ESSENTIAL FATTY ACIDS
Fatty acids are the building blocks of fats; they are "essential" because we need them to live, yet we cannot manufacture our own, instead we must ingest them through the foods we eat. There are two main subtypes of essential fatty acids (EFAs): the Omega-3 and Omega-6 fatty acids. The Omega-3s are found in cold water fish (e.g., mackerel, herring, tuna) and in most nuts. The Omega-6's can be obtained from plant sources such a Evening Primrose, Borage and Flaxseed oils.
All EFA's are polyunsaturated; they have carbon bonds that are easily broken and do not result in harm to the body. However, when EFA's are heated, their bonds change and they become the "sticky" and "harmful fats" known trans fatty acids (TFAs). These are the type of fats found in many deep fried foods common in the "typical American diet."
OMEGA-3 FATTY ACIDS & DEPRESSION
Omega-3 essential fatty acids tend to be systematically removed from our food supply in order to improve its shelf life, and must be re-supplemented. An insufficiency of omega-3 oils (especially an essential fatty acid known as DHA [decosahexanoic acid]) in the diet has been linked to depression.
This may be related to the impact of dietary fatty acids on the composition of nerve cell membranes. While it is thought that the cell is programmed to selectively incorporate the different fatty acids it needs to maintain optimal function, a lack of essential fatty acids (particularly the omega-3 oils) and an excess of saturated fats and animal fatty acids leads to the formation of cell membranes that are much less fluid than normal.
A relative deficiency of essential fatty acids in cellular membranes substantially impairs cell membrane function. Since the basic function of the cell membrane is to serve as a selective barrier that regulates the passage of molecules into and out of the cell, a disturbance of structure or function disrupts the cell's ability to control its internal environment.
Because the brain is the richest source of fatty acids in the human body, and because proper nerve cell function is critically dependent on proper membrane fluidity, alterations in membrane fluidity impact behavior, mood, and mental function.
The current recommended daily intake of DHA is 200mg.