Edited by Sasha Sofo
The fatty acids are classified from a chemical point of view in saturated, monounsaturated and polyunsaturated, based on the absence or presence of one or more double bonds in the molecule.
In turn the unsaturated fatty acids are indicated with the word "omega", followed by a number relative to the position of the first double bond starting from the terminal methyl. Depending on this position, the polyunsaturated fatty acids are in turn divided into two distinct families:
-Omega 3
-omega 6
As you will remember "the essentiality" of a nutrient for a species derives from the inability of organisms to produce it. In the human species this happens for the fatty acids of the omega-3 and omega-6 series, which must therefore be taken with the diet. These two types of fatty acids, despite having a very similar chemical structure, have properties and above all clearly distinct physiological functions.
In general, the fatty acids present in the body can be of exogenous origin (brought by the diet) or endogenous (synthesized ex novo in the liver and in adipose tissue starting from precursors such as sugars and amino acids). In humans, however, the synthesis is limited to saturated and monounsaturated fatty acids (such as oleic acid), because it does not have enzymes capable of inserting double bonds at a distance equal to or less than six carbon atoms from the methyl end.
The deficiency of essential fatty acids produces serious deficient manifestations in man due to the fact that these nutrients not only have plastic functions, but are precursors of prostaglandins, prostacyclines and leukotrienes. These fats, therefore, are defined essential in humans, since, as for vitamins and certain amino acids (essential amino acids), it is not able to synthesize them even though they are absolutely necessary.
Currently the man's diet is very rich in omega-6 and poor in omega-3, in fact the ratio is around 20: 1 in favor of omega-6. The reasons are to be found in breeding technologies, which favor cereal-based foods rich in omega-6 and poor in omega-3. Also in farmed fish the presence of omega-3 is lower than in the caught fish, as the latter feeds mainly on phytoplankton; the breeding one, on the other hand, is often fed with vegetable flours (such as soy flour) with a consequent increase in omega-6 concentrations in meat. The marine plants and especially the unicellular algae present in the phytoplankton, can carry out a further elongation and desaturation of the alpha-linolenic acid, giving rise to eicosapentanoic acid (EPA) and docosahexaenoic acid (DHA).
Many studies show that these precious omega-3s can: lower blood pressure, alleviate common skin diseases (such as eczema and psoriasis), attenuate inflammatory states (such as arthritis) and support brain development. Their incorporation in membrane phospholipids increases fluidity, and therefore erythrocyte flexibility, with an improvement in the hemoreological properties of the blood. Furthermore, polyunsaturated fatty acids play an important biological role, since, becoming part of the structure of cell membranes as precursors of prostaglandins and other eicosanoids (such as thromboxanes and leukotrienes), they perform plastic functions; finally, they have metabolic functions, as regulators of lipid turnover and in particular of cholesterol transport.
The cell membrane has a lipoprotein composition which gives it a selective permeability to the passage of metabolites, but which, for this reason, must meet some requirements that affect its fluidity (an essential element to allow these passages).
In addition to increasing membrane fluidity, polyunsaturated phospholipids intervene in the activation of enzymes bound to the membrane itself; also the transport of electrons in the respiratory chain seems to be conditioned by their presence in mitochondrial ridges.
A further, important, function of membrane phospholipids is to constitute the substrate for the production of prostaglandins, which in turn intervene in numerous functions, including platelet aggregation, vasodilation and inflammation. Lastly, polyunsaturated fatty acids limit cholesterol levels, inhibiting hepatic synthesis and favoring their elimination through the biliary tract (with an action contrary to that of saturated fatty acids). Based on these assumptions, the importance of an adequate intake of polyunsaturated fatty acids in human nutrition is clear.
The essential fatty acid deficiency symptoms related to the structural role include:
- skin abnormalities (hyperkeratosis, dermatitis, scaling, dryness)
-reduction of tissue regenerative capacity
- increased permeability and capillary fragility
- increased susceptibility to infections
- mitochondrial swelling
Deficiency symptoms related to the functional role include:
- alterations of lipid and cholesterol transport
- slowed hepatic cholesterol catabolism
- alterations in the biosynthesis of prostaglandins
- abnormal thrombocyte aggregation
-hypertension
-reduction of myocardial contractility.
