Herring has a naturally high content of cetoleic acid, a fatty acid whose importance we haven’t previously been aware of. We now know, however, that it has properties that promote health. Senior scientist Bente Ruyter and her colleagues at the food research institute Nofima, have carried out experiments showing that cetoleic acid stimulates cells to convert short omega-3 fatty acids into the healthy, longer marine omega-3 fatty acids.

The experiments used human liver cells and liver cells from salmon. Both of these showed that pure cetoleic acid stimulates increased formation of the healthy, longer marine omega-3 fatty acids. 

Cetoleic acid added to feed causes the salmon to store 10% more marine omega fatty acids (EPA and DHA) in the body than they do otherwise.

Other rich sources of cetoleic acid are sand eels and capelin, in contrast to oily fish from South America, such as sardines. The latter have very low levels of cetoleic acid, while having much higher levels of EPA and DHA.

The results of the feeding experiments show that salmon fed with herring oil, acquired higher deposits of EPA and DHA in the body than fish fed with South American sardine oil.

The scientists also saw lower levels of the condition known as “fatty liver” in farmed fish that had been given herring oil in their feed.

“Salmon that had been given herring oil had less fat in the liver, which suggests that they had a higher level of fat metabolism. This is good for the salmon,” said Ruyter.

The research was financed by the Norwegian Seafood Research Fund (FHF).