Generalities and distribution in nature ô Classification ô Fats in foods: nutritional value ô Unsatured fatty acids as nutritional lipid lowering elements ô Symptoms of fat deficiencies

Generalities and distribution in nature

With the generic term of "fats" (or lipids) we define a  group of substances which are insoluble in water but soluble in the so called organic solvents such as ether, chloroform, acetone, benzene etc.

What is particularly important, among their physical properties is the melting point at which fats are  differentiated as "solids at room temperature" and oils as "liquids at room temperature".

Fats have a specific low weight, they are hydrophobic and have low surface tension which is why they tend to form emulsions (mayonnaise is an emulsion; it includes two non-mixable ingredients: oil and water).  The biological properties are largely traced to the structure and to the type of chemical link that are present in the fatty acid molecules, and the spatial structure of the molecule.

Through chemical reactions, the double links or un-saturation present in the molecule can  undergo a hydrogenation or incorporate oxygen.  In the first case, fats become unsaturated (margarine is a fat derived from partially saturated vegetable oil), while in the second case, oxidation produces rancidity.  Auto-oxidation of fats is favoured by exposure to light and air, but it can be prevented by some anti-toxins including vitamin E.

Classification

They are distinguished as:

Simple fats

Complex fats

Fats in foods: nutritional value

The optimal proportion of lipids in a diet with a quantitative prevalence given to those of  vegetable origin  should be equal to 30% of total calories for infants, children and pre-adults and comprise 20-25% of  the daily calories consumed by adults.

The presence of an adequate portion of fats in a diet is vitally important for health as they supply essential fatty acids and fat soluble vitamins.

They represent excellent  energy nutrients: 1 g. of fat  supplies 9 calories.

A significant health  problem is tied to the consumption of animal fats; an excessive amount causes an increase of a chemical compound known as cholesterol.

Unsatured fatty acids as nutritional lipid lowering elements

The high levels of cholesterol and triglycerides  in blood depends on genetic factors, environment, and above all on dietary habits.  Therefore, in order to prevent hypercholesterlemia and arteriosclerosis it is best to decrease the quantity of cholesterol in meals by choosing  fats which derive from vegetables; decrease the share of saturated fatty acids, i.e. animal fats and increase the share of polyunsaturated fatty acids i.e. vegetable fats and especially oils

Symptoms of fat deficiencies