Omega-3 fatty acids are central to the health benefits associated with seafood. Oily fish such as salmon, trout, mackerel and herring, are excellent sources of omega-3.
Omega-3 polyunsaturated fatty acids are also referred to as n-3 fatty acids. The two key fatty acids are the long chain omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Both EPA and DHA have important roles in our bodies, for example in the way cells function, in immune reactions and in the brain. The brain is a fat-rich organ, and around half of the fat content is DHA.
Polyunsaturated fats are found in more than one form. In dietary terms two main forms of fatty acids are essential, meaning they cannot be synthesised in the body. These are omega-3 and omega-6 fatty acids. The chemical difference is the position of the first double bond between atoms in the molecule, counting from the end of the carbon chain. In the omega-3 family it is between the third and fourth carbons along the chain of carbon atoms and in the omega-6 family it is between the sixth and seventh. Both forms have important functions in the human body. For example, in addition to DHA, the brain has significant quantities of the omega-6 fatty acid know as arachidonic acid.
We evolved on a diet in which omega-3 and omega-6 fatty acids were about equal. However, in recent decades that balance has shifted so that the intake of omega-6 fatty acids, from sources such as vegetable oils, is many times higher than our intake of omega-3 fatty acids. It is believed that the health benefits offered by omega-3 fatty acids are gained when these two families are brought more into balance in our diets. That can be greatly influenced by eating fish regularly.
Just one or two meals a week of oily fish such as salmon can significantly improve the ratio of omega-3 fatty acids to omega-6 fatty acids in our diets according to calculations carried out at the Marine Harvest Corporate Technical Centre.
Ideally the ratio of omega-6 fatty acids with the omega-3 fatty acids should be 5:1 or less. In typical UK diets it is around 8:1 and 10:1 in North America.
Using nutritional figures from Marine Harvest salmon and a fillet portion size of 170g, calculations show two meals a week in the US would move the total diet intake ratio to 7:1 and in the UK it would be 6:1, very close to the target. Even one meal moves the US diet to 8:1 and the UK diet to 7:1. These simple diet changes would help deliver many of the benefits associated with omega-3 fatty acids.