بسم الله الرحمن الرحيم
Community Medicine
Lec-4-Learning objectives
At the end of this lecture student would be able to : 1-Determine fats constituents . 2-Classify fatty acids . 3-Illustrate functions of dietary & body fats . 4-Outline health problems of fats . 5-Identify functions & properties of essential fatty acids . 6-Discuss cholesterol & types of lipoproteins . 7-Enumerate indications & contraindications of weight reduction . To a level accepted to the accreditation standard of the College .Fats are compounds of glycerol with fatty acids. Fatty acids are either saturated or unsaturated. By hydrogenation ,unsaturated fatty acids are changed into saturated ones. Hydrogenation destroy the essential fatty acids. Essential fatty acids can not be synthesized by human body.
Fats
Glycerol + one fatty acids Monoglyceride. Glycerol + 2 F.A. Diglyceride. Glycerol + 3 F.A. Triglyceride.Unsaturated fatty acids present mainly in vegetable oil and play an important role in having a lowered serum cholesterol level. Triglycerides are oily droplets circulate in blood shielded with water soluble proteins in the lipoprotein complexes.
Essential fatty acids are essential for maintaining normal health,otherwise its absence will create specific health problems e.g. linoleic acid , linolenic acid,and arachidonic acid deficiency states or conditions.
Occurrence of fats In general fats could be either of plant origin or of animal origin.
In plants,fats are formed from carbohydrates .The plant seeds when become ripen,starch content becomes less while fatty content increase.e.g. cotton seeds ,sun flower seed.Otherwise most vegetables and fruits contain a very little amount of fats.Plant origin fats are usually of unsaturated fatty acids.In animals,when much starchy food has been consumed fats are laid down in animal body.Some naturally formed fats contain vitamins such as vitamin A,D and E .Animal origin fats are usually of saturated fatty acids.Functions of dietary fats 1.Source of energy Fats are essential nutrients that supply a high energy density. 1 gram 9 Cal. 20% of daily required energy is ideally derived from fats. 2.Supply of essential fatty acids specially linoleic acid. 3.Supply of fat soluble vitamins. 4.Food satisfaction feeling Fats has a slow gastric emptying thus it play a satisfactory role against rapid hunger.
Functions of body fats
1.Energy production The major function of fats in the body is energy supplement to all body tissues except central nervous system. 2.Thermal insulation for body The fatty layer beneath the skin (subcutaneous fat) preserve the overall body temperature. 3.Vital organs protection The adipose tissues which surround vital organs in the body display a protective role for these organs against trauma .e.g.kidney.5.Tissue membranes structure Fats are vital constituents for tissues and cells membrane structure and help in the transport of nutrients and metabolites across membrane. 6.Cell metabolism The combination of protein with fats help in cell metabolism .Lipoproteins carry fats in blood to all cells.
The fatty layer which surround the nerve fibers provide electrical insulation and enhance the transmission of nerve impulses.
4.Nervous stimuli transmission
7.Precursor substances.Fatty acids and cholesterol are essential precursors for the synthesis of many materials that are needed by the body for maintaining metabolic functions and tissue integrity.
Health problems of fats A.Excess amounts of fat intake can lead to much adipose tissues deposition and thus overweight or obesity. B.Excess saturated fatty acids intake usually associated with a great risk to develop atherosclerosis or arteriosclerosis.
Essential fatty acids functions and properties 1. Strengthening function for capillary and cell membrane ( increase its permeability). 2.Combine with cholesterol and enhance its transport. 3.Help in lowering serum cholesterol levels. 4.prolongation of blood clotting time and increase the fibrinolytic activity. 5.It help in prostaglandins formation and functions on platelets smooth muscles.
Cholesterol
It is not a fatty material .It is a fat related substance. It traveled in blood stream attached to a long chain of fatty acids to form cholesterol esters. It is a vital substance in human metabolism. It is an important precursor for all steroid hormones. It is essential for bile acids formation. It is found naturally in all animal origin foods especially in egg yolk,liver and kidney.Otherwise,it can not be found in plant origin foods. Its main health related problems lie in cases of high serum cholesterol levels which reveal a direct association with atherosclerosis and I.H.D
1.Chylmicrons It is the lowest density i.e. small amount of proteins and high amount of triglyceride Liver cells. 2.Regular density lipoproteins (VLDL) tissue cells (endogenous triglycerides) 3. Intermediate low density lipoproteins (ILDL) endogenous triglycerides to cells.
lipoproteins
They serve as a major vehicle for transport of fats in blood stream.As fats are insoluble ,thus it trapped by water soluble proteins for transport. Types of lipoproteins are:-4.low density lipoproteins (LDL) Transfer cholesterol to peripheral tissues cells. 5.High density lipoproteins (HDL) Transfer free cholesterol to liver for catabolism and excretion.
Indications of weight reduction Although weight reduction is desirable measure for all obese persons to get rid of the somatic and psychological difficulties ,the followings are serious indications:- 1.Respiratory difficulties Excessive deposition of adipose tissue increase the work load of respiratory movements for keeping sufficient oxygenation of whole body tissues.
2.Hypertension Weight reduction can play an important role in the control of hypertension among obese persons.
3.Ischemic heart disease It is advisable to reduce weight during post coronary ischemia e.g. post angina or post infarction. 4.Endocrine and metabolic disturbances Uncontrolled diabetes, hirsutism and menstrual irregularities are more common among obese females. A better control of such disturbances can be obtained through weight reduction.
5.Reproduction difficulties Toxemia of pregnancy Infertility Serious reproductive difficulties can be eliminated through a proper weight reduction.
6.Gall stones and gall bladder diseases 7.Dermatological problems Skin rash,certain inflammatory skin conditions and varicose vein ulcers can be avoided through weight reduction. 8.Rheumatological problems. 9.Psychological indications.