Fat usually means any ester of fatty acids or mixture of such compounds most commonly those that occur in living beings or in food. Fat is used as the fatty components of foods and diet. Fats are best known members of a chemical group called the lipids. Content  Classification  Functions  Sources  Digestion  Absorption  Deficiency and disorders of lipids  Essential fatty acid  Role of omega-3 & omega 6 fatty acids in physiological disorders  References

1. Submitted by-
KOMAL OJHA
PhD student
Department of Food Science and Nutrition
CCAS, MPUAT, Udaipur

2. Content
 Classification
 Functions
 Sources
 Digestion
 Absorption
 Deficiency and disorders of lipids
 Essential fatty acid
 Role of omega-3 & omega 6 fatty acids in
physiological disorders
 References

3. Introduction
 Fat usually means any ester of fatty acids or mixture of such
compounds most commonly those that occur in living beings
or in food.
 Fat is used as the fatty components of foods and diet.
 Fats are best known members of a chemical group called the
lipids.
 The term lipid is applied to a group of naturally occurring
substances characterized by their insolubility in water, greasy
feel and solubility in organic solvent like ether, chloroform,
benzene or other fat solvents.
 The term lipid was first used by the German biochemist Bloor
in 1943.

4. Composition
• Lipids like carbohydrates are composed of the 3
elements carbon, hydrogen and oxygen.
• The lower amount of O in relation to the other two
elements results in lipids being a more concentrated
source of energy than carbohydrate.
• Eg,-
1gm of C - 4 kcal
1gm of P - 4 kcal
1gm of F - 9 kcal

5. Chemical Composition
• Triglycerides- Triglycerides or Triacylglycerols
are the main form of fat both in foodstuffs and
in the storage depots of most animals. The are
esters of glyerols and fatty acids (1:3).

6. •Fatty acids
Fatty acids are carboxylic acids with hydrocarbon side chain. The are the
simplest form of lipids. Over 40 different fatty acids are found in nature.
Fatty acids are classified based on length of carbon chains into 3 groups
short chain with less than 8 carbons; medium chain with 10-14 carbons and
long chain with 16-24 carbons.

7. Classification
• Lipids are classified as simple, compound and derived lipids
based on composition.
1. Simple lipids- esters of fatty acids with certain alcohols.
They are usually further classified acc. to the nature of the
alcohols.
eg. Fats and oils, waxes
2. Compounds or complex lipids- ester of fatty acids which on
hydrolysis yield other substances in addition to fatty acids
and an alcohol.
3. Derived lipids – These are substances liberated during
hydrolysis of simple and compound lipids which still retain
the properties of lipids.

8. Compound lipids
•Phospholipids: Phospholipids are a major component of the lipid bilayer of
the cell membrane and are found in many parts of the body.
•Sphingolipids: Sphingolipids are mostly found in the cell membrane of
neural tissue.
•Glycolipids: The main role of glycolipids is to maintain lipid bilayer
stability and facilitate cell recognition.
•Glycerophospholipids: Neural tissue (including the brain) contains high
amounts of glycerophospholipids.
•Cholesterols: Cholesterols are the main precursors for different hormones in
our body such as progesterone and testosterone. The main function of
cholesterol is controlling the cell membrane fluidity.
• Steroid – see also steroidogenesis: Steroids are one of the important cell
signalling molecules.

9. • Eicosanoids: Eicosanoids are made from fatty acids in the
body and they are used for cell signaling.
• Ketone bodies: Ketone bodies are made from fatty acids in the
liver. Their function is to produce energy during periods of
starvation or low food intake.
• Lipoproteins: These compounds found in mammalian plasma
are composed of lipid material bound to proteins. The lipids
mostly consists of cholesterol esters and phospholipids
containing principally stearic, palmitic and oleic acids
although palmitoleic, linoleic and arachidonic acids have been
identified.

11. Functions
Fat
Protector
Essential
constituent of
the membrane
of every cell
Regulator of
body
function
Absorption of
fat soluble
vitamins
Insulator
Source of
energy
Energy
reserve

12. 1. Essential constituent of the membrane of every cell-
fat is present not only in the outer membranes of cells but also in the internal
membranes of the nucleus, endoplasmic reticulum and the other membranes
bound organelles.
2. Energy reserve:
fat is the primary form in which energy is stored in the body. 1 pound (454g)
of stored fat represent 3500kcal of stored energy. Some fat can be stored
within most cells but the body also contain large numbers of specialised
cells, adipocytes, within adipose tissue.
3. Absorption of fat soluble vitamins:
fat soluble vitamins like A,D,E,K are absorbed in the body through fat.
4. Regulator of body functions: As an essential components of all cell
membranes, fat indirectly help to regulate both the flow of material into and
out of the cell and change in cell size and shape such as those involved in
growth.

13. I. Specific long chain omega-6 and omega-3 unsaturated fatty acid
also act as the precursors of a range of hormone like substances,
the eicosanoids, involved in the regulation of a wide variety of
the processes in the body.
II. Eicosanoids include the classes of important physiological
regulators known as prostaglandins, thromboxanes,
leukotrienes.
III. Eicosanoids perform many functions, including the regulation
of blood pressure, the control of important aspects of the
reproductive cycle, the stimulation of pain and fever and the
induction of blood clotting.
5. Insulators:
Deposits of fat beneath the skin known as the subcutaneous fat,
serves as an insulating material for the body and is effective at
preventing heat loss.

14. Sources
• Nuts and oil seeds are excellent sources of fat. The visible fats
are butter, ghee and oil.
• Invisible fats are present in cereals, pulses, oil seed, milk and
egg.
• Fruits and vegetables are poor source of fat.
Table 01: fat content of foods
Name of food stuff Fat g/100g
Ghee & oil 100
Butter 81
Coconut dry 62
Cashew nut 40
Groundnut 25
Cheese 23
Egg (Hen) 13

15. Digestion and
Absorption

16. Lipid digestion begins in the mouth, continues in the stomach, and ends in
the small intestine.
1. Mouth
• The digestion of fat is initiated by the lingual lipase enzymes. This
enzymes mixes with chewed food and hydrolyses fatty acid from
triglycerides to form diglycerides as the food travels down the oesophagus
to the stomach.
•It has an optimum pH of 2.5-5
• Lingual lipase hydrolyses short chain and medium chain triglycerides
more readily than it does long chain triglycerides.
2. Stomach (gastric lipase)
• Gastric lipase is acid stable with an optimum pH around 5.4
• It is secreted by chief cells, the secretion is stimulated by gastrin.
• The food mass passes into small intestine, where the presence of fat
stimulates the release of the hormones cholecystokinin and secritin.
•

17. • These hormones, in turn, stimulates the secretion of pancreatic
juice from pancreas and release bile which is synthesised in liver.
• Upto 30% digestion of triglycerides occurs in stomach.
3. Small intestine ( Emulsification of lipids)
• Emulsification is a prerequisite for digestion of lipids
• The lipids are dispersed into smaller droplets; surface tension is
reduced and surface area of droplets is increased.
 This process is favoured by:
1. Bile salts ( detergent action)
2. Peristalsis (mechanical mixing)
3. Phospholipids ( surfactants)

18. 1. Bile salts:
• Bile salts are the biological detergents synthesized from cholesterol in the liver.
• They are secreted with bile into the duodenum
• Bile salts are the most effective biological emulsifying agents
• They interact with lipid particles and the aqueous duodenal contents and convert
them into smaller particles (emulsified droplets)
• The bile salts lower surface tension
• The emulsification increases the surface area of the particles for enhanced activity
of enzymes

19. 2 . Phospholipids ( surfactants)
• The initial digestive products of lipids (catalysed by lipase).
Free fatty acids, monoacylglycerols promote emulsification
• These compounds along with phospholipids are known as
surfactants
• Surfactants get absorbed the water-lipids interface and
increase the interfacial area of lipid droplets
• Mechanical mixing due to peristalsis also help in the
emulsification

20. Absorption
• Glycerol, short and medium chain fatty acids(chain length less
than 14 carbon) are directly absorbed from the intestinal lumen
in to the portal vein and taken to live for further utilization.
• Long chain fatty acids, free cholesterol and β-acyl glycerol
together with bile salts form mixed micelles

21. Micelles
 Micelles are disk shaped cluster of
amphipathic lipids that coalesce with
their hydrophobic groups on the inside
and their hydrophilic groups on the
outside of clusters.
 Mixed micelles are soluble in the
aqueous environment of the intestinal
lumen.
 The micelles approach the brush
membrane of the enterocytes.

22. • Micelles constantly break down and re-form
• It is monoglycerides and fatty acids that are free in
solution that are absorbed, not the micelles.
• Because of their nonpolar nature, monoglycerides and
fatty acids can just diffuse across the plasma
membrane of the enterocytes.
• Some absorption may be facilitated by specific
transport proteins.

23. Transport
• Due to the hydrophobic nature of membrane lipids, triglycerides
and cholesterols, they require special transport proteins known as
lipoproteins.
• The amphipathic structure of lipoproteins allows the triglycerols
and cholesterol to be transported through the blood.
• Chylomicrons are one sub-group of lipoproteins which carry the
digested lipids from small intestine to the rest of the body.
• The varying densities between the types of lipoproteins are
characteristic to what type of fats they transport. For example, very-
low-density lipoproteins (VLDL) carry the synthesized triglycerides
by our body and low-density lipoproteins (LDL) transport
cholesterol to our peripheral tissues.
• A number of these lipoproteins are synthesized in the liver, but not
all of them originate from this organ.

24. Metabolism
• Short chain fatty acids enter the circulation directly but most
of the fatty acids are reesterified with glycerol in the intestines
to form triglycerides that enter into the blood as lipoprotein
particles called chylomicrons.
• Lipoprotein lipase acts on these chylomicrons to form fatty
acids. These may be stored as fat in adipose tissue, used for
energy in any tissue with mitochondria using oxygen and
reesterified to triglycerides in the liver and exported as
lipoproteins called VLDL (very low density lipoproteins).
• VLDL has a similar outcome as chylomicrons and eventually
is converted to LDL (low density lipoproteins). Insulin
simulates lipoprotein lipase.
• During starvation for long periods of time the fatty acids can
also be converted to ketone bodies in the liver. These ketone
bodies can be used as an energy source by most cells that have
mitochondria.

25. Degradation
• Fatty acids are broken down by Beta oxidation. This
occurs in the mitochondria and/or in peroxisomes to
generate acetyl-CoA. The process is the reverse of
fatty acid synthesis: two-carbon fragments are
removed from the carboxyl end of the acid. This
occurs after dehydrogenation, hydration, and
oxidation to form a beta-keto acid.
• The acetyl-CoA then converts to ATP, CO2, and H2O
using the citric acid cycle and releases energy of 106
ATP.

26. Deficiency and Disorders of lipids
1. Skin Problem
• When essential fatty acids are
missing from our diet it can cause
skin problems.
• An essential fatty acid deficiency
increase the loss of water from your
skin, which results in dry, scaly rash.
• This type of deficiency can also
make it harder for your wound to
heal.

27. Phrynoderma
• Hair emerge from the roots through the same follicles. In
follicular hyperkeratosis, the follicles become blocked with
plugs of keratin derived from their epithelial lining which has
undergoes squamous metaplasia.
• Because of the roughness in appearance, the condition has been
called Toad skin or Phrynoderma.
• Phrynoderma can be cured by EFA along with vitamins A and
B- complex group.

28. 2. Cognitive Problem
• Eicosapentaenoic acid (EPA) and
Docosahexaenoic acid (DHA) are
essential for brain.
• Not having enough DHA may
result in learning deficits and
increase the risk for certain types
of dementia.

29. 3. Vision Problems
• EPA and DHA are also
important components of
the retina.
• DHA helps from the
pigment rhodopsin, which
need for your brain to turn
the light hitting your retina
into the image you see.

30. Effects of excess fat in Human
1. OBESITY
• Taking in more calories than you can expend in an
average day makes you gain weight, placing strain
on your cardiovascular, respiratory and other body
systems.

31. 2. Constipation
• Diets that are high in fat can
affect your digestive organ.
• If a diet is high in saturated fat to
the detriment of your fiber
intake, you may become
constipated frequently.

32. 3. ATHEROSCLEROSIS
• Consuming a lot of
saturated fat affects your
blood cholesterol and
arterial health.
• Atherosclerosis thickening
or hardening of the arteries.
It is caused by a buildup of
plaque in the inner lining of
an artery.

33. Fatty acids
• Fatty acids are carboxylic
acids with hydrocarbon side
chain. The are the simplest
form of lipids. Over 40
different fatty acids are
found in nature.
• Fatty acids are classified
based on length of carbon
chains into 3 groups short
chain with less than 8
carbons; medium chain with
10-14 carbons and long
chain with 16-24 carbons.
fig.- shows the natural fatty acids and their
occurrence

34. Saturated fatty acid
• Saturated fatty acids have no double bonds in the chain or contain single
chain.
• Their general formula is CH3(CH2)nCOOH, where n specifies the number
of methylene groups between the methyl and carboxyl carbons.
• They have higher melting points
• They are solid at room temperature
• Eg. lauric, myristic, palmitic acid etc.

35. Fatty acids
( saturated FA)
C atoms and double bonds Occurrence
1. Short chain
• butyric acid
•Caproic acid
•Caprylic acid
C4 : 0
C5 : 0
C6 : 0
Butter
Butter, coconut oil
Butter, coconut oil
2. Medium chain
• capric acid
• lauric acid
•Myristic acid
C10 : 0
C12: 0
C14 : 0
Butter, coconut oil
Butter, coconut oil
Butter, coconut oil
3. Long chain
• Palmitic acid
• Stearic acid
• Arachidic acid
C16 : 0
C18: 0
C20 : 0
Most veg. and animal fats
”, cocoa butter, fully
hydrogenated vegetable oil
Butter, lard, peanuts oil
Table : the important natural fatty acids and their occurrence

36. Unsaturated fatty acid
• These fatty acid contain one or more double bonds along
the length of the hydrocarbon chain.
• They are liquid at room temperature
• Have low melting point
• Eg., linoleic acid, oleic acid, palmitoleic acid

37. Table : the important natural fatty acids and their occurrence
Fatty acids
( unsaturated FA)
C atoms and double
bonds
Occurrence
1. Monounsaturated FA
• Palmitoleic acid
• oleic acid
C16 : 1
C18 : 1
Olive oil, fish, beef fat
Olive oil, nuts, seeds,
avocado
2. Polyunsaturated FA
• Linoleic acid
• α- linolenic acid
•Arachidonic acid
• Eicosapentaenoic acid
• Docosahexaenoic acid
C18 : 2(n-6)
C18 : 3(n-3)
C20 : 4(n-6)
C20 : 5(n-3)
C22 : 6(n-3)
Veg. seed oils (corn,
soyabean, cotton seed)
” walnuts, flax seeds
Fats & animal tissues ( liver,
lard, meat, poultry, fish,
eggs)
Fish oils, shell fish, algae
Fish oils, shell fish, algae

39. Omega-6 and omega-3 fatty acids are polyunsaturated fatty acids (PUFA),
meaning they contain more than one cis double bond. In all omega-6 (ω6 or
n-6) fatty acids, the first double bond is located between the sixth and
seventh carbon atom from the methyl end of the fatty acid. Likewise, all
omega-3 fatty acids (ω3 or n-3) have at least one double bond between the
third and fourth carbon atom counting from the methyl end of the fatty
acid.
1. Prevent cancer-
ω-3 fatty acids have been found to prevent cancer of breast and colon in
human by inhibiting tumour cell growth.
2. Anti-inflammatory effect:
ω-3 fatty acids foods increase the cell membrane content of both EPA and
DHA which increase the production of ant-inflammatory group icosanoid.

40. 3. Formation of prostaglandins:
It is responsible for the formation of prostaglandins found in every
single cell of the body. Prostaglandins regulate cell activities including
transmission of genetic information from generation to generation.
4. Defense mechanism:
It creates healthy cell walls and supports the defense mechanism of the
body as well as detoxification activity. It makes cell membrane more
permeable. The permeability of the membrane help in protecting the
cell against invading bacteria, toxins, infections and viruses. The cell
membrane also facilitates the flow of nutrients and waste materials in
and out of the cell.
5. Role in extracellular matrix:
It regulates the activity of the extra cellular matrix, which do not only
supports the cells in the various organs but also influences
multiplication, development, movement, shape and biochemical
functions of the cells.

41. Omega-6 fatty acids are polyunsaturated fatty acids that perform
essential functions in the human body. The most abundant
member of this family in food and in the body is linoleic acid.
Other members include gamma-linolenic acid and arachidonic
acid. Linoleic acid is considered an essential fatty acid since it
cannot be synthesized by the body. However, other members of
the omega-6 family can be made from linoleic acid.

42. Omega-6 fatty acids have numerous important roles in the body.
• They contribute to the structure and function of cell
membranes and play a part in the regulation of gene activity
inside the cell.
• Arachidonic acid is especially abundant in the brain, and may
be important for normal brain development of the fetus and
infant.
• Both arachidonic acid and gamma-linolenic acid can be
converted to prostaglandins and related substances that affect
inflammation, blood clotting, smooth muscle tone, and many
other body activities.

44. References
1. Siri-Tarino, P.W., et al., Saturated fatty acids and risk of coronary heart disease:
modulation by replacement nutrients. Curr Atheroscler Rep, 2010. 12(6): p. 384-90.
2. Hu, F.B., Are refined carbohydrates worse than saturated fat? Am J Clin Nutr, 2010.
91(6): p. 1541-2.
3. Jakobsen, M.U., et al., Intake of carbohydrates compared with intake of saturated
fatty acids and risk of myocardial infarction: importance of the glycemic index. Am
J Clin Nutr, 2010. 91(6): p. 1764-8.
4. Hu, F.B., et al., Dietary fat intake and the risk of coronary heart disease in women. N
Engl J Med, 1997. 337(21): p. 1491-9.
5. Ascherio, A., et al., Dietary fat and risk of coronary heart disease in men: cohort
follow up study in the United States. BMJ, 1996. 313(7049): p. 84-90.
6. Hu, F.B., J.E. Manson, and W.C. Willett, Types of dietary fat and risk of coronary
heart disease: a critical review. J Am Coll Nutr, 2001. 20(1): p. 5-19.

45. 7. Fiske ST, Dupree C. Gaining trust as well as respect in communicating to motivated audiences
about science topics. Proc Natl Acad Sci U S A. 2014;111(Suppl 4):13593–13597.
doi: 10.1073/pnas.1317505111.
8. Brownell SE, Price JV, Steinman L. Science communication to the general public: why we need
to teach undergraduate and graduate students this skill as part of their formal scientific
training. J Undergrad Neurosci Educ. 2013;12(1):E6–E10.
9. Gallop P. Americans Still Avoid Fat More than Carbs. Gallop Press; 2014.
10. US Department of Health and Human Services; US Department of Agriculture. Health.gov,
1985 Dietary Guidelines for Americans. Washington, DC: US Dept of Health and Human
Services; 1985.
11. Austin GL, Ogden LG, Hill JO. Trends in carbohydrate, fat, and protein intakes and
association with energy intake in normal-weight, overweight, and obese individuals: 1971-
2006. Am J Clin Nutr. 2011;93(4):836–843. doi: 10.3945/ajcn.110.000141.
12. Ogden CL, et al. Prevalence of childhood and adult obesity in the United States, 2011-
2012. JAMA. 2014;311(8):806–814. doi: 10.1001/jama.2014.732.
13. Mozaffarian D, Ludwig DS. Dietary guidelines in the 21st century--a time for
food. JAMA. 2010;304(6):681–682. doi: 10.1001/jama.2010.1116.
14. Heidemann C, et al. Dietary patterns and risk of mortality from cardiovascular disease, cancer,
and all causes in a prospective cohort of women. Circulation. 2008;118(3):230–237.
doi: 10.1161/CIRCULATIONAHA.108.771881.
15. Diekman C, Malcolm K. Consumer perception and insights on fats and fatty acids: knowledge
on the quality of diet fat. Ann Nutr Metab. 2009;54(Suppl 1):25–32. doi: 10.1159/000220824.