Scientists at Nofima have now found that a mixture of a Norwegian plant oil and fish oil from the North-Atlantic can stimulate animals and humans to form healthy omega-3 fats themselves.

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Reidun Lilleholt Kraugerud  

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The long, healthy omega-3 fatty acids EPA and DHA are important for animal and human health. Not least for salmon, which have a lot of these in their natural diet. However, it is important that this valuable resource is utilised in the body as much as possible.

One way to increase utilisation is to stimulate farmed salmon to transform more of the short omega-3 fatty acid (alpha-Linolenic, ALA) that we find in plants, into long omega-3 fatty acids (EPA and DHA) that we find a lot of in fatty fish. Both salmon and humans have limited ability to make EPA and DHA from ALA.

Cetoleic acid as an omega-3 catalyst

Herring oil has a high level of cetoleic acid, which serves as an omega-3 catalyst. Photo: Tommy Ellingsen/Nofima.

Four years ago, Nofima scientists discovered that fatty cetoleic acid, which we find extensively in fatty species of fish such as sand eels and herring from the North-Atlantic, serves as an omega-3 catalyst. Cetoleic acid actually stimulates the conversion of the short omega-3 fatty acid ALA that plant oils are rich in, to the long and healthy omega-3 fatty acids EPA and DHA.

Effects in humans?

Scientists have innovatively mixed a North-Atlantic fish oil containing high amounts of cetoleic acid with a vegetable oil (camelina oil) rich in ALA. The scientists have tested the combination of the two oils in feed for rat, which serves as a model system for human nutrition.

“Our hypothesis is that when camelina oil and fish oil are mixed, the cetoleic acid from the fish oil has lots of ALA to work with in order to form EPA and DHA in the body”, says Astrid Nilsson, senior scientist at Nofima.

In the experiments, where up to 50 percent of camelina oil was mixed with a North-Atlantic fish oil, there was an equally high final content of the essential and healthy fatty acid DHA in the blood as there was after the ingestion of pure fish oil with high DHA content.

“This means that when you take the best of both worlds, you can use half as much of the EPA- and DHA-rich fish oil and still end up with a jackpot of DHA levels in the body”, says Nilsson.

However, the mixture ratio between available ALA and cetoleic acid will most likely be important in order to achieve the maximum amounts of EPA and DHA.

Plant oil is common in fish feed

Camelina oil contains substances that are good in feed combinations with fish oil. Today, the oil is popular on the health food market. Photo: Jon-Are Berg-Jacobsen/Nofima.

The scientists also wish to test such combinations of oils on salmon. Mixing plant oil and fish oil in fish feed is nothing new. A Nofima report from 2019 shows that from 2000 to 2016, feed producers went from not using plant oil in feed to having around 20 percent in feed. However, little is known about whether salmon benefit from an interaction between ALA and cetoleic acid in today’s commercial feed in cages in the sea.

Nofima’s senior scientist Tone-Kari Østbye has researched the mechanisms behind cetoleic acid in feeding experiments involving salmon, as well as in salmon liver cells and human cells. The results show that cetoleic acid increases the cells’ capacity to synthesize EPA and DHA from the ALA precursor.

“When we see this in human-cell trials, there is a strong indication that the same will occur in humans too. However, we can’t be certain of this until fish oil with high cetoleic acid levels is compared to fish oil with low cetoleic acid levels in human diets”, says Østbye.

The research has taken place in two projects funded by the Norwegian Seafood Research Fund (FHF) and the Research Council of Norway together with industry partners. Important industrial partners are Norsk matraps and TripleNine Group. The North-Atlantic fish oils that have been used in the trials are lesser sand eel oil and herring oil.

The results have great commercial value for the fish oil industry:

“The knowledge gained through the projects will also be of great benefit to the aquaculture industry, in terms of optimal utilisation of marine and vegetable oils, and to better manage omega-3 levels in farmed fish”, says R&D Manager Ola Flesland from the fish oil manufacturer TripleNine.

About omega-3

Omega-3 fatty acids from fish are known to contribute to good human cardiovascular health and a well-functioning immune system. And while the UN expects the world’s population to grow to almost 10 billion in 2050, the supply of fatty fish from fisheries is relatively stable. This means that less marine omega-3 will be available to each individual person than before. Therefore, people all around the world are working to increase access to marine Omega-3 and to find other sources.

About the fatty acids in the article

  • ALA = alpha-linolenic acid. Precursor to EPA and DHA. Certain oil plants are rich in ALA
  • EPA = eikosapentaenoic acid. Essential fatty acid for salmon, which marine oil sources are rich in.
  • DHA = Docosahexaenoic acid. Essential fatty acid for salmon, which marine oil sources are rich in.
  • Cetoleic acid = fatty acid found in high levels in fish from the North-Atlantic. Stimulates the transformation of ALA to EPA and DHA.


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