Fats

From a chemical point of view, fats consist largely of glycerides (or neutral fats), which in turn consist of glycerol and fatty acids (saturated or unsaturated). The type of fatty acid is particularly important, as it determines the differences in their physical and chemical properties as well as in their biological and nutritional value.

1 g of fat provides 9.3 calories and acts as a vehicle for transporting the fat-soluble vitamins A, D, E, F and K. The human body cannot synthesise the essential fatty acids linoleic acid, linolenic acid and arachidonic acid, so it is important that we take them in through food.

As far as their origin is concerned, fats can be of animal, plant or mixed origin, and each category includes types that are liquid or solid at normal temperatures.

In animals, fat is deposited in the subcutaneous tissue or around internal organs. In some species it even enters the make-up of the muscle tissue and gives it a certain tenderness (for example: pork muscle).

In plant organisms, fats accumulate preferentially in the embryo, in the fruits and in the seeds, where they are present in the form of emulsions with water and proteins.

Types of fat:

Butter is the fat from the milk of some mammal species (usually cow's milk), obtained by churning or centrifuging the cream, kneading it and then washing it. The average fat content of butter is 65-85 %. From a nutritional point of view, fresh butter has the advantage of providing lipids in emulsified form with increased digestibility. Besides lipid components with a high biological value, butter is also important for the intake of the fat-soluble vitamins A, D and E.

Lard (pork fat) is obtained by rendering subcutaneous fatty tissue (back fat) and separating out the non-lipid components. Its lipid content is very high (99-100 %), which gives it a high calorie value. Compared with other kinds of dietary fat, however, it has a low digestibility because of its high content of saturated fatty acids, whose role in the development of nutritional disorders is now being defined ever more clearly. Its indications in a rational human diet are therefore reduced.

Tallow (cow or sheep fat) is likewise obtained by rendering the fatty tissue of these animals. Rendered tallow consists almost entirely of lipids. Because of its high content of saturated fatty acids, it is hard to digest.

Poultry fat (duck, goose, turkey, chicken) has a characteristic yellow colour. Unlike mammal fat, it has a lower content of saturated fatty acids. Because it has a higher proportion of unsaturated fatty acids (oleic acid, linoleic acid and so on) than the fat of other species, poultry fat has a higher nutritional value and is easier to digest.

Fish fat is obtained by rendering the raw fat directly or with the help of steam. It has a high content of the fat-soluble vitamins A and D as well as of unsaturated fatty acids, which gives it an increased nutritional value and good digestibility.

Vegetable oils are obtained by extraction from various parts of plants where they are more commonly stored, namely from: the embryo (maize or wheat germ oil), fruits (olive oil, walnut oil) or seeds (safflower, sunflower, soya, pumpkin, sesame oil), which are called oilseeds precisely because of their high lipid content. The technological process for producing vegetable oils involves pressing or extraction (or both) on the one hand and refining on the other. The end product obtained has excellent organoleptic properties, better keeping qualities and a high lipid content (99 - 99.7 %). Because of their high energy intake, the vital nutrients they provide to the body (polyunsaturated fatty acids) and their high digestibility, vegetable oils occupy an important place in human nutrition, and their share rises to 1/3 to 1/2 of the daily lipid intake. Because of the elaborate industrial processing, the end product contains no vitamins, or only very small amounts.

Margarines are, by origin, mixed fats, produced synthetically from mixtures of high-quality animal fats (butter) and vegetable oils, to which milk, egg yolk, salt, carotene and various flavourings are added. In appearance, taste and smell, margarines resemble butter.

Fats give food palatability and a feeling of fullness and have no influence on insulin production (GL=0). From a physiological point of view they play a structural and functional role, since, besides their energy function, they also take part in the make-up of cell membranes and play a paracrine and endocrine role by producing some hormones.

Healthy fats

are those with a balanced ratio of Omega-3 to Omega-6 fatty acids (ideally 1:1-4; today the ratio is heavily distorted and stands at 1:17-23) and monounsaturated fats (Omega-9 oleic acid – from olive). and rapeseed oil). The group of long-chain Omega-3 fatty acids includes docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), which occur in oily fish from cold sea areas (wild salmon), cod, tuna, hake, mackerel, sardines and seafood , and the group of short-chain Omega-3 acids includes linolenic acid (ALA), which occurs in foods of plant origin (green vegetables, nuts, linseed, linseed oil, rapeseed oil) and which the body has to convert into long-chain Omega-3 acids. chain fatty acids (EPA and DHA).

The polyunsaturated fatty acids Omega-3 (ALA – alpha-linolenic acid) and Omega-6 (LA – linoleic acid) cannot be synthesised in the body; they have to be taken in through food and are indispensable for good health, but the ratio between them is of the greatest importance .

Human metabolism can convert ALA into EPA and DHA by desaturation and elongation, but only under conditions of a low Omega-3/Omega-6 ratio that lies within optimal values. Since both metabolic pathways for converting Omega-3 and Omega-6 use the same desaturating enzymes, there is competition between the biosynthesis of fatty acids with a positive effect and those with a negative effect (arachidonic acid, AA), in favour of the latter .

As we get older, the enzyme systems that convert ALA into EPA and DHA become less and less efficient, which increases the need to take them in directly through food, either through products rich in the two essential fatty acids or through food supplements.

Alpha-linolenic acid (ALA) is an essential omega-3 fatty acid: the body cannot make it itself. It is needed for the growth and development of children, contributes to the maintenance of normal blood cholesterol levels (with a daily intake of 2 g) and is the starting point for the long-chain omega-3 fatty acids EPA and DHA.

From EPA the body makes messenger substances (eicosanoids) that are involved in regulating inflammatory reactions and blood clotting. Linoleic acid (LA) is converted in the body into arachidonic acid (a component of cell membranes), from which prostaglandins (PGE2) are formed. In low concentrations they are needed for the normal function of the immune system; persistently high concentrations, on the other hand, are associated with chronic inflammatory processes.

The most important biological functions of essential fatty acids are:

• functional components: membrane phospholipids, regulators of membrane fluidity, regulators of the enzyme functions associated with cell membranes.
• Structural components: phospholipids are the main components of all cell membranes, lipid transporters, precursors of important biological mediators; in excess they can be used as a source of energy.

Dangerous fats

are rich in atherogenic saturated fatty acids:

• saturated animal fats from: fat and fatty meat, butter, full-fat cheese;
• hydrogenated and partially hydrogenated vegetable oils: industrial margarines with a high content of trans fatty acids, processed foods, biscuits, snacks, crisps, pastries, confectionery;
• an excess of vegetable oils rich in Omega-6, from: maize, safflower, sunflower, processed foods;
• trans fatty acids contained in hydrogenated and partially hydrogenated oils, processed foods, fast food, pastries, biscuits, popcorn;

Depending on the configuration of the double bonds, fatty acids form spatial CIS-TRANS isomers. In unsaturated fatty acids the two hydrogen atoms lie on the same side of the carbon double bond and form CIS isomers, which occur in most dietary fats. CIS fatty acids determine normal biological structures and ensure the correct working of the metabolism and the state of health.

TRANS isomers are created by the industrial hydrogenation of fats, which become more uniform (spreadable) at room temperature and more resistant to oxidation.

The trans acid most widespread in foods is elaidic acid, which is harmful to health; its counterpart is oleic acid.

Clinical and epidemiological studies have shown that a high intake of TRANS fatty acids through food, more than 2 g a day, is linked to the risk of coronary heart disease, cancer, neurodegenerative diseases and other chronic illnesses. These effects would be due in part to the fact that TRANS fatty acids change the fluidity of cell membranes, stiffening them and preventing them from working properly. On the other hand, TRANS fatty acids inhibit the desaturation and elongation processes of linoleic and linolenic acid, from which the long-chain essential fatty acids (DHA; EPA) arise that are indispensable for the normal development of the brain and the organs.

Eating trans fats above 2 g a day leads to them building up in the cells involved in regulating the heart rhythm and considerably increases the risk of heart rhythm disorders, by a factor 10 higher than with ordinary saturated fats.

Studies have shown that trans fats also contribute to insulin resistance in type 2 diabetes, encourage and maintain a systemic inflammatory state and increase the risk of breast and bowel cancer, allergic diseases, rhinitis, atopic conditions and asthma.

In pregnant and breastfeeding women, trans fats reduce the bioavailability of essential fatty acids in the blood and in breast milk (they pass into the breast milk and reach the baby), which leads to the birth of babies with a low birth weight and a small head circumference.