Basically, there are three types of fats in the food we eat - saturated fats (generally from meat sources), polyunsaturated fats (from fish, nuts, seeds and vegetable cooking oils) and monounsaturated fats (eg from olive oil). Most experts now agree that saturated fats should make up no more than one third of our total fat intake and that polyunsaturated fats should make up at least one third.
Omega 6 and Omega 3 are what is known as the two essential fats and come from foods with high per centage of polyunsaturated fats. Omega 6 and Omega 3 are essential because when they are broken down in the body, they produce linoleic acid (LA) and alpha-linolenic acid (ALA) respectively both of which are crucial to the development of cell membranes.
The problem now, according to some nutritionists is that we have an incorrect balance of Omega 6 and Omega 3 in our diet. Some argue that many people now have up to 15 times more Omega 6 to Omega 3 in their diets due to increased consumption of vegetable oils and blended fat spreads (which are high sources of Omega 6). This results in competition for enzymes during the breakdown of Omega 6 and Omega 3 to their essential fatty acids, LA and ALA.
Those who are promoting the use of Omega 6 and Omega 3 food supplements suggest that the further breakdown of Omega 3 from ALA to DHA (docosahexaenoic acid, a long chain fatty acid) is interrupted by the concurrent breakdown of Omega 6 from LA to AA (arachidonic acid, another long chain fatty acid). These long chain fatty acids are now believed to be so important for brain development that they have recently been added to baby milk formula. The essential fatty acids, LA and ALA are already included in many baby milk formula. All four are present in breast milk.
Those promoting Omega 6 and Omega 3 food supplements claim that the food supplements contain both the Omega 6 and Omega 3 essential fatty acids and the long chain fatty acids in a correct balance. Those who believe it is better to get the nutrients from diet, suggest correcting the imbalance by eating two portions of oily fish per week for adequate Omega 3 consumption and reducing the amount of vegetable oils high in Omega 6 (such as sunflower and corn oil) as part of a overall balanced diet.