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Fish Oil, Salmon Oil, Cod Liver Oil, Krill Oil: What’s the Difference?

By Bo Martinsen, MD

Fish Oil, Salmon Oil, Cod Liver Oil, Krill Oil:  What’s the Difference?Today, the omega-3 industry is specializing more than ever. On the supermarket shelf, you don’t just find fish oil any longer, but a broad range of products under that main heading.

As we get a greater selection of omega-3 products, how do you decide what to pick? One helpful method is to consider the source of the oil.

Regular Fish Oil
Fish oil is in many ways a wide category term. It’s oil made from fish. If you are talking about fish oil, you could mean an oil coming from a particular variety, including cod or salmon. For the rest of this article, however, I’m going to discuss regular fish oil as a specific category, and one that is manufactured in a different way from cod liver and salmon oils.

The great majority of the world’s fish oil is a byproduct of the animal feed industry (1). This includes the capsule products sold at Walgreens and Costco, as well as the fish oil used as a base for pharmaceutical omega-3 oils. The oil comes from anchovy, herring, sardines and mackerel, typically fished off the coast of South America, North Africa or China. While the fish meat gets ground into pellet feed, the oil is multi-purposed. Some of it goes towards fish feed and pet food. The rest is refined and encapsulated for human consumption. As the Norwegian newspaper Aftenposten explained, there’s often no quality control differentiation between the oil destined for people and animals before the refining process (2).

This origin story explains why regular fish oils typically taste and smell bad and often produce fishy burps. Since the main goal is to produce fishmeal, the manufacturers have little interest in maintaining the quality of the fish oil. The oil is usually extracted last and often goes rancid within a short period of time. New techniques enable manufacturers to make the oil taste less offensive. However, you can never restore a rancid fish oil back to freshness.

As for the nutritional profile, some of these fish oils have the highest omega-3 content – up to 30% combined EPA/DHA (3). On the other hand, half of the fats are saturated, or the double of what is found in salmon or cod liver oil. Depending on the fish oil product, it typically takes 8 to 10 large capsules to get a daily clinical dose of 3000 mg EPA/DHA.

As we get a greater selection of omega-3 products, how do you decide what to pick? One helpful method is to consider the source of the oil.

Regular Fish Oil
Fish oil is in many ways a wide category term. It’s oil made from fish. If you are talking about fish oil, you could mean an oil coming from a particular variety, including cod or salmon. For the rest of this article, however, I’m going to discuss regular fish oil as a specific category, and one that is manufactured in a different way from cod liver and salmon oils.

The great majority of the world’s fish oil is a byproduct of the animal feed industry (1). This includes the capsule products sold at Walgreens and Costco, as well as the fish oil used as a base for pharmaceutical omega-3 oils. The oil comes from anchovy, herring, sardines and mackerel, typically fished off the coast of South America, North Africa or China. While the fish meat gets ground into pellet feed, the oil is multi-purposed. Some of it goes towards fish feed and pet food. The rest is refined and encapsulated for human consumption. As the Norwegian newspaper Aftenposten explained, there’s often no quality control differentiation between the oil destined for people and animals before the refining process (2).

This origin story explains why regular fish oils typically taste and smell bad and often produce fishy burps. Since the main goal is to produce fishmeal, the manufacturers have little interest in maintaining the quality of the fish oil. The oil is usually extracted last and often goes rancid within a short period of time. New techniques enable manufacturers to make the oil taste less offensive. However, you can never restore a rancid fish oil back to freshness.

As for the nutritional profile, some of these fish oils have the highest omega-3 content – up to 30% combined EPA/DHA (3). On the other hand, half of the fats are saturated, or the double of what is found in salmon or cod liver oil. Depending on the fish oil product, it typically takes 8 to 10 large capsules to get a daily clinical dose of 3000 mg EPA/DHA.

On the plus side, sea farmed salmon oil is often fresher than the wild version because the time from harvesting the fish to processing the oil is shorter.

If you happen to find a salmon oil that comes from wild salmon, the fatty acid balance resembles cod liver oil, but contains less omega-3. In addition, wild salmon oil is often rancid because of the long transportation time and because the fish is often stained with blood, which oxidizes the oil.

Cod Liver Oil
Cod liver oil is the original omega-3 source. Already in the 1700s, doctors were recommending cod liver oil for patients with joint pains, although its rich history dates back further (6). Considered a safe food product, cod liver oil is especially recommended for children and pregnant women in countries like Norway (it’s worth noting, other omega-3 sources do not enjoy the same government-endorsed status) (7).

Part of the reason cod liver oil has been used for so many years is that the oil is easy to extract. The cod liver contains its omega-3 rich oil in small vacuoles. When the oil is extracted, there is limited amounts of rancidity-creating blood present. However, since the oil was historically left in open vats and exposed to heat and oxygen, the poor taste became notorious and limited its popularity. With modern technology and increased focus on freshness, cod liver oil has come a long way. For instance, Omega Cure® cod liver oil is tasteless and can even be used in chocolates or cookies.

Looking at the nutritional profile, cod liver oil is the only omega-3 source that also contains significant amounts of vitamin A and D*. As for the omega-3s, it typically contains around 20% EPA/DHA, and has only half the amount of saturated fats of regular fish oils. To get a clinical dose of 3000 mg EPA/DHA, you would need to consume one tablespoon (15 ml) of oil or 15 capsules.

Of course, not all cod liver oils are alike. While Omega Cure is a fresh, full-spectrum cod liver oil, store-bought cod liver oils are typically highly refined and rancid.

Krill Oil
Although not derived from fish, krill oil is also a popular omega-3 source. How does krill oil compare?

Like regular fish oils, krill oil is a byproduct from the animal feed industry where the main goal is to make feed for chicken or sea farmed fish. Compared to the above fish oil products, however, krill oil is much harder to extract. The manufacturers typically use solvents to extract the oil. In some cases, the use of these chemicals can have serious consequences. In 2012, for instance, chemicals caused a deadly explosion at one krill oil facility (8).

Depending on the product, krill oil typically contains somewhere between 15 to 25% EPA/DHA. Krill oil has become popular because the labels claim you only need one small capsule a day. Looking at the research, however, you have to wonder what that one capsule is supposed to be achieving. Even the krill oil manufacturers’ own studies show that you need more than 4 capsules per day to get any meaningful increase of omega-3 in the body (9). And if you look at the amount of EPA/DHA per capsule, it would take more than 20 capsules to reach a clinical dose of 3000 mg EPA/DHA.

So far, krill oil lacks the scientific support that cod liver oil and fish oil have in spades. The manufacturer’s claim that the astaxanthin antioxidant renders additional benefits has not been proven, nor that the special phosholipid form makes any difference in terms of bioavailability relative to other fish oils (10, 11).

The krill oil manufacturers also struggle with rancidity issues. At the cost of 5 times as much per omega-3 unit than regular fish oil, you’ve got to wonder if krill oil is worth it. Particularly until researchers learn more about its efficacy and safety.

What’s the  Main Message?
Taking a clinical EPA/DHA dose of any of these omega-3 oils should lower triglyceride levels in the blood. However, the manufacturing methods, the freshness factor, and the nutritional profiles of the oil will also impact clinical effects.

In many ways, we should stop talking about omega-3 in general and start clearly attributing the source of the omega-3 oil and the dose in reporting the results from new studies. Right now, it’s as if we are making a judgement about the health benefits of grains, without mentioning whether we’re discussing barley or wheat or quinoa, refined grains or whole grains.

As you go forth looking at different omega-3 supplements, consider the source and what that means for the daily dose you need to consume.

* The vitamin A and D in modern cod liver oils is unfortunately reduced due to necessary refining. One tablespoon of Omega Cure, for instance, contains only 30% of the daily vitamin A recommended and only 10% of the daily vitamin D recommended.

References:
1. Halvorsen, Johannessen, Ida and Randi. Vi skal jo selge et produkt’: Oljen er produsert i anlegg som lager dyrefor – i Sør-Amerika.” Aftenposten. May 20, 2008.

2. Halvorsen, Johannessen, Ida and Randi. “Nordmenn kjøpte overpriset fiskeolje fra Sør-America for 285 millioner kroner i fjor.” Aftenposten. May 15, 2008.

3. Omega-3 Fatty Acid, Fish Oil, DHA (docosahexaenoic acid), EPA (eicosapentaenoic acid). WorldHealth.Net. American Academy of Anti-Aging Medicine. December 30, 2005.

4. Hamilton et al. Lipid composition and contaminants in farmed and wild salmon. Environmental Science and Technology. 2005 Nov 15; 39(22):8622-9.

5. Kirkpatrick, Kristin. Fish Faceoff: Wild Salmon vs. Farmed Salmon. Health Essentials. Cleveland Clinic. March 3, 2014.

6. Guy, Ruth.  The History of Cod Liver Oil as a Remedy. The American Journal of Diseases of Children. 1923; 26(2):112-116. doi:10.1001/archpedi.1923.04120140011002.

7. Kosthold for gravide. Helsedirektoratet.no. November 1, 2015.

8. Neptune at fault in deadly plant explosion, CSST rules. CBC News. May 8, 2014.

9. Burri, Lena. Optimizing the Omega-3 Index with Krill Oil. Superba Krill. Aker BioMarine.

10. Daniells, Stephen. Krill and fish oil supplements equally effetive at boosting omega-3 levels, says DSM study. NutraIngredients-USA. September 10, 2015.

11. Salem, Norman and Kuratko, Connye. A reexamination of krill oil bioavailability studies. Lipids in Health and Disease 2014; 13:137. DOI: 10.1186/1476-511X-13-137.

10. Daniells, Stephen. Krill and fish oil supplements equally effetive at boosting omega-3 levels, says DSM study. NutraIngredients-USA. September 10, 2015.

11. Salem, Norman and Kuratko, Connye. A reexamination of krill oil bioavailability studies. Lipids in Health and Disease 2014; 13:137. DOI: 10.1186/1476-511X-13-137.

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