Polyunsaturated fatty acids – Essential fatty acids
Polyunsaturated fatty acids have two or more double links, ie at least two carbon atoms are not saturated with hydrogen atoms. They’re of fluid consistency at room temperature, but also at lower temperatures. The main sources of polyunsaturated fatty acids are: vegetable oils, the seeds, cereals, vegetables and other plant foods. There are many polyunsaturated acids, the most frequently encounter are the linoleic acid with two double links, an omega-6 fatty acid and alpha-linolenic acid, with three double links, an omega-3 fatty acid.
Animals and humn can prolong the saturated fatty acid chains in unsaturated fatty acids. This is achieved by the chains desaturation of fatty acids, ie by removing an hydrogen atom. But can’t achieve this desaturation in position 6 and 3. Since the linoleic acid and alpha-linolenic acid are unsaturated in these positions, they can not be manufactured from other fatty acids and must
Be obtined from food, therefore having the name of essential fatty acids. Linoleic and alpha-linoleic acid are essentials components of cell membranes, serving as preliminary stages of a group of molecules known as prostaglandins.
Arachidonic polyunsaturated fatty acid with 20 carbon atoms and four double links, an omega-6, was originally considered as essential, but because can be synthesized from the linoleic fatty acid is no longer considered essential.
The human body does not need large amounts of essential fatty acids. It is enough if these represent 1 to 2% of the total caloric intake.
To be absorbed, foods are lose in the digestive tract, into their component parts. Since fats do not dissolve in water, digestion and absorption are different from the other nutrient substances. First, the fats must be emulsified, which occurs with the help of lecithin and bile salts from the intestinal contents. Thus, fats are lose into small particles, which can be attacked by the enzymes called lipases. Under the action of lipases, fat is loosened in fatty acid monoglycerides and diglycerides.
By the action of bile continuation, smaller drops are formed, called micelles, which contain: bile and bile salts, monoglycerides, fatty acids and glycerin.
After their absorption in the intestinal epithelial cells are again converted into triglycerides, which, long with phospholipids forms particles covered with a layer of protein, known as hylomicrons. About 80% of chylomicrons reach the lymphatic system, and that serves as a filter to remove harmful substances and microbes before the fatty acids to reach the sanguine current.