In turn, unsaturated fatty acids are indicated with the term "omega", followed by a number relating 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 three;
- Omega six.
As you will recall, the "essentiality" of a nutrient for a species derives from the "inability of organisms to produce it. The alpha-linolenic acid of the omega three series and the" linoleic acid of the omega six series are essential fatty acids, from which the organism synthesizes other semi-essential derivatives - which can however also be found in foods.
The various omega three and six fatty acids, despite having a very similar chemical structure, have often distinct properties and above all physiological functions.
Deficiency of essential fatty acids produces severe deficiency manifestations in humans due to the fact that these nutrients not only have structural functions (cell membrane), but are precursors of prostaglandins, prostacyclines and leukotrienes - which we will see below.
packaged) and, more in depth, in farming technologies - which favor grain-based feed rich in omega-6 and low in omega-3.Even in fish - which are the primary source of some EPA and DHA (see below) in the human diet - farmed fish fed with poor quality pellets have a lower omega-three content than caught fish - as the latter is naturally nourishes.
The marine plants, but above all the unicellular algae present in the phytoplankton, can effect a further elongation and desaturation of the alpha-linolenic acid, giving rise to the eicosapentaneic acid (EPA) and to the docosahexaenoic acid (DHA).
Their incorporation into membrane phospholipids increases fluidity, therefore erythrocyte flexibility, with an improvement in the hemorheological properties of the blood.
Furthermore, polyunsaturated fatty acids play an important biological role, as, by becoming part of the structure of cell membranes as precursors of prostaglandins and other eicosanoids (such as thromboxanes and leukotrienes) - in turn they intervene in numerous functions, including platelet aggregation, vasodilation and inflammation.
They are also endowed with metabolic functions, as regulators of lipid turnover and in particular of cholesterol transport.Finally, some polyunsaturated fatty acids limit the levels of triglycerides, inhibiting their hepatic synthesis.
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 certain 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 linked to the membrane itself; also the transport of electrons in the respiratory chain seems to be conditioned by their presence in the mitochondrial crests.
On the basis of these assumptions, the importance of an adequate intake of polyunsaturated fatty acids in human nutrition appears clear.
, dermatitis, peeling, dryness);Deficiency symptoms related to functional role include:
- alterations in the transport of lipids and cholesterol;
- slowed hepatic catabolism of cholesterol;
- alterations in prostaglandin biosynthesis;
- abnormal clumping of thrombocytes;
- hypertension;
- reduction of myocardial contractility.
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