Lipids are called fats when they are at room temperature, or oils when they are in a liquid state. They are molecules composed of O, H and C, insoluble in water. They are classified into three types: triglycerides, phospholipids, cholesterol and their derivatives.
Types of lipids
Triglycerides: this type of lipids make up 95% of the diet, made up of a glycerol skeleton and three fatty acids. They constitute the lipid reserve in adipose tissue (adipocytes). The short and medium chain are digested in the mouth and stomach, and the long chain in the small intestine.
Phospholipids: formed by a glycerol skeleton, one or two fatty acids, a phosphate group and a charge head that varies according to the type of phospholipid. They are synthesized through triglycerides. Lecithin is the most abundant phospholipid and can be found in egg yolks, liver, and peanuts. They are the main components of the cell membrane.
Cholesterol: this lipid is formed in the liver, although it is not self-sufficient and must be ingested through the diet, with a maximum of 300mg / day. Only 35% -40% of ingested cholesterol is absorbed. It does not provide kcal and is only found in animal products. It is a precursor of bile salts, necessary for the digestion of fats, and a multitude of hormones (testosterone, cortisol, vit. D). There is a correlation of high LDL levels with cardiovascular diseases and problems, due to blockage of blood vessels.
Fat deposits in animals and humans are found in the subcutaneous tissue and the abdominal cavity. Fat is used as a vehicle for the intake of fat-soluble vitamins (A, E, D K).
Lipids are concentrated in: red meat, oils, inexpensive products, dairy products. The functions of lipids are energy function (9 kcal / g), structural function (biological membranes) and regulation of metabolism (steroid hormones). Their absorption is slower than that of hydrates and they require chylomicrons for transport. Its energy is obtained through the triglycerides found in adipose tissue, which releases glycerol and fatty acids. Glycerol is incorporated in glycolysis and fatty acids in beta oxidation
During the absorption of lipids, short and medium chain triglycerides are digested in the mouth and stomach, and long chain ones in the small intestine.
There are several types of lipoproteins
Types of lipids according to their lipoproteins
VDL: transports fat from the liver to the rest of the body
IDL: provide triglycerides to the muscle as the main source of energy
LDL: main carrier of cholesterol that is deposited in cells
HDL: transports excess cholesterol from liver cells to eliminate it
Fatty acids can be: saturated, unsaturated
Saturated: are related to cardiovascular problems, they should not exceed 10% kcal per day. They present greater stability to oxidation, they are cholestorogenic (they increase cholesterol in the blood). They are in the solid state when they exceed 30% of the mixture. They undergo the transformation of unsaturated fatty acids (liquid) to saturated (solid) through hydrogenation, this produces fatty acids that are shared as saturated. We can find them in margarine, bacon, butter, pastries.
Unsaturated: omega 3,6,9 fatty acid supplement . They have improvements in the cardiovascular system, facilitate the supply of oxygen to the tissues and thereby improve oxygen levels during exercise.