The main brick of fats are fatty acids, formed from a chain having two to thirty carbon atoms and a carboxylic acid terminal group CH3 – (CH2) n COOH.
Fatty acids can be classified in two ways:
a) by the length of the chain and talk about
– short-chain fatty acids (4-6 carbon atoms)
– medium-chain (8-12 carbon atoms)
– long-chain (14 carbon or several more atoms)
b) by the degree of unsaturation. Each carbon atom has four valences; two are used for the formation of the chain, and the rest of the valences are occupied by hydrogen atoms, so when there are no double links, we talk about a saturated fatty acid (as in the case of all seats occupied in the bus). When two carbon atoms are joined only by two hydrogen atoms, it is formed a double link, and the fatty acid is unsaturated. If there is only one double link, we say that a is monounsaturated fatty acid. When there are two or more double links, then the fatty acid it is polyunsaturated.
In nature there are over 40 different fatty acids. Depending on the geometric configuration, acids can have the form CIS or TRANS. CIS fatty acids have those two hydrogen atoms on the same side of the molecule. In natural state, mostly unsaturated fatty acids have CIS configuration. TRANS acids have hydrogen atoms on the both sides of the molecule. This configuration occurs when unsaturated vegetable oils are partially hydrogenated to produce margarine or a kind of sauce used to prepare various foods (shortenings). During the solidification process, the double link of CIS fatty acids is converted to TRANS. Vegetable fats
processed this way can contain 5-30% TRANS isomers. By bacteria action TRANS isomers are formed in the rumen of ruminants (first part of their stomach) forming about 5% from dairy and beef fat.
Although some unsaturated fatty acids are the same regarding the carbon chains length, the number of double links and geometric configuration, they can be different if the double links are located in different positions of the carbon atoms chain. The position of the first double link, starting from the methyl end of the carbon chain is specified by “n” or “ω” (omega, the last letter of the greek alphabet). Most unsaturated fatty acids enter in three main groups, namely: n-3, n-6 and n-9. E.g: 18: 1 n-9 is oleic acid, where the number 18 shows the total number of carbon atoms, 1 shows the number of unsaturated links (ie a single double link) and n-9 indicates that the first link is localized in the 9th carbon atom from the methyl end.
When the energy intake is low, such in fasting or during strenuous activities, fatty acids are mobilized in the fat tissue to meet the energy needed. In the heart and in the skeletal muscles, fatty acids are activated acyl-coenzyme A, being transported to the mitochondria, the energy factories of the cells, where they are oxidized into acetyl-coenzyme A, which enters the Krebs cycle and forms adenosine triphosphate (ATP) for muscle activity.
Fatty acids are also components of cell membranes, being inside the double layer composed of phospholipids. Physical properties of the cell membrane pertain to the composition of the fatty acids from phospholipids. Diet rich in polyunsaturated fatty acids and especially linoleic acid, which forms 70% of sunflower oil, makes that this oil to be easier attacked by oxidising agents.
Fatty acids are also the precursors of some metabolites are biologically active, as eicosanoids, prostaglandins, leukotrienes and thromboxane. Also carries fat-soluble vitamins (A, D, E and K), during their absorbtion in the small bowel.
Animal fats, as bacon, the abdominal cavity fat and butter contain large amounts of saturated fatty acids (lauric, myristic palmitic and stearic acid), with 12, 14, 16 and 18 carbon atoms.
Saturated fatty acids can be synthesized in the human body, reason why is not an essential part of alimentation. Usually, saturated fats have a solid consistency at room temperature. Over 66% of fat in dairy products consists of saturated fat. Tropical oils, from coconut and palm contain about 80% saturated fat. These fats are often used in commercial preparations, because they resist oxidation and extend the products life on the shelves.
Lauric saturated acids (CH3 (CH2) 10 COOH), myristic (CH3 (CH2) 12-COOH) and palmitic (CH2- (CH2) 14-COOH), which are found in the dairy products significantly increase the blood cholesterol. Palmitic acid is synthesized fatty acid in the body from the excess calories converted into fat. Of all fats consumed, the most hypercholesterolemia action have coconut, palm oils and butter.
Saturated fatty acids increase the low density lipoprotein (LDL or “bad” cholesterol) lowering LDL receptor synthesis and their activity. In the past, for lowering the cholesterol is recommended the intake of polyunsaturated fatty acids. Today, we know that the decrease of saturated fatty acid consumption, ie dairy products fats and other foods of animal origin, is two times more effective than the intake of polyunsaturated fatty acids.
Replacing the sugar, honey and other sweets in the alimentation with starch (bread, brown rice, polenta, boiled cereals), decreases the synthesis of fatty acids and, indirectly, the cholesterol.