Omega-3 fatty acids are now recognized as a valuable nutrient in a healthy diet. Omega-3s comprise a group of fats know as essential fatty acids (EFAs). These are termed “essential” because the body cannot synthesize them in adequate quantities, and they are vital for life. The three main Omega-3s are: Alpha linolenic acid (ALA), eicosapentaenoic acid (EPA) and (docosahexaenoic acid (DHA).
ALA comes from vegetable sources, such as walnuts and green vegetables, and especially certain vegetable oils including linseed (flaxseed) oil, and canola oil. ALA can be converted in the body to EPA then to DHA but the process is inefficient and only a small proportion gets as far as DHA. This small proportion may be sufficient to supply brain cells in many individuals, especially since brain cells seem to be good at retaining the DHA they need even when blood levels are falling. But, there is no doubt that the most effective way of increasing general tissue stores of DHA is to eat pre-formed DHA either in food or in supplement form.
DHA and EPA are the long chain Omega-3s we get from eating oily fish such as mackerel, herring, sardines, salmon and fresh tuna. You can also get small amounts of DHA from some animal products, particularly organ meats such as liver and kidney.
But intakes of DHA and EPA have declined in the UK and other countries with a western diet over the last fifty years. This is shown by levels of DHA in breast milk, which are much lower than they used to be. We are eating less fish and organ meats. Modern farming practices have led to a reduction in DHA levels of eggs and meat and we now eat too much food that is high in another omega family the Omega-6s (e.g. from sunflower & soya bean oils). Experts now advise us to redress the balance and eat more Omega-3s including DHA.