How to Choose and Understand Cod Liver Oil

The confusion over the Green Pastures’ fermented cod liver oil continues.

Many people feel very uncertain what to believe right now — or who.  They aren’t sure which test results to trust, or why.  Right now, there’s a lot of he-said-she-said going on, and a lot of wild speculation about who is being paid what to say which.

In my opinion, all parties involved mean well.  Nobody is being paid to promote a specific agenda; everyone truly believes in what they are sharing.  It’s not really worth our time, anyway, to smear any individuals involved in this situation.

We still need to know the truth, though.  What is historical cod liver oil production?  What did Dr. Price recommend?  And what has modern science taught us about the different production methods — and which is the best now?

History

First we’re going to look at the history.  The majority of sources out there quote Dave Wetzel, the owner of Green Pastures (even Wikipedia does).  We need something unbiased.  Something original, that doesn’t have anything to do with this current situation.

I was able to find and read a text called Cod Liver Oil and Chemistry, published in 1895.  It is a public domain work now, so it was available for free, in full.  You can click the link to read it yourself, but it’s long.  Skip the first several sections, as they describe what Norway is like, and what fishing is like, before they get down to the nitty-gritty on cod liver oil production.

Interestingly, I read somewhere that this was the book where Dave Wetzel got his process and information.  If so, why not be transparent and cite it?

In the text, we learn that cod liver oil production dates back to roughly 1000.  From the time CLO production began until 1853, it was indeed done in the method GP uses today.  The text states that after catching, cod are split down the belly on the way back to shore.  Roe and livers are tossed into separate barrels.  A healthy liver is described as cream colored, fat, and extremely soft.  An unhealthy liver is slimmer, harder, and reddish in color.

From the text (emphasis mine):

…they seldom find time to open their liver barrels before the month of May. By this time the livers are, of course, in an advanced stage of putrefaction. The process of disintegration results in the bursting of the walls of the hepatic cells and the escape of a certain proportion of the oil. This rises to the top, and is drawn off.

But in 1853, a man named Peter Moller invented a new process for making cod liver oil — steam production.  This new method required very fresh livers, less than 12 hours old.  It produced a raw, pale, medicinal oil.

The book says about the newly invented processes for extracting these pale yellow oils (emphasis mine):

The buyers, accustomed to the brown oils prepared from putrefyed livers, actually refused to believe that the odorless and almost colorless and tasteless product of the new method could be cod liver oil at all.  It was only with great difficulty that they were convinced; but when at length it came to be understood that the oil really could be made without the undesirable qualities which for centuries had been supposed to be necessary — because irremovable — evils, then the whole scene changed.  

This new pale-colored oil was considered better, and the only reason that “fermented” cod liver oil was ever produced was because there was no better method.  It was considered undesirable but necessary, was knowingly produced by allowing putrefaction to occur with the livers, and was quickly replaced with better methods and cleaner, healthier raw oil as soon as possible.

Why has GP substituted the word “fermented” for “putrefied” used in the book…and gone on to deny that the cod liver oil is, in fact, putrid?

The text also says:

It was these decomposition products that gave the oil what was supposed to be its characteristic brown colour and far from delightful smell and taste. They were derived from the putrefaction of the albuminous constituents of the liver, and it was very natural that they should be supposed to be part and parcel of the oil when that was obtained by leaving the livers until, by putres- cence, the hepatic cells were broken up, and the oil globules in them allowed to exude.

The book even goes on to say (emphasis mine):

The introduction of the steam process, however, showed that these products of putrefaction were not an essential constituent of cod-liver oil from the chemical point of view ; and from the therapeutical, subsequent experience has shown that they have nothing to do with the beneficial action of the oil, if indeed they do not detract from it.

By 1894, the newer methods had taken over in Norway.  Almost all cod liver oil produced for medicinal use was of the pale variety.  It’s likely that this is the variety that Dr. Price would have run across in his travels, and likely the type he recommended.

It appears that GP read the text, substituted “putrefaction” for “fermentation,” and promoted it as an old-world method that was superior.  I believe they actually believed that; but I think doing so was an error.  The text is clear that the by-products of putrefaction were undesirable.

However, the fact that people used CLO as a remedy for hundreds of years using that method shows that it is not inherently dangerous, and has benefits.  It likely just comes with certain drawbacks vs. the pale-colored, fresh CLO.  This is why so many people have still experienced benefit from GP’s products.

This doesn’t, however, make them “superior” or “the best CLO” as advertised.  Let’s take a quick look at what modern science says about oxidation and the by-products of such a production method.

Oxidation

First we need to understand what oxidation is, and why it matters with fats.  All information about oxidation is taken from here.

Oxidation is the process by which fats break down, due to exposure to oxygen.  It happens to all oils and cannot be stopped, but it can be minimized/slowed when oils are processed very carefully.  It happens most quickly to oils that are mostly polyunsaturated, because their oils are the most fragile.  This is especially an issue for marine oils (like fish and cod liver oils).

Oxidation occurs more rapidly when there is heat, light, moisture, and oxygen exposure.  (It’s why most vegetable oils on the grocery store shelves are already rancid when you buy them.)

Signs of primary (early) oxidation:

• Peroxides
• Dienes
• Free fatty acids

Signs of secondary oxidation:

• Carbonyls
• Aldehydes
• Trienes

There is also tertiary oxidation, or late oxidation.

Let’s look at peroxide values first.  The source I cited above states that peroxide values (PV) should be less than 10, and possibly as low as 2.  According to Green Pastures’ recent rebuttal, their oil has a high of 20, and a low of around 10 in their tests.  This places them on the high side, and shows some rancidity.  The long-term PV test shows them peaking around 10 (after 12 months), and then dropping back down to almost nothing by 2 years (which, from what my source says, shows significant rancidity, as PV values drop as they turn into other components).

Green Pastures’ Anisidine levels measure between 3 and 7 over time, according to their data.  This is rather odd, because the source I cite above states that a value of less than 30 is ideal, and “as low as 10” may be required.  GP’s values are incredibly low.

The test data we have from GP doesn’t make sense — for early oxidation/rancidity.  But, we don’t have enough evidence to definitively know what’s going on right now.  The evidence points to rancidity but it’s not fully conclusive.  We need to test for products of secondary and tertiary oxidation to get a better idea of what’s happening.  Historical data supports the idea that it’s rancid, but modern science hasn’t shown for sure.

Let’s take a look now at nutritional profiles.

Expected Analysis

The two most common species of fish that are used for cod liver oil are the Alaskan pollock, and true cod.  The analysis for expected nutrition is from this book.  A lot of people have said that the pollock are a type of cod, so it doesn’t really matter which was used.  But, in fact, it does.  As seen below, the nutritional profiles of the two fish are not the same.  Pollock is much lower in the key omega-3s.

Alaskan pollock liver oil analysis:

• A member of the Gadidae family (Gadus chalcogrammus)
• 15% saturated fat
• 50% monounsaturated fat
• 15% omega-3 (13% EPA and DHA)

Iceland cod liver oil analysis:

• A member of the Gadidae family (Gadus morhua)
• 18% saturated fat
• 53% monounsaturated fat
• 24% omega-3s (23% EPA and DHA)
• EPA: DHA ration of 3:5

Brands of CLO

What we need to know now is — how do the major brands of CLO stand up to the expected analysis?  Do they contain the right amounts of nutrients, in the right proportions?

I’m going to list all the info for every brand, grouped by “not recommended,” “good,” and “best.”  I’ll also give notes on what I think of the brand based on this analysis.  All of these are analyzed based on a 1-tsp. serving (5 grams).

Best

Vital Nutrients (Gadus morhua)

• Total fat: 4g
• 0.5g saturated fat
• 2g monounsaturated fat
• 1200 mg omega-3s
• 320 – 510 mg EPA
• 460 – 640 mg DHA
• Vitamin A: 1800 IU
• Vitamin D: 180 IU
• PRICING: Unknown, please find a health practitioner who offers this

This brand is only available to health practitioners.  The EPA + DHA ratio is 19.5% – 28.8%.  The EPA: DHA ratio is roughly 7:10 which is close.  This type, if available, appears to be an excellent choice.  The only small red flag is that the A:D ration is exactly 10:1, which is considered “optimal.”  It has likely been standarized to be this way, meaning some processing likely occurred.

Rosita (Gadus morhua)

• Total fat: 4.5g
• Saturated fat: 0.9g
• Total omega-3s: 1460 mg
• 500 mg EPA
• 710 mg DHA
• Vitamin A: 3000 – 5000 IU
• Vitamin D: 400 – 500 IU
• PRICING: $50 for 150 mL (5 oz.)

It was difficult to find information for this brand, and I spent quite a bit of time searching their site.  It’s all buried somewhere, but not easily accessible as it should be. This seems a bit secretive and annoying. The DHA + EPA percentage is 26%. which is high even for true cod.  The EPA: DHA is about 5:7, which isn’t quite right.  It seems to be a very good choice, though.  The ranges of A:D are within what we would expect for this type of fish and the ratios are close but not exact — meaning they likely haven’t been altered.

Dropi (where to buy) (Gadus morhua)

• Total fat: 4.6g
• Saturated fat: 0.8g
• Monounsaturated fat: 2.3g
• Total omega-3s: 1150 mg
• 450 DHA
• 350 EPA
• Vitamin A: 2417 IU
• Vitamin D: 172 IU
• PRICING: $53 for 220 mL (7.3 oz)

Cod liver oil is cold-pressed and not refined or processed.  This brand is coming to the US in September. The EPA + DHA percentage is 17.4%.  The EPA:DHA is 7:9 which is a little off, but not much.  The A:D ratio is a little off, and a little low, but I translated these numbers from ug, so it’s possible they may be a little off — they’re close to what we’d expect, though.

NutraPro International (they confirmed they only use Gadus Morhua)

• Total fat: 5g
• Saturated fat: 1g
• Total omega-3s: 600 mg
• 700 DHA
• 500 EPA
• Vitamin A: 2500 IU
• Vitamin D: 250 IU
• PRICING: $33 for 8 oz.

Edited: The company contacted me and pointed out that the DHA and EPA levels were incorrect.  They are actually what is now listed.  The company had switched the EPA and DHA levels on the labels, and I forgot to double them to account for serving size.  It’s now 24%, which is a little high but pretty close to right.  It’s also got a ratio of 5:7 which is fairly close.  They also confirmed that they only use Gadus Morhua.  The A:D is also 10:1, suggested that it’s been standardized, and both are on the low side.

Good

Carlson’s (fish type not stated)

• Total fat: 5g
• Saturated fat: 1g
• Monounsaturated fat: ?
• Total omega-3s: 1100 mg
• 500 DHA
• 400 EPA
• Vitamin A: 850 IU
• Vitamin D: 450 IU
• PRICING: $30 for 500 mL (16.7 oz)

Oil is extracted through steaming, which is a traditional method but not the optimal choice.  The vitamin A:D ratio is concerning as well, it’s almost 2:1 when it should be closer to 10:1.  The EPA + DHA is 18%, which is lower than we’d expect for true cod, and higher than for pollock.  EPA:DHA is 4:5 which is off.

Sonne’s(fish source not stated)

• Total fat: 4g
• Saturated fat: 1g
• Monounsaturated fat: 2g
• Total omega-3s: 1000 mg
• 440 mg EPA
• 440 mg DHA
• Vitamin A: 4000 IU
• Vitamin D: 400 IU
• PRICING: $17 for 16 oz.

This cod liver oil says that it’s from Norwegian cod, but doesn’t state which variety.  Its EPA:DHA is way off, at 1:1.  The A:D is exactly 10:1, which means it’s likely standardized.  The amounts of omega-3s and vitamins are good, though.  It is also purified by molecular distillation (which means the vitamins are likely added/synthetic).

Not Recommended

Garden of Life (cod source not named)

• Total fat: 4.5g
• Saturated fat: 1g
• Total omega-3s: 1400 mg
• 400 DHA
• 447 EPA
• Vitamin A: 4500 IU
• Vitamin D: 450 IU

The DHA + EPA percentage is 18.8%.  The EPA:DHA is almost 5:4 which is way off.  The A:D ratio is exactly 10:1 which likely means it has been standardized.  This may well have been refined in some manner, and is likely a mix of different fish.

Nordic Naturals (fish type not stated)

• Total fat: 5g
• Saturated fat: 1g
• Monounsaturated fat: ?
• Total omega-3s: 1050 mg
• 485 DHA
• 350 EPA
• Vitamin A: 425 – 2950 IU
• Vitamin D: 0 – 20 IU

Their ingredients include “purified arctic cod liver oil” which means some type of refining has occurred.  Baby versions use soybean oil mixed in.  The percent of EPA + DHA is 16.7%, which is close to what we’d expect for pollock, and much lower than what we’d expect for true cod.  The EPA:DHA is 7:10, which is close.  A and D are incredibly low, especially D!  Basically no benefit in this area.  I would absolutely not recommend this.

Green Pastures (fish source not stated; thought to be Alaskan pollock)

• Total fat: 5g
• Saturated fat: 1g
• Monounsaturated fat: ?
• Total omega-3s: 21.2%
• 5.8% DHA
• 12% EPA
• Vitamin A: 2350 IU
• Vitamin D: 980 IU

Most of the data is not included on the product label (except total and saturated fat) and has been pulled from their test results here.  This has about 17% DHA and EPA, which is more than we’d expect from pollock (around 13%), but less than we’d expect from true cod (around 23%).  This may mean a mix of different fish.  EPA:DHA is almost 2:1 which is extremely far off. A:D ratio is rather high, and D especially is very high for what we’d expect.  There is no evidence that D is increased by their “fermentation” process, although a lot of people have speculated or assumed this.

Final Thoughts

So how did this all happen?

We’ve come to trust “natural” and “traditional/ancient” processes more than we do more modern processes.  And usually, that’s a good thing!

We also have come to believe that color is a sign of nutrition and health benefits.  We’ve believed that the more pale something is, the more it lacks nutrition — or, it may have even been bleached or deodorized to obtain that pale color.  We’ve seen other CLO and fish oil brands advertise their amber color vs. others’ nearly clear color as being better because it’s obvious that it’s unrefined.  So, the “color scheme” played a big role.

And, we’ve come to believe that “fermentation” is always a good thing.  Which it is, when it produces those awesome strains of bacteria that help our guts!  But this is not one of those cases.

All of these combined to make FCLO seem like the perfect product.  It was using an ancient process, it was dark in color, and it was supposedly “fermented.”  All the things we typically look for in a super food!

Only, most of us had no idea what to really look for in a quality CLO.  And in fact, “best practices” for CLO don’t match the above criteria!  Instead, we have to look at the nutritional analysis, and we have to look for rapid cold-pressing and careful handling (which produces that pale oil).  Both the historical text and modern science support this.

I believe everyone got a little carried away by the traditional/color/fermentation issues — including GP itself.  And I believe that for many people, FCLO can and did produce good results.  Cod liver oil is that powerful and that amazing that even produced through allowing livers to putrefy, it still has health benefits.  But, many people are also very sensitive to the by-products of this method, and experienced serious drawbacks.

I can’t say that you “must” stop taking FCLO if you believe it is best for you.  I would advise serious caution, though.  And I would never advise anyone who felt they were reacting badly to keep trying it — look for another brand!  I will definitely be looking for another brand for my family — one of the ones I listed above.  Once I’ve had a chance to try it, I’ll report on how we’re liking it.

How do you feel about cod liver oil now?  Which brand will you choose?