<P> The' essential' fatty acids were given their name when researchers found that they are essential to normal growth in young children and animals . The omega − 3 fatty acid DHA, also known as docosahexaenoic acid, is found in high abundance in the human brain . It is produced by a desaturation process, but humans lack the desaturase enzyme, which acts to insert double bonds at the ω and ω position . Therefore, the ω and ω polyunsaturated fatty acids cannot be synthesized and are appropriately called essential fatty acids . </P> <P> In 1964 it was discovered that enzymes found in sheep tissues convert omega − 6 arachidonic acid into the inflammatory agent called prostaglandin E which both causes the sensation of pain and expedites healing and immune response in traumatized and infected tissues . By 1979 more of what are now known as eicosanoids were discovered: thromboxanes, prostacyclins, and the leukotrienes . The eicosanoids, which have important biological functions, typically have a short active lifetime in the body, starting with synthesis from fatty acids and ending with metabolism by enzymes . If the rate of synthesis exceeds the rate of metabolism, the excess eicosanoids may, however, have deleterious effects . Researchers found that certain omega − 3 fatty acids are also converted into eicosanoids, but at a much slower rate . Eicosanoids made from omega − 3 fatty acids are often referred to as anti-inflammatory, but in fact they are just less inflammatory than those made from omega − 6 fats . If both omega − 3 and omega − 6 fatty acids are present, they will "compete" to be transformed, so the ratio of long - chain omega − 3: omega − 6 fatty acids directly affects the type of eicosanoids that are produced . </P> <P> Humans can convert short - chain omega − 3 fatty acids to long - chain forms (EPA, DHA) with an efficiency below 5% . The omega − 3 conversion efficiency is greater in women than in men, but less studied . Higher ALA and DHA values found in plasma phospholipids of women may be due to the higher activity of desaturases, especially that of delta - 6 - desaturase . </P> <P> These conversions occur competitively with omega − 6 fatty acids, which are essential closely related chemical analogues that are derived from linoleic acid . They both utilize the same desaturase and elongase proteins in order to synthesize inflammatory regulatory proteins . The products of both pathways are vital for growth making a balanced diet of omega − 3 and omega − 6 important to an individual's health . A balanced intake ratio of 1: 1 was believed to be ideal in order for proteins to be able to synthesize both pathways sufficiently, but this has been controversial as of recent research . </P>

Which of the following is a good source of omega-3 fat