The amount of omega-3 in farmed salmon has halved in the past decade, according to a study carried out at Stirling University.
The researchers, led by Professor Douglas Tocher, found that a 130g portion in 2006 contained 3.5g of omega-3, whereas the same portion size in 2015 contained half that amount.
This is because salmon are being fed fewer smaller fish following complaints over sustainability by environmental groups. In 2006, the average salmon’s diet was 80 per cent oily fish, compared with 20 per cent today.
The study, published in the journal Scientific Reports, involved an analysis of 3,000 farmed salmon specimens over a nine-year period.
Professor Tocher said: ‘Ten years ago people were complaining about the level of marine ingredients in salmon feed,’ he said.
‘Now, the majority of materials in feed are plant-based – it’s the complete opposite. The consequence of this is the level of omega-3 will go down.
‘I don’t want this to sound negative. Despite everything, farmed salmon is still the best source of long chain omega-3s. Even with the fall, they still have more than wild salmon.’
This is a well-designed study which documents a statistically significant reduction in the amount of omega-3 oils available to us from farmed salmon due to modern farmed-fish feeding methods. The methodology and statistical analysis seem robust and very clearly articulated. The authors (who declare no competing financial interests) suggest that in order to obtain the same amount of omega-3 oils we did 10 years ago from farmed salmon we would need to double our intake of it.