Cod liver oil, sometimes also referred to as CLO, is a supplement with a long history that is still extremely popular and useful as a source of omega 3 fatty acids for improving your health and increasing your resistance to chronic diseases of all kinds.
It’s often argued as more effective than regular fish oil, and it has the benefits of the omega 3 fatty acids EPA and DHA, which are responsible for the health benefits of all types of fish oil.
We’ve examined the best cod liver oil products on the market and ranked them according to their quality.
1. Carlson Cod Liver Oil
Carlson Cod Liver Oil is an extremely well-regarded supplier of this supplement, and its bottle-based cod liver product is everything you're looking for.
The 500 mL bottle delivers one hundred 5 mL servings, and the only other ingredient is natural lemon flavor–this helps keep the fishy taste of the oil at bay. The total fish oil content per serving is 4.6 grams, and of these, 1.1 grams are omega-3 fatty acids.
With a 500 mg of DHA and 400 mg of EPA, it’s not short on substance. For high-dose fish oil, this is a great way to go.
2. Nordic Naturals Cod Liver Oil
As one of the most widely-known omega 3 fatty acid companies, Nordic Naturals has a reputation for quality, and lives up to it here.
Its liquid cod liver oil supplement uses only natural flavorings and preservatives, like vitamin E and rosemary extract, to increase the shelf life of the oil.
There are 1060 mg of omega three fatty acids per 5 mL serving, which is quite good; the only thing that prevents it from being the top pick is its slightly lower amount of EPA.
3. Athelas Nutraceuticals Cod Liver Oil
Among the softgel-based cod liver oil supplements, the product made by Athelas Nutraceuticals is among the best. With 110 mg of EPA and 100 mg of DHA, the vast majority of the 240 mg of omega 3 fatty acids are comprised of the components you need to get optimal results.
It has no extraneous ingredients, which minimalists will love, though there might be a mild fishy taste to the capsule.
4. Barlean’s Cod Liver Oil
Barlean’s is a bottle-based cod liver oil that is based around freshness–the company even advertises the short shelf life (six months) compared to other companies, who allow their products on the shelf longer.
The omega 3 content is great, with 360 mg of EPA and 540 mg of DHA, though the bottle is only eight ounces, compared to the 16 fluid ounces of some other competitors. Despite this, you can’t go wrong with Barlean’s.
5. Dropi Pure Icelandic Cod Liver Oil
Marketed as a premium cod liver oil supplement, Dropi focuses on purity and high nutritional content. The overall omega 3 content is excellent, at 1150 mg per 5 mL serving, though the EPA and DHA values are middle-of-the-road for a bottle-based cod liver oil supplement.
The other notable facet of this supplement is its unusually high vitamin A content, at 73% of your recommended daily intake. This could be a benefit for some people and a problem for others, since vitamin A is a nutrient that can be harmful when consumed to excess.
So, if you already get a lot of vitamin A in your diet, you’ll want to look elsewhere.
6. Carlson Cod Liver Oil Softgels
While the softgel version of Carlson Cod Liver Oil uses the exact same high-quality oil, the gelatin-based softgel version of the supplement has a disappointingly low dosage.
While it’s certainly possible to just take more softgels, you’ll quickly reach a point where it just makes more sense to get the liquid version, even though measuring precise dosage with liquid supplements can be tricky.
7. Amazing Omega Norwegian Cod Liver Oil
Amazing Omega makes a softgel-based cod liver oil supplement that has a high content of fish oil per capsule, but a disappointingly low EPA and DHA concentration.
In each softgel, there is only 80 mg of EPA and 100 mg of DHA. Amazing Omega does supply fairly high amounts of vitamin A and vitamin D, but those are fringe benefits of taking cod liver oil. The main issue is the content of the omega 3 fatty acids, and specifically the EPA and DHA content.
8. AMRAP Nutrition Cod Liver Oil
AMRAP markets this cod liver oil supplement towards athletes, focusing on its anti-inflammatory properties.
While at first glance the contents look pretty good, a serving size of this is actually two softgels, not one, so you’re getting a half-dose (only 500 mg of cod liver oil) per capsule. It does have a pretty minimalist ingredient design, but the low dosage is a big downside
9. Blue Ice Fermented Cod Liver Oil
The main selling point of Blue Ice is that there version of cod liver oil is fermented. The company claims that the fermentation process “releases the oil” in the cod liver, but seeing as other companies fare just fine in their cod liver oil supplements without supplementation, it may not be necessary.
A report by an independent nutritionist in 2015 incited an uproar when it alleged that the product actually contained pollock oil instead of cod oil, and that it was rancid and contaminated with trans fats. While the company hired several independent labs to analyze their product and now has freshness dates printed on the label, it may be better to steer clear of this one.
10. Solgar Norwegian Cod Liver Oil
Solgar’s cod liver oil supplement is something of a let-down, because the company usually has uniformly high quality across all of its supplements. This one is a bit of an exception.
Each softgel has only 460 mg of cod liver oil, and as you might guess, the omega 3 fatty acid content is a lot lower than that. The EPA and DHA content is only 28 mg each, which makes it very hard to recommend this cod liver oil supplement.
Cod liver oil benefits and side effects
While recently, omega 3 fatty acids from fish oil in general have become very popular in their own right, cod liver oil was the “original” fish oil or krill oil supplement.
Touted as beneficial to your health for decades, it’s now being used to reduce risk factors for chronic disease and fight inflammation.
Since the cod is, after all, a fish, you can expect many of the same benefits as fish oil. What distinguishes cod liver oil is its tendency to have much higher contents of vitamin A and vitamin D.
If you prefer to get your vitamins and minerals from natural sources, the vitamin D will be of particular interest: aside from certain kinds of mushrooms, there are very few other dietary sources of vitamin D (1).
It’s hard to overstate the range of benefits you can see from a cod liver oil supplement. As an excellent source of omega 3 fatty acids, it’s a veritable fountain of health benefits.
Early research in animals found that cod liver oil could help control and even prevent heart disease. A study published in 1986 in the New England Journal of Medicine used a small group of pigs with high levels of blood lipids, which are known to contribute to artery hardening and heart disease.
About half the pigs were fed a cod liver oil supplement for eight months (2). The other half of the pigs were not fed any special supplement, and the hogs were given a diet that was intended to induced heart disease.
The researchers found that the cod liver oil supplement substantially reduced markers of heart disease in the pigs when compared to the control group, and they hypothesized that this happened because the cod liver oil modified the way the pigs’ bodies metabolized certain fat-related hormones.
Naturally, additional research in humans was warranted. Research published in Circulation, a journal published by the American Heart Association, studied the effect of a cod liver oil supplement in blood markers of heart disease in a small group of volunteers (3).
All volunteers consumed a “western diet,” which is known to promote heart disease. As in the study on pigs, the researchers found that blood lipid levels dropped and other biomarkers of cardiovascular well-being improved too.
Eventually, larger studies were carried out, and researchers identified the omega 3 fatty acid content as the reason for the impressive cardiovascular benefits of cod liver oil.
A scientific review article by Phillip C. Calder in the journal Clinical Science evaluated the range of mechanisms by which the omega 3 fatty acids in cod liver oil help reduce your risk for heart disease (4).
The omega 3 fatty acid content, according to Calder, lowers levels of blood triglycerides, helps decrease the production of inflammatory compounds in the blood, and even increases heart rate variability. All of these are positive steps when it comes to heart disease, since high triglycerides, lots of inflammation, and low heart rate variability are all associated with heart disease.
Calder also cites several epidemiological studies demonstrating the benefits of omega 3 fatty acid consumption, particularly in people who are at high risk for cardiovascular disease.
One unexpected benefit of cod liver oil appears to be a potential for it to reduce your risk for type I diabetes, either when consumed by a pregnant woman before giving birth, or during childhood.
Research published from the National Institute of Health in Norway compared mothers of children with type 1 diabetes to a matched control group of mothers of children similar in many regards, except that they did not have type 1 diabetes (5).
The results showed that mothers of children without type 1 diabetes were more likely to take cod liver oil, perhaps indicating that there may be a protective effect associated with cod liver oil.
The same authors replicated this finding in a case control study of children with type 1 diabetes (6). Using a mail survey, the researchers again matched children with type 1 diabetes with children from similar backgrounds who did not have type 1 diabetes. The researchers found a protective effect; using cod liver oil conferred about a 25% reduction in risk of type 1 diabetes during the first year of a child’s life.
Mothers and children should be especially conscious of the vitamin A content of any cod liver oil supplement they use, though; research in rats has found that excessive levels of vitamin A intake can cause birth defects (7).
If you don’t want to tally up your vitamin A intake so you can be sure taking a cod liver oil supplement is okay, you can also take a regular fish oil supplement, which shouldn’t have as much vitamin A in it.
The omega 3 fatty acids in cod liver oil is exceedingly safe. Aside from a few scattered reports of very mild and transient gastrointestinal discomfort, no side effects are known to be associated with omega 3 fatty acids.
The one thing you do need to be wary of is the vitamin A content of your cod liver oil supplement. Since vitamin A is fat soluble (hence why you’d find it in an oil supplement), your body can’t get rid of excess vitamin A very easily, so high doses of vitamin A can be harmful to your health, according to the United States National Institutes of Health (8).
The American Heart Association currently recommends 1000 mg of fish oil per day for people with cardiovascular disease.
Even for those who are healthy, that’s not a bad place to start (9). However, if you already know you have high blood lipids and want to be proactive about lowering your risk for heart disease, you can consider 2000-4000 mg of fish oil per day.
In the case of cod liver oil, keep in mind the caveats about vitamin A content–you don’t want to increase your intake of cod liver oil so high that you exceed your recommended daily intake of vitamin A. Don’t forget, you’ll have to take into account all of the other sources of vitamin A in your diet, too.
Despite its decidedly old-school origins, cod liver oil is still an excellent supplement for anyone who wants to improve their cardiovascular health and fight inflammation.
The optimal dosage for most people is 1000 mg per day, but you should be conscious of the vitamin A content of your cod liver oil supplement. The best cod liver oil supplements deliver high doses of omega 3 fatty acids with only a moderate amount of vitamin A.