The Omega-3s are now recognised as valuable nutrients in a healthy diet.  The important Omega-3s are: ALA, EPA and DHA.  ALA is alpha-linolenic acid, an essential part of a healthy diet because, like essential vitamins, it cannot be made in the body. 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 (for example in breast milk and circulating in the blood) is to eat preformed DHA.

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 offal foods 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 offal.  Modern farming practices have led to a reduction in DHA levels of eggs and meat and we now eat too much of 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.

Omega Balance

Omega-3s and Omega-6s are both important polyunsaturated fats in the diet.  In most Western diets we eat way too many Omega-6s and experts recommend that we should aim to improve our Omega-3 to Omega-6 balance by increasing Omega-3 intake.  The most efficient natural source of pre-formed DHA and EPA is oily fish such as tuna, mackerel, sardines, herring and salmon.  Tuna oil is particularly interesting in that it contains a five to one ratio of DHA to EPA, which is similar to the ratio found naturally in human breast milk.

One of the reasons to keep a healthy balance of Omega-3s and Omega-6s is that they tend to have opposing effects within the body and actually compete for the necessary enzymes to supply the body with the specific optimal compounds produced directly or indirectly from these fatty acids.