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Lipids
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| Lipids do not have a good reputation: accused of causing cardiovascular diseases, obesity or, in the best of cases simply unpleasant aesthetic consequences, they are often banished from diets. In actual fact however they carry out important functions in the human body, and it would be a mistake to underestimate their properties. |
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From the chemical point of view, lipids are triglycerides, phospholipids and sterols, substances that are not water soluble and which can be dense (fats) or liquid (oils), formed from the union of glycerine with fatty acids. They can have a number of functions, from the body's energy reserve, accumulating in the layer of adipose tissue, to biological ones (some hormones are lipids, for example, and lipids are the vehicles for a number of vitamins, which are therefore known as liposoluble). Generally a distinction is made between simple lipids, present in both man and foods, and complex lipids that are present in plasma and cell structures both of animal and vegetable origin. According to the links in the chain of fatty acids that they are composed of, there are saturated fatty acids (butter or lard), monounsaturated (olive oil) and polyunsaturated (soy oil).
Nutritionists recommend that lipids should account for about 25% of the total calories, favouring unsaturated vegetable origin fats, which contain a smaller amount of cholesterol. Yet the percentage of lipids present in the diet usually varies from country to country, being higher in richer countries (35-45%) and far lower in poorer countries (10-15%). Where more vegetable fats are traditionally consumed such as in Japan and southern Italy, there is a lower presence of thrombosis and heart attacks: these types of fats actually fortify the arteries, protecting them against increases in blood pressure whilst normalising the metabolism of sugars. Consequently it is far from recommendable to eliminate lipids from the diet. To maintain a steady weight, it is in fact necessary to just reduce the amounts, consuming primarily the types that guarantee a positive effect on the body.
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It is therefore a good rule of thumb to consume vegetable oils, starting with olive oil but including those made from soy, peanuts, walnuts, cotton seeds, sunflowers, rape and corn, which are easily digestible in spite of their high energy values and contain a good quantity of vitamins. Another condiment which is widespread and full of vitamins is butter, particularly valued in cooking in the regions of the north of Italy. It is however necessary to pay attention to its quality: its properties alter easily as it contains water and protein residues. The best way to store it is to keep it in a hermetically sealed box in the fridge, far fro heat sources as well as light and air. It is also better to eat it raw, as it is easier to digest.
The decision to cook this substance or otherwise should not be taken lightly: at moderate temperatures its digestibility is increased slightly, whilst high temperatures reduce it drastically. It is thus also necessary to distinguish between those animal fats which are more or less necessary for the body: in particular, the Omega 3 and Omega 6 fatty acids, contained principally in fish are the most important, as they maintain the cell membranes elastic and limit the formation of free radicals.
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