Understanding the science bit

Omega-3 fats are polyunsaturated fats, which can be divided into two groups – short-chain and long-chain. The body is able to convert short-chain omega-3 fats, found in foods like flaxseed, rapeseed oil, walnuts and green, leafy veg, into long-chain omega-3s but this conversion process isn’t very efficient. 

In contrast, oil-rich fish such as mackerel, salmon, pilchards, sardines, trout, kippers, herring and fresh tuna are naturally rich in long-chain omega-3 fats, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). In particular, it’s these ‘ready-made’ long-chain omega-3 fats in oily fish that have been linked to various health benefits.