This document discusses lipids and fats. It defines fats and classifies them as simple, compound, or derived lipids. Fats can also be classified by their fatty acid composition as saturated, monounsaturated, or polyunsaturated. The document outlines the daily recommended intake of fats and their main sources. It describes the digestion, absorption, metabolism and functions of fats, as well as deficiencies from too little or too much fat. Cholesterol is also discussed.

1. Unit 3rd nutrition

2. Objective
• Define fats
• Classification of fat
• Daily recommend dose
• Sources
• Function
• Digestion, absorption and storage
• Metabolism
• Deficiencies of fats
• Over consumption

3. LIPIDS
• Fats and oils belong to a group of compounds called lipids.
They are characterized by greasy feel, insolubility in water
and solubility in some organic solvent.
• Like the carbohydrates, they are mainly made up of
carbon, hydrogen and oxygen.
• They are more concentrated source of energy providing
two and half times more energy than carbohydrates and
proteins.
• Unlike carbohydrates lipids contain of oxygen and a larger
proportion of hydrogen and carbon.
• Fats are solid at 20°C. They are called oils if they are liquid
at that temperature.

4. Cont…
• Simple fats and oils are of great importance in
food preparation.
• The quality of the food product depends
largely on the fats and oils used for while
preparing it.
• The most common form of food fats are
triglyceride.

5. CLASSIFICATION OF LIPIDS
• A. On the Basis of Structure:-
• 1. Simple lipids.
• 2. Compound lipids.
• 3. Derived lipids.
• 4. Sterol.

6. Cont…
• Simple lipids:- They are made up of three fatty
acids attached to glycerol. They are mixed
triglycerides which means that more than one
type of fatty acids are present in the fat, e.g.
cooking oils and butter. Simple lipids constitute
more than 98% of food and body fats.
• Compound lipids:- They are fats in which at least
one fatty acid is replaced by carbohydrate,
protein or phosphorus i.e. they are fats + non fat
molecules, e.g. phospholipids, glycolipids and
lipoprotein.

7. Cont…
• Derived lipids- They are the breakdown
products of fats and include diglycerides,
mono-glycerides, glycerol and fatty acids.
• Sterol:- They are not made up of fatty acids
and glycerol but have benzene ring structure.
These fat like substances include cholesterol
and fat soluble vitamins A, D, E and K

8. B. Classification of lipids on the basis
of fatty acids present
• 1. Saturated fatty acids
• 2. Unsaturated fatty acids :
• -Mono unsaturated fatty acids
• -Poly-unsaturated fatty acids
• 1. Saturated fatty acids :- In saturated fatty acids, each carbon atom
in the fatty acid carries all the hydrogen atoms possible.
• They have single bonds between carbon atoms.
• Saturated fatty acids are found mainly in animal fats and plants too
for example, coconut and palm oils although vegetable oils have an
extremely high percentage of saturated fatty acids and they are
solid.

9. Cont…
• 2. Unsaturated fatty acids:- The full
complement of hydrogen atoms is not
received in unsaturated fatty acids. This leads
to the formation of double bond between the
atoms so they have one or more double bonds
between the carbon atoms. Unsaturated fatty
acids are further divided into two-
• 1) Mono unsaturated fatty acids (MUFA)
• 2) Poly unsaturated fatty acids (PUFA)

10. Cont…
• 1) Mono unsaturated fatty acids (MUFA):- They
have one or more double bonds between the
carbon atoms. Oleic acid is an example of
monosaturate fatty acid and it is found in ground
nut oil, olive oil and corn oil. They are mostly
found in vegetable oils. There is exception as, for
example, fish oils contain mono and
polyunsaturated fatty acids and it is liquid.
• 2) Poly unsaturated fatty acids :- Fatty acids with
two or more double bounds. Examples are
linoleic, linolenic and arachidonic.

11. Cont…
• Cholesterol:- It is fat like substance present in food. It is different in
structure from triglycerides. It is present in all cells of the body,
large amount in brain and nerve tissue. Large amount of cholesterol
is also present in sebum secreted by the sebaceous glands. The
blood of normal human being contains 150-200 mg / 100 ml blood.
The human body gets cholesterol from two sources, one it is
synthesized in the liver.
• It performs following functions :-
• 1) Cholesterol is a boding of all steroid hormones.
• 2) It is also a bond of vitamin D.
• 3) It is required for formation of bile.
• 4) It is an essential constituent of cell membranes.
• If it is consumed in excess, it leads to diseases of the
cardiovascular system .

12. Cont…
• Visible and invisible fats:- Visible fats are those
which are separated from their natural sources,
e.g., ghee from milk, cooking oils from seeds and
nuts. So it is easy to estimate their intake in daily
diet.
• Invisible fats are those which are not visible to
naked eyes. They are present in almost every
article of food, e.g. cereals, pulses, nuts, milk,
eggs, etc. It is difficult to estimate their intake. In
fact the major contribution to total intake is from
invisible sources.

13. Functions of fats :-
• 1) Energy - Fats are a concentrated source of energy. One gram of
fat gives 9 kcal when it is oxidized in the body. All tissues except
those of central nervous system and brain can utilize fat as a source
of energy. Fats are deposited in the adipose tissue and this deposit
serves as a reserve source of energy during starvation.
• 2) Thermal insulation- Subcutaneous fat acts as an insulator
against cold by retaining body heat.
• 3) Protein sparing action:- An adequate intake of fat in the diet
allows proteins to perform their main functions of growth and
maintenance. In this way, fats spare proteins from being oxidized
for energy.
• 4) Protection of vital organs :- Fat provides a protective padding to
vital organs, Such as heart, kidney and intestine from mechanical
shock and keeps them in place.

14. Cont…
• 5) Absorption of fat soluble vitamins- Fats are
essential for the absorption of fat soluble vitamins A, D,
E and K, especially carotenoids present in foods of
vegetable origin. So fats serve as vehicles for fat
soluble vitamins.
• 6 ) Essential fatty acids: Fats contain essential fatty
acids, viz. linoleic, linolenic and arachidonic acids,
which are essential for maintaining tissues in normal
health.
• 7) Satiety value- Fats improve the
palatability(svaadisht) of the diet and give satiety
value, i.e., a feeling of fullness in the stomach.

15. Cont…
• 8) Synthesis of hormones:- The cholesterol is
necessary for the synthesis o- some steroid
hormones and bile acids, e.g., sex hormone.
• 9) Precursors of prostaglandins:- Poly
unsaturated fatty acids are precursors of
prostaglandins - a group of compounds now
recognised as "local hormones." They play a
major role in controlling many of the
physiological functions.

16. Sources of Fats
• Animal fats: The major sources of animal fats are ghee,
butter, milk, cheese, egg, yolk, meat and fish. Animal
fats are mostly saturated fats.
• Vegetable fats: Some plants store fat in their seeds,
e.g. groundnut, mustard soybeans, sesame(tiil),
coconut, almond(badam), cashew nut(kaju), safflower
and sunflower etc.
• Other sources-Small quantities of fat (invisible) are
found in most other foods such as cereals, pulses and
vegetables. Large cereal consumption in India provides
considerable amounts of invisible fats.

18. Fat Requirement
• The WHO expert committee on prevention of Coronary
Heart Disease (CHD) has recommended 20 to 30
percent of total dietary energy to be provided by the
fats.
• At least 50 percent of fat intake should consist of
vegetable oils rich in essential fatty acids.
• The Indian Council of Medical Research
(ICMR) 1989 has recommended a daily intake of not more
than 20 percent of total energy intake through fats.
• In developed countries dietary fats provide 30 to 40
percent of total energy.

19. Digestion and Absorption of Fats
• When a person takes his food it enters the
stomach where gastric lipase produces slight
hydrolysis of fat (process of splitting into smaller
molecules by uniting with water).
• In the duodenum, bile secretion emulsifies fats.
Pancreatic lipase and intestinal lipase break down
the fats into a mixture of monoglyceride,
diglycerides and fatty acids. The products of
digestion pass through the lacteals of the small
intestines to the thoracic duct, then to the blood
stream and every cell of the body.

20. Fat Metabolism
• The liver assists in the oxidation of fats and prepares
fats for deposition in the tissues. In the tissues, some
of the fat is oxidized to give heat and energy. Some of
the fat is stored in the fat deposits. Fats, before they
can be used as body fuel, must be prepared for
combustion in the tissues by the liver. This is a chemical
process carried out by the liver cell is known as the
desaturation of fats.
• The waste products which result from the combustion
of fat in the carbon dioxide and water, excreted by the
lungs, skin and kidneys.

21. Cont..
• If the combustion is incomplete, the acetone
bodies are formed and also leave the body by the
same routes.
• The volatile acetone can be smelt in the "sweet
breath" and acetone and diacetic acid can be
found in the urine.
• Fat is a better fuel than glucose, in that it
produces twice as much heat and energy per
gram of fuel used. On the other hand, it is less
easy to digest, absorb and less satisfactory to
burn provided it is burnt with sufficient sugar.

22. Cont…
• If there is little or no sugar to burn with it,
combustion is incomplete and ketone bodies
are formed. When large amount of ketone
bodies are formed, this condition is known as
acidosis, which results in drowsiness, coma
and finally death.
• Fat, which is not used as fuel, can be stored as
fatty tissues and in the body cavities. It can be
stored in large quantity causing obesity.

23. Effects of Deficiency
• A deficiency of fat may result in a deficiency of
fat soluble vitamins which may affect the
growth and weight of the children.
• Deficiency of essential fatty acids in the diet
leads to a condition known as phrenoderma
or toad skin.

25. Effects of Excessive Fats
• The greater concern today is the problems related to
excessive intake of fats. It can pose a threat to human
health. Excessive fat causes obesity as it is stored in the
adipose tissues. In normal subjects, adipose tissues
constitute between 10 to 15 percent of body weight
but in fat people it may increase to 30 percent. Most of
the body fat is in the form of triglycerides.
• Hypercholesterolemia and Coronary Heart Disease
When the blood cholesterol level is over 250 mg per
100 ml, the incidence of atherosclerosis and Coronary
heart disease is high

27. Question to be Ask ?
• Define fat and classify it ?
• Source and function of fat
• Deficiency and over use ?
• Short note on cholesterol ?
• Source of fat ?