value there.
I think the article should have explained the need to take it with butter oil to get the fullest benefit. Funny how I read it in your book yesterday!. Also, my opinion is your shopping link should go to the page showing all the options. I have 3 jars of the cinnamon tingle blend on their way! Almost finished the first one and cannot believe how much healthier I am. Well worth the cost. Thanks for all you do!
Shouldn’t that last myth be “ALL cod liver oil is a good source of vitamin D”?