Krill Oil Misinformation

krill oil label
Krill oil supplements are supposed to be protected from rancidity by the natural antioxidant astaxanthin…but astaxanthin is very sensitive and quickly degrades to almost nothing. This leaves krill oil exposed to oxidation and rancidity.

Nutritional misinformation (intentional or not) is very common on the internet. Here are two examples, with a focus on krill oil.

I got several emails about the Dean Ornish piece in the NY Times where he once again blames all our ill health on fat and meat.

(No, Ornish did not talk about krill oil, but misinformation is misinformation, whether it’s about meat or krill oil.)

As always, I am amused and annoyed by poorly supported science pieces. (Perhaps some of you reading this find that ironic…?) Most people will take Ornish at this word. Even scientists with PubMed access may not look up the references to fact-check thoroughly. If you did that, you’d be amused and annoyed too.

This is too big a subject to tackle here and now, but I’ll say this: Ornish’s intervention works because it is multi-pronged: besides avoiding meat, they tell people to strictly avoid sugar, flour, processed foods, Omega-6-rich vegetable oils, and eat a lot of vegetables and some fish oil, manage stress, exercise, and get supportive counseling. And he blames just meat and fat for all you ailments?!

I think patients who follow Ornish’s protocol notice improvements DESPITE meat avoidance, not BECAUSE of it.

I would alter his protocol by replacing some of the cruciferous veggies with probiotic-friendly root veggies and tubers, adding pastured eggs, lots of seafood, occasional liver, grass-fed butter and yes, some red meat. If you took the ancestral people I talk about in this recent previous blog and hypothetically put them on the Ornish diet, I’m guessing they’d develop several modern diseases.

But your average Homer Simpson will thrive on an Ornish diet…initially at least. Bill Clinton, anyone?

An annoyed Dr. Michael Eades points out some of the major flaws with the Ornish approach here.

A krill oil video

In the same vein as the Ornish piece, I saw a video about why krill oil is better than fish oil. Also by someone apparently widely followed.

See the video for yourself here:  It’s called Battle of the Omega-3 Fatty Acids: Krill Oil vs Fish Oil.

Like the Ornish piece, the disturbing thing here is how smoothly facts and almost-facts are weaved together. I’ll try to sort them for you.

Here are questionable facts from the video above:

  • There is a rumor going around that fish oil actually thins your blood and so does krill oil. And it does.
  • When I take too much krill or too much fish oil, I actually get nose bleeds because they thin your blood so effectively.
  •  Fish oil tends to be less stable than krill oil because krill oil contains astaxanthin.

These krill oil claims are not new. They originated from marketing departments of the first krill oil manufacturers. Even Dr. Mercola holds some of these (perhaps convenient) beliefs too. Unlike Ornish, the nutritional arrows of Mercola and Asprey mostly point in the right direction. That’s the surprising bit.

Let’s look at the disputed (boldface or is it bald-face?) sentences in more detail.

“There is a rumor going around that fish oil actually thins your blood and so does krill oil. And it does. When I take too much krill or too much fish oil, I actually get nose bleeds because they thin your blood so effectively.”

Well, this is kind of a half-truth. So I half object.

Yes, in extremely high doses, fish oil can cause some blood thinning. In this instance, we don’t know how much ‘too much’ refers to. If you are a ‘bio-hacker,’ your variables are multiple. Blaming it all on Omega-3 may be just convenient and semi-supported.

If you look at the science (and this has been pretty well studied) the reality is somewhat different. Fish oil does not appear to cause increased bleeding even when combined with anticoagulant drugs like warfarin or coumadin.

Of course, as our mothers told us, we’re all unique little snowflakes. For every person who does not notice increased bleeding, there may be one who does. More on this subject in an older blog.

“Fish oil tends to be less stable than krill oil because krill oil contains astaxanthin.”

This is the over-simplified claim that requires debunking. Science is rarely simple enough to fit on a bumper sticker.

There is no direct evidence to support this statement. All Omega-3 fatty acids and Omega-3 containing oils will oxidize. The molecule form (ethyl ester, free fatty acid, triglyceride, or phospholipid etc.) of the Omega-3 fat influences oxidation. Phospholipids are more prone to oxidation than triglycerides. And krill Omega-3 is in phospholipid form. This suggests the exact opposite, that krill oil will oxidize faster.

In the video’s defense, people think krill oil is more stable because of:

  1. Astaxanthin. Krill contains some astaxanthin. But astaxanthin is notoriously delicate and it degrades very quickly. Milligram quantities quickly become micrograms. In the early days of krill oil, companies used to list astaxanthin levels on their labels. Now, few of them do. Why? Astaxanthin degrades quickly. Barely measurable. This means there is some antioxidant protection provided by astaxanthin when the product is very fresh, but hardly any after a while on the shelves.
  2. Minimal burping involved with krill oil. This is because there is an emulsifying effect provided by the phospholipids in krill oil, so krill oil blends with whatever you’ve eaten and does not float on top of your meal like fish oil might. This makes you not notice the rancidity if/when you burp. More importantly, there is far less Omega-3 in krill oil. Less Omega-3 = less rancidity to be noticed. This does not mean the oil is not rancid. It means you notice less of the rancidity.

So is fish oil less stable?

That depends on many internal and external factors:

  • degree of unsaturation of fatty acids (no difference between fish and krill)
  • how much oxygen the oil has been exposed to
  • light exposure
  • heat exposure
  • UV exposure
  • exposure to metals
  • excessive handling of the oils
  • the antioxidant blend used to protect the Omega-3.

All this has very little to do with whether it is from fish or krill.

Buckle up. It’s going to get a little geeky for a couple of paragraphs.

EPA and DHA, regardless of origin, will oxidize because of the bisallylic carbons between the double bonds. These carbons have low activation energy for hydrogen loss and have a tendency towards free radical formation.

Fish or krill does not matter.

EPA has four bisallylic carbons and DHA five. This is because DHA is a longer molecule and has the potential to oxidize faster/more. Less useful plant Omegas have only 2. Saturated (animal, coconut) and monounsaturated (olive, lard) fats have none, making them much safer from an oxidative stress perspective.

Different oxidation byproducts develop depending on the position of the carbon undergoing oxidation.

As a consumer, you may go to IFOS Consumer Reports and check your product’s rancidity/freshness level.

Acid Value, Peroxide Value, Anisidine Value and TOTOX

You will find Acid value, Peroxide value, Anisidine value and TOTOX listed there.

IFOS Report
Example of IFOS freshness or stability analysis.

Some of these markers are more useful than others.

Acid value is a measure of the amount of fatty acids present in free fatty acid form. In fish and krill oils, Omega-3 is bound to ethyl ester, triglyceride or phospholipid form. When a fatty acid is cleaved, you have free fatty acids. A high measure does not mean the product is rancid – it could mean that some of the Omega-3 is in the free fatty acid form.

The new triglyceride-lowering fish oil drug, Epanova, is mostly free fatty acids. Looking at its acid value will give you a falsely disturbing number. Our EPA 500 tends to have higher free fatty acid levels. All krill oils have high free fatty acid levels.

The first products of lipid oxidation are measured by Peroxide value (PV). It is considered a leading indicator. The PV of an abused or air-exposed oil will rise over a few months. Then, a cascade of reactions that first produced peroxides isomerizes to conjugated dienes and trienes. These are measured as Anisidine value (AV). For example, EPA produces F3-isoprostanes and DHA produces F4-neuroprostanes.

After a few more months, PV drops off and Anisidine value (AV) begins to climb.

PV tends to increase and then fall while AV will tend to rise steadily over time. So if you look at a super rancid krill oil’s PV without sniffing it or looking at the AV, you might falsely believe that astaxanthin is doing a good job protecting it. Not so.

TOTOX is a calculated value, just like your LDL cholestero.

(2 × PV) + AV = TOTOX.

Generally, any product with a TOTOX higher than 20 should be considered slightly rancid, even though the industry cut off is 26.

Then there’s that sneaky trick, steam deodorization. Here, a somewhat stinky oil is exposed to steam and most of the more polar oxidation compounds are partitioned out with the steam, leaving behind much cleaner oil. It’s a sneaky way to get old oil to resemble new.

Recently a study revealed that several fish oil supplements marketed in New Zealand were severely oxidized. As a consumer, there is no way to tell how rancid your product is without third-party testing services like IFOS.

Of course, nothing beats sniffing and tasting the oil!

My point in going through this detail (besides dredging up the subject of my grad school thesis from 25 years ago and feeling like a geezer) is that it doesn’t matter, not one tiny bit, whether EPA and DHA come from fish or krill. In the absence of astaxanthin, krill oil will oxidize just the same. And astaxanthin is virtually absent in most products.

Krill oil has another issue: it goes from red to brown over time. This is from non-enzymatic browning of the amino acids present and can result in the formation of pyrroles and other volatile (read stinky) compounds.

IKOS…to the rescue?

The good folks at IFOS (International Fish Oil Standards) have also begun a krill oil testing program called IKOS – the only one of its kind. IKOS is certainly a step in the right direction, nudging krill oil companies to step into the light. But their test results show that peroxide values are certainly not low – they are all over the map.

The IKOS program is not without its flaws:

  • Anisidine and TOTOX values are disappointingly absent
  • Even though IKOS tests for astaxanthin level, a true astaxanthin level should be measured at the end of the product’s life, not when it’s freshly bottled
  • Non-enzymatic browning is not measured
  • Traces of solvents used to extract and concentrate krill oil is not measured or declared. Typically used solvents are acetone and isopropanol.

It’s been two years since IKOS launched and yet only three (of hundreds?) brands have had the courage to step up.

Krill oil: not more stable than fish oil, just different

Fish and krill oils are both unstable and need to be protected with ultimate care. This means never exposing the oil to air/oxygen and minimizing heat and light.

My beef with krill oil is mostly with the marketing and hype associated with its sale. Krill is primarily a phospholipid supplement…with a tiny little bit of Omega-3 and astaxanthin (if fresh.) Fish oil is just plain Omega-3 and nothing else.

They are not interchangeable in any way. They work differently. They absorb differently and they influence gene expression differently.

Don’t take krill oil because fish oil is ‘less stable.’ Take krill because it is a good source of much needed phospholipids.

Phospholipids are an essential class of fats that helps cell membranes function properly. Want more phospholipids? Eat egg yolks. Or if Ornish has you scared of yolks, supplement with phosphatidylserine or phosphatidylcholine. Or krill.



This website is for your education and general health information only. The ideas, opinions and suggestions contained on this website are not to be used as a substitute for medical advice, diagnosis or treatment from your doctor for any health condition or problem. Users of this website should not rely on information provided on this website for their own health problems. Any questions regarding your own health should be addressed to your own physician. Please do not start or stop any medications without consulting with your doctor. We neither encourage you to do so, nor can we be held responsible for the fall out of failing to seek the counsel of a medical health practitioner.

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Vin Kutty
Vin Kutty, MS, is co-founder of Innovix Pharma. He is a nutritionist, author, and Omega-3 expert with 20 years of experience.


Join the Conversation

  1. Hi Vin – I have been reading about – triglyceride form (TAG) over ethyl ester form. Can you please advice which is better , from absorption perspective. This is being discussed on various forums on the internet including Amazon reviews. There is an article in Amazon which mentions Omegavia 500 switching from ethyl ester to TAG.
    I request you to kindly throw some light on this matter.
    Link :

  2. Hi Vin,
    I’m doing a research on krill oil and fish oil.
    I was interested in your article. It contains very useful information. I would especially like to have more information about oxidation. I want to examine the article you shared so. (Rev. Chem Soc 2010 Nov; 39 (11): 4067-79. Doi: 10.1039 / b922183m. Epub 2010 Jun 9.
    Lipid oxidation and improving the oxidative stability.
    Shahidi F1 Zhong Y.) But I can only get abstract.
    Therefore I ask you to share the entire article from you.
    Thank you for your support,

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