The health benefits associated with the consumption of salmon are well known. In addition to being an excellent source of protein, vitamins and minerals, salmon represent one of the few major sources of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the human diet. Adequate intake of both these beneficial omega-3 fatty acids has been shown to significantly reduce the risk of cardiovascular disease and improve cognition.
Additional potential health benefits of omega-3 fatty acids include protection against rheumatoid arthritis, Alzheimer’s disease, depression and even some types of cancer. Notwithstanding, most people still fail to meet the recommended daily intake levels; furthermore, beneficial omega-3 levels in farmed fish are in decline ― mainly due to the increasing use of vegetable oils in fish feed.
These oils partially replace the conventional ― and now scarce ― fish oils; however in contrast to fish oil, contain hardly any EPA and DHA. Is it, therefore, desirable to increase the levels of EPA and DHA in fish feed and recent research has shown that this is possible by including seaweed in the salmon diet.
From seaweed to salmon
Research reveals that most seaweed contains substantial amounts of beneficial omega- 3s. Although the total fat content of seaweed is low, comprising only 1-5% of the dry weight, EPA + DHA levels can make up more than half of the total lipid profile.
OceanFeedTM (a proprietary blend of specially selected seaweeds, manufactured by Ocean Harvest Technology in Milltown, Co Galway) is included in the salmon diet at an inclusion range of 10- 15% and has been shown to significantly increase the EPA and DHA content of the feed. Any such changes in dietary lipid level should be reflected by the lipid profile of the fish flesh and, for the first time, Ocean Harvest Technology is investigating this.
In our research facility in Milltown we are determining the EPA and DHA levels of salmon from two different trials. The first trail, with Atlantic salmon in Scotland, was carried out with an organic salmon diet containing 100% fish oil and 0% vegetable oil.
Our analyses show a 9% increase in EPA and DHA in the salmon lipid when seaweed was included in the fish diet at 15%. The total lipid contents of seaweed-fed fish are also higher, resulting in a total 25% increase in the level of the beneficial omega3 fatty acids.
We are also in the process of completing another study to confirm if OceanFeed™ can improve the omega-3 fatty acid profile of fish that are fed on a high (70% inclusion) vegetable oil diet which resembles the diet of most farmed fish. Preliminary results from this second study are promising, indicating an even larger difference between the control and OceanFeed™ group.
Possible impact on human health
The most well studied and established effect of EPA and DHA is their prevention of cardiovascular diseases. For instance, intake of 250 mg per day of EPA + DHA can prevent 7,125 cases of stroke, myocardial infarction and cardiac death in every 100,000 people. As EPA and DHA levels in farmed fish are decreasing, it will get even more difficult for the general population to meet this adequate omega-3 intake.
So far, it looks like seaweed is capable of accounting for the loss of these beneficial omega-3 fatty acids in farmed salmon, and may even cause the levels of EPA and DHA in vegetable oil-fed salmon to exceed those present in salmon that are fed on fish oil alone.
Therefore, the inclusion of OceanFeed™ ― a wholly sustainable and fully natural feed ingredient― in the diet of farmed salmon has huge potential for improving human health.