When Never EVER to Use Fish Oil

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Dr. Rudi Moerck is a drug industry insider and an expert on omega-3 fats.

In this interview, Dr. Rudi Moerck explains why fish oil may not be your best source of otherwise healthful omega-3 fats.

Dr. Mercola's Comments:

There's a tremendous amount of confusion about omega-3 oils and it is my intention to help clear up some of the confusion with this article.

First let me preface this with saying that fish oil really started the omega-3 market, and most of the research on the benefits of animal-based omega-3 fats (DHA and EPA), even to this day, are based on studies using fish oil.

Fish oils are typically extracted from menhaden, sardines, and herring; fish that are generally not consumed by the average person. These types of fish are indeed very high in EPA and DHA, and the health benefits of these fats are well established.

Health Benefits of Omega-3 Fat

In fact, most of the health benefits associated with omega-3 fats are linked to animal-based omega-3 fats like EPA and DHA, not plant-based omega-3 fats like ALA.

Even the US FDA, which denies most nutritional claims, acknowledges the cardiovascular benefits of animal based omega-3 fats:

  • Antiarrhythmic: counteracting or preventing cardiac arrhythmia
  • Antithrombotic: tending to prevent thrombosis (a blood clot within a blood vessel)
  • Antiatherosclerotic: preventing fatty deposits and fibrosis of the inner layer of your arteries from forming
  • Anti-inflammatory: counteracting inflammation (heat, pain, swelling, etc.)
  • Improves endothelial function: a major factor in promoting the growth of new blood vessels
  • Lowers blood pressure
  • Lowers triglyceride concentrations

Researchers are also attributing a number of other health benefits to omega-3 fat, including:

Unfortunately, the majority of people who take supplemental omega-3 to protect and improve their health are taking fish oil.

I say unfortunately, because as you will find out, at least 25 percent and maybe even as much as half of the fish oil on the market are damaged products that can do more harm than good…

Why Fish Oil Isn't Your Ideal Source of Omega-3

Yes, despite all the established health benefits of animal-based omega-3 fats, fish oil is actually NOT the ideal source of these fats.

The primary drawback with fish oil is the problem with oxidation, which can occur at any point during the processing, or after you open the bottle. Dr. Moerck explains:

"There are a number of ways in which fish oil can be processed. One is by just simply squeezing the fish -- in some cases with cod liver oil to actually remove the livers from the cod -- and then remove the oil from those by classical mechanical techniques.

In some cases, to get the last few ounces of oil out of the fish, they use solvents, or they use fish oil as a solvent by taking fish oil that's already been processed, using it as an extraction method to get more fish oil out.

Every time fish oil is subjected to contact with oxygen, however, it starts going rancid. It starts oxidizing."

Omega-3 Fats are Incredibly Fragile

Omega-3 fats are extremely fragile and are VERY easily damaged by oxygen. This is true for ALL omega-3 sources, whether animal-based or plant-based.

However, this is where krill oil stands out as a clear winner.

Krill oil would also be highly unstable if it wasn't for the fact that it contains the antioxidant astaxanthin, which keeps it safe from oxidative damage. In fact, in tests performed by Dr. Moerck, the krill oil remained undamaged after being exposed to a steady flow of oxygen for 190 hours!

Compare that to fish oil, which went rancid after just one hour.

That makes krill oil nearly 200 times more resistant to oxidative damage compared to fish oil!

When purchasing krill oil, you'll want to read the label and check the amount of astaxanthin it contains. The more the better, but anything above 0.2 mg per gram of krill oil will protect it from rancidity. Astaxanthin also has other more specific health benefits, such as protecting against:

  • Cataracts
  • Age related macular degeneration
  • Sunburn

Fish Oils Contain Higher Amounts of Contamination

Another primary concern that is not widely recognized is that many of the fish oils on the market are contaminated with relatively large amounts of metals and toxic chemicals. And not just heavy metals. In fact, toxins like mercury are typically screened for, at least in higher quality brands.

But there are other contaminations that are more unlikely to be identified or removed.

Some of the most common contaminants found in fish, aside from mercury, include:

  • PCBs
  • Dioxin
  • PDEs
  • PCP's
  • Radioactive substances like strontium
  • Toxic metals such as cadmium, lead, chromium and arsenic

In fact, a lawsuit filed earlier this year brought the issue of contaminated fish oil to the forefront. Environmentalists in California claim that popular brands of fish oil supplements contain unsafe and illegal levels of carcinogenic chemicals.

They tested a number of products and found that levels of PCBs in fish oil supplements varied wildly, from about 12 nanograms per recommended dose to more than 850 nanograms in the most contaminated product.

Smaller fish, such as herring, sardines, and anchovies fare better than larger fish since they don't have time to bioaccumulate metals and other toxins in their tissues.

"The further down the food chain and the shorter that lifespan of the fish, the less metal it's going to have in it," Dr. Moerck explains.

"So for instance, a salmon is going to have less metal in it than a grandfather tuna. Tuna has a lot of more mercury and other heavy metals in them because they're older fish. They accumulate these things in their body.

Accumulation of these in our own bodies causes all kinds of things like autoimmune diseases."

How to Identify High Quality Fish Oil

According to Dr. Moerck:

"[A]ll the reputable fish oil companies, the big boys in the industry… refine the fish oil and remove as many of the metals as they can.

When you buy fish oils always pay the highest possible price. Usually a price in this case is a good indicator of quality. A very cheap fish oil is not okay," Dr. Moerck warns.

"Don't ever buy it in the clear plastic bottle, or giant bottles like you see at some of these mall-type stores... because the light goes right through them. It's UV damaged. It's rancid. Also, if you have a big bottle of it, you better keep it in a refrigerator because it's going to go rancid.

… I believe very strongly that you do have some excellent fish oil being made. But it's very expensive. If you're going to buy that, you should buy it from a distributor that will ship it to you directly. You don't want to buy it off the grocery shelf because you don't know how long it's been there...

… As far as the fish oils we've seen out there, it's a very wide gamut of quality and stability and rancidity. I would say [25 to] 50 percent of them are rancid."

This is important to realize, because taking a cheap poor quality rancid fish oil will surely do you more harm than good.

"I think that there is some mislabeling going on," Moerck says, "[in] that the expiration date put on there is arbitrary and that the actual shelf life is less. I would bet my reputation on that that is the case – that there is fish oil that is mislabeled as far as expiration date.

We have tested these and we have found a very wide range of rancidity even in the same brand."

However, it may also be an artifact from the processing and manufacturing of the oils, or due to improper storage. The type of bottle used also impacts the oil's tendency to go rancid. Ideally, fish oil should be stored in glass or PET (polyethylene terephthalate) bottles, as they offer the best protection against oxygen.

As a general rule, brands with high turnover also tend to have less rancidity.

To summarize, here are several guidelines you need to follow to ensure you're getting a high-quality, non-rancid fish oil:

  • Avoid fish oil in clear containers, because they will let through ultraviolet and fluorescent light that oxidizes the oil, turning it rancid
  • Buy smaller bottles
  • Have them shipped overnight to your home, directly from the manufacturer
  • Buy from a company with high product turnover to minimize the possibility of getting a product that's been in storage for an extended period of time
  • Store the fish oil in your refrigerator

Some Fish Oil Contain Large Amounts of Added Saturated Fat

Another problem that I was personally unaware of before Dr. Moerck told me, is that some fish oils contain added saturated fats; some in surprisingly high concentrations.

"A few years ago, there was a big controversy in England where people were buying fish oil and then reselling it by adding -- or as they say in the illegal arena, they were "cutting it" -- with a cheaper oil," Moerck explains.

"Fish oil is a relatively inexpensive oil anyway, but then people were adding… lard, to the fish oil. It's important to understand that most fish oil already has some saturated fat, 20 to 35 percent is a saturated fat naturally occurring in the fish. Through processing, you really can't separate it out."

This is one of the reasons why your fish oil turns toward a solid when you put it in the refrigerator.

But how do you know if your fish oil contains extra, added fat?

Dr. Moerck suggests:

"[I]f you look at the label of fish oil, you can usually tell if it's got any added fats by looking at the ratio of total weight and EPA/DHA.

But most people aren't sophisticated enough...They can't really tell. So if you buy, you must buy from somebody that's reputable… [N]ot a mass market-type of product."

What's Your BEST Omega-3 Source?

As far as I'm concerned, unless you can verify the purity and freshness of the fish oil, I recommend you avoid it.

A far better omega-3 alternative -- your safest and most cost effective choice -- is to take high-quality krill oil on a regular basis.

Research has established the similarities and differences between fish- and krill oil, in terms of being beneficial sources of omega-3 fats. This is explained in further detail in an August 24 article in Functional Nutrition.

Nutritionally, both contain DHA and EPA, but their compositions are unique.

According to Functional Nutrition, krill oil typically provides 14 percent EPA and DHA, along with 0.2 percent naturally-occurring astaxanthin.

Fish oil typically provides 30 percent EPA and DHA.

At first glance, it may appear as though fish oil is better simply because it contains a higher ratio of omega-3 fats. However, krill oil is far more efficient, so you actually need far less.

Functional Nutrition explains:

"In fish oil, the omega-3 molecules are attached to triglycerides, which means they must undergo hydrolysis before being absorbed into cells. Krill, in contrast, is attached to phospholipids, [and]… our cell walls contain fats in the phospholipid form…

… The phospholipid structure of the omega-3s in krill oil therefore makes them more rapidly absorbable and allows for easier entry of the omega-3s into our cells and on to the mitochondria and nuclei. The rapid absorption has an added benefit for consumers: There is virtually no aftertaste or fishy reflux that some experience with fish oils."

The conjugation of phospholipids — mainly phosphatidylcholine — with DHA and EPA gives krill oil an edge over fish oil in a number of ways… The phospholipids, by virtue of their connection with omega-3s, are exactly right for proper brain function. Furthermore, they are a part of the eicosanoids system — an extremely important hormone-messenger system in the cells of the body."

I used to recommend taking fish oil or cod liver oil (and I still do in some cases), but aside from the problems discussed above, you also have the issue of overfishing to the point of near extinction, and the potential of toxic contaminations in the oil.

And, as you increase your intake of omega-3 fats by consuming fish oil, you actually increase your need for even more antioxidant protection. This happens because fish oil, as I explained above, is highly perishable.

You have to have sufficient antioxidants to ensure that the fish oil doesn't oxidize and become rancid inside your body, as oxidation leads to the formation of unhealthy free radicals.

This is one of the main reasons I now recommend getting your omega-3 fats from Antarctic krill oil.

With krill oil, you can ensure that you're getting these incredibly healthy fats (EPA and DHA) without having to worry about oxidation issues. Additionally, your risk of getting any mercury contamination is extremely low since krill are so small they don't have the chance to accumulate toxins before being harvested.

I personally take krill oil every day. I particularly appreciate the fact that the omega-3 is attached to phospholipids that dramatically increase its absorption, especially into brain tissue.

Are Krill Sustainable?

Many have been deceived by the fish oil industry atttempt to villify krill by having people believe that using krill is taking food from whales. Nothing could be further from the truth.

For more information on this please review the article I previously wrote last year that addresses this


Potency versus Bioavailability

I had known of krill for about three years before I started to recommend it. The reason I dismissed it initially was I made a simplistic evaluation, like many others do, and merely compared the DHA and EPA concentrations in fish and krill and fish oil was by far a more cost effective choice.

However I am now beyond convinced that this was a mistake.

This is because it is not a straightforward comparison. The amount of DHA and EPA that you need to be concerned with is the amount that actually winds up in your cell and your cell membranes.

This is where krill is the clear winner

Unpublished new data suggest krill oil is absorbed 10 to 15 times better than fish oil. This is because the triglyceride molecule that fish oil is in must be broken down in your gut to its base fatty acids of DHA and EPA. About 80-85 percent is never absorbed and is eliminated in your intestine, which causes about 50 percent of people to have burp back and not tolerate fish oil.

Then once the fatty acids are absorbed into your blood stream, your liver has to attach it to phoshphatidyl choline for it to be used by your body. The amazing beauty of krill is that all of it is in the correct form in the original pill so your body uses virtually 100 percent of it. Additionally it has the powerful antioxidant astaxanthin which prevents the perishable DHA and EPA from going rancid.

And as Dr. Moerck stated above, a large percentage of the fish oil being sold is actually rancid before you even open the bottle as it doesn't contain this protective antioxidant.

Many doctors in Europe are switching from conventional drugs to krill oil to support healthy, normal lipid levels and cardiovascular health. And the great news is that it seems to work at a lower dose, so you may only need one 500 mg capsule per day.

Remember, You Can't Substitute with Plant-Based Omega-3…

Plant-based omega-3 sources like flax, hemp, chia and perilla seeds are high in ALA – the third type of omega-3 fat. ALA is an absolutely essential fatty acid. It is converted in small quantities to EPA and DHA in your body.

Dr. Moerck recommends men to consume a minimum of 1.6 grams a day; women 1.2 grams daily. However, you do not want to consume more than 5 grams a day.

This means that if you eat just 2 tablespoons of chia seeds, you've actually exceeded your daily dose.

Still, I do not recommend using these plant-based sources as a substitute for animal-based omega-3 (DHA/EPA), or as your only source of omega-3.


Because the conversion of ALA to the far more essential EPA and DHA is typically severely impaired by inhibition of delta 6 desaturase. This is an enzyme that is necessary to produce the longer chain EPA and DHA from ALA.

Elevated insulin levels impair this enzyme, and over 80 percent of Americans have elevated insulin levels. So from that perspective alone, plant-based omega-3 simply will not work well for most people.

There are also studies that indicate ALA from flaxseed might actually increase your risk of cancer… In addition, flax seed oil is also used in industrial manufacturing, such as paint, so it can be trickier to ensure that the flax seed you get is actually fit for human consumption, since paint manufacturing does not have to worry about damaging the omega-3...

For these reasons, Dr. Moerck and I agree that flax seed oil is best avoided.

If you want to use flax seed, buy organic, whole seeds, then grind them just before consuming them to ensure freshness. This is also important because, just like fish oil, plant-based omega-3 fats are also highly perishable. For this reason you want to avoid buying pre-ground seeds, because you can be guaranteed that they have been damaged by the time you even get them home from the store.

Personally, I regularly include ALA omega-3 plant based foods, like flax and hemp in my diet, but I always use them in combination with animal based omega-3 fats.

For more information about omega-3 fats, both plant- and animal based, please listen to the interview in its entirety, or read through the transcript.