‫بسم هللا الرحمن الرحيم‬
Community Medicine
Lecture-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 .
Fats
Fats are compounds of glycerol with fatty acids.
Glycerol + one fatty acids
Glycerol + 2 F.A.
Glycerol + 3 F.A.
Monoglyceride.
Diglyceride.
Triglyceride.
 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.
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.
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.
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.
4.Nervous stimuli transmission
The fatty layer which surround the nerve fibers provide
electrical insulation and enhance the transmission of
nerve impulses.
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.
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
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
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: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.
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.
Contra-indications of weight reductions
1.Tuberculosis.
2.Gout.
3.Diverticulitis.
4.Adisons disease.
5.Ulcerative colitis.
Thank You All