Title: Chapter 5 The Lipids:
1Chapter 5The Lipids
- Triglycerides
- Phospholipids
- Sterols
2Objectives for Chapter 5
- Discuss synthesis, structures, classification,
function and metabolism of lipids - Identify the dietary sources of the different
types of lipids - Discuss the role of lipoprotein in transport of
lipids - Describe the relationship of lipids to chronic
diseases - List current dietary recommendations for lipids
and how to implement them.
3Lipids
- Lipids are a class of nutrients that includes
- Triglycerides (fats and oils)
- Phospholipids
- Sterols.
- Composed of carbon, hydrogen, and oxygen.
- Lipids are hydrophobic (insoluble in water)
- Include fat soluble vitamins (ADEK)
- Provides 9 kcal per gram
4Triglycerides
- TG (fats and oils) composed of 3 fatty acids
attached to a glycerol - Fatty acid - is a chain of carbon atoms with
hydrogen attached that has an acid group (COOH)
at one end and a methyl group (CH3) at the other
end - Glycerol is an alcohol composed of a three carbon
chain
5 Methyl end
Acid end
Fig. 5-1, p. 140
6TG
7Triglycerides
- Fats are lipids that are solid at room
temperature (70 degrees) - Oils are lipids that are liquid at room
temperature (70 degrees) - TGs are 95 of dietary fats
- Roles of TGs
- Energy reserve when stored
- Insulation
- Shock protection
- Use carbohydrate and protein efficiently
8Fatty Acids
- Fatty acids Fatty acids vary in carbon chain
lengths, degree of unsaturation, and number of
double bonds. - Length of the carbon chain
- Long-chain fatty acids are found primarily in
meat, fish, and vegetable oils. - Medium- and short-chain fatty acids are found in
dairy products. - Degree of Saturation- Saturation affects the
physical characteristics of the fat and its
storage properties - Saturated fatty acids carry the maximum possible
number of hydrogen atoms.
9Saturated vs. Unsaturated
- Saturated - When most of the fatty acids are
saturated it is called a saturated fat.
Stearic acid, an 18-carbon saturated fatty acid
10Saturated vs. Unsaturated
- Unsaturated Unsaturated fatty acids are missing
at least 2 hydrogen atoms and have at least one
double bond. There are 2 types - Monounsaturated fatty acid (MUFA)
Oleic acid, an 18-carbon monounsaturated fatty
acid
11Saturated vs. Unsaturated
- Polyunsaturated fatty acids (PUFA)
- lack four or more hydrogen atoms and have at
least two or more double bonds. - Linoleic and linolenic acid - Essential Fatty
Acids (EFAs) - When most of the fatty acids in a lipid are
polyunsaturated it is called a polyunsaturated
fat.
Linoleic acid, an 18-carbon polyunsaturated fatty
acid
12Saturated vs. Unsaturated
- Locations of the double bonds
- Omega3 - linolenic acid - the first double bond
is located at the third carbon from the methyl
side - Omega 6 - linoleic acid - the first double bond
is located at the sixth carbon from the methyl
side
Linoleic acid, an 18-carbon polyunsaturated fatty
acid
13Omega-3 and Omega-6 Fatty Acids Compared
14Saturated and Unsaturated Fatty Acids Help Shape
Foods
15Fatty Acids
- Degree of unsaturation
- Firmness
- Saturated fats - solid at room temperature.
Mostly from animal sources - Polyunsaturated fats - liquid at room
temperature. Found in vegetable oil except, cocoa
butter, palm oil, palm kernel oil, and coconut
oil - Stability
- Saturated fat is more resistant to oxidation.
- Monounsaturated fat is less susceptible to
spoilage. - Polyunsaturated fat spoils most readily.
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17Essential Fatty Acids
- Essential Fatty Acids
- Linoleic Acid - Omega-6 Family and 18 carbon
- They are PUFA,
- Can make arachidonic acida conditionally
essential fatty acid with 20 carbons and 4 double
bonds - Supplied by vegetable oils and meats
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19Essential Fatty Acids
- Linolenic Acid and 18 Omega-3 Family
- EPA - eicosapentaenoic acid, 20 carbon, 5 double
bonds - DHA - docosahexaenoic acid, 22 carbons and 6
double bonds - important for eyes, brain development, and heart
disease. - Eicosanoids omega 3 6
- Made from arachidonic acid and EPA
- Like hormones but have different effects on
different cells - Include prostaglandins, thromboxanes, and
leukotrienes - Essential fatty acid deficiencies are rare in the
US but my occur in children fed low fat or fat
free diet
20Essential Fatty Acids
21Fatty Acids
- Hydrogenation
- Hydrogen atoms are added to monounsaturated or
polyunsaturated fats - Act more like saturated fats
- resistant to oxidation
- Prolong shelf life
- Becomes solid at room temperature
- Trans-Fatty Acids vs. Cis
- Naturally, most double bonds are cis, hydrogen
next to the double bonds are on the same side. - Trans, hydrogens on opposite side of the carbon.
- Trans fatty acids behave like saturated fat in
the body.
22Cis- and Trans-Fatty Acids Compared
23Major Food Sources of Trans Fat for American
Adults
24Phospholipids
- Phospholipids
- contain glycerol, 2 FAs and a phosphate group
with a choline. - A well-known phospholipid is lecithin, made by
the liver - Food sources of lecithin include eggs, liver,
soybeans, wheat germ and peanuts. - Soluble in both water and fat
- Roles of phospholipids
- Transport lipids and FSV through Plasma membrane
- Used as emulsifiers in food industry
25Phospholipids
26Sterols
- Sterols
- cholesterol, vit D, testorone
- Multiple-ring structure.
- Found in plant and animal foods
- Cholesterol is found in animal foods only - meat,
eggs, fish, poultry and dairy products
27Sterols
28Sterols
- Roles of sterols
- Needed to make bile acids, sex hormones, adrenal
hormones and vitamin D - Component of cell membranes
- Liver produces 800-1500mg of cholesterol daily
- Cholesterol forms deposits in the artery wall
causing artherosclerosis.
29Fat Digestion
- Mouth
- hard fat begin to melt as they reach body
temperature - salivary glands - lingual lipase digests short
and medium chain fatty acids found in milk. - Stomach
- Lingual lipase breaks down triglycerides to
produce diglycerides and fatty acids - gastric lipase breaks down a small amount of fat.
- Little fat digestion takes place in the stomach.
30Fat Digestion
- Small Intestine
- most of the digestion takes place in the small
intestine. - Cholecystokinin (CCK) signals gallbladder to
release bile. - Pancreatic and intestinal enzymes breaks lipids
to monoglycerides and fatty acids. - Phospholipids are broken down as well.
- Sterols are absorbed intact as is.
- Bile is reabsorbed in the small intestine
- Colon or large intestine
- Soluble fibers traps some bile and excreting it
from the body through the large intestine.
31Lipid Absorption
- Lipid Absorption
- Glycerol and short and medium-chain fatty acids
diffuse and are absorbed directly into the
bloodstream. - Monoglycerides and long-chain fatty acids form
micelles, are absorbed, and are reformed into new
triglycerides. - With protein they are transported by chylomicrons
32 Monoglyceride
Micelle
Protein
Triglyceride
Long-chain fatty acids
Chylomicron
Large lipids such as monoglycerides and
long-chain fatty acids combine with bile, forming
micelles that are sufficiently water soluble to
penetrate the watery solution that bathes the
absorptive cells. There the lipid contents of the
micelles diffuse into the cells.
33Lipid Transport
- Lipid transport is made possible by a group of
vehicles known as lipoproteins. There 4
lipoproteins - Chylomicrons
- Largest of the lipoproteins
- Least dense
- Get smaller as triglyceride portion is removed by
the cells - VLDL (Very-Low-Density Lipoproteins)
- Composed primarily of triglycerides
- Made by the liver
- Transport lipids to the tissues
- Get smaller and more dense as triglyceride
portion is removed
34Lipid Transport
- 3. LDL (Low-Density Lipoproteins)
- Composed primarily of cholesterol
- Transport lipids to the tissues
- 4. HDL (High-Density Lipoproteins)
- Composed primarily of protein
- Transport cholesterol from the cells to the liver
35Chylomicrons One Type of Lipoprotein
36The Various Types of Lipoproteins and Their
Composition
37Lipid Transport
- Health Implications
- High LDL is associated with higher risk of heart
attack and is known as bad cholesterol. - High HDL seems to have a protective effect and is
known as good cholesterol
38Storing Fat
- Storing Fat as Fat
- Adipose tissue readily stores fat.
- Provides twice the energy as carbohydrate and
protein - 1 lb of body fat 3,500 cal
- Lipoprotein lipase (LPL) breaks triglycerides as
they pass, directs the parts into the cells to be
used for energy or storage. - Using Fat for Energy
- Fat supplies 60 of the bodys ongoing energy
needs. - lipase inside the adipose cells hydrolyzes
triglycerides when needed for energy. - Fasting metabolizes fat but needs carbohydrate
and protein for complete breakdown. - Ketone bodies
39Health Effects of Lipids
- Normal blood lipid profile
- Total cholesterol ? 200 mg/dL
- LDL cholesterol ? 100 mg/dL
- HDL cholesterol ? 60 mg/dL
- Triglycerides ? 150 mg/dL
- Atherosclerosis - Cholesterol accumulates in the
arteries - saturated fats raise LDL
- Trans fat increase LDL cholesterol and decrease
HDL cholesterol - Cholesterol has less effect on blood cholesterol
than saturated fat and trans fat.
40Atherosclerosis
41Health Effects of Lipids
- Increasing dietary MUFA PUFA is the most
effective way to prevent heart disease. - omega-3 fats help to reduce risk of heart disease
and stroke - Balance omega-6 and omega-3 intakes
- Cancer - Fat does not initiate cancer development
but may be a promoter once cancer has developed - Obesity- consequence of high fat diet
42Recommended Intakes of Fat
- DRI and the 2005 Dietary Guidelines recommends
fat at 20-35 of energy intake. - FDA - 10 of energy intake from saturated, 30 of
energy intake total fat - 2005 Dietary Guidelines - choose a diet low in
saturated fat and cholesterol and moderate in
total fat.
43Recommended Intakes of Fats
- Recommended Intakes of Fat
- Daily Values
- 65 g fat based on 30 of 2000-kcal diet
- 20 g saturated fat based on 10 of 2000-kcal diet
- 300 mg cholesterol
- USDA Food Guide considers saturated fats
discretionary kcalories. - Too little fat can be detrimental to health.
44Recommended Intakes of Fat
- Linoleic acid AI
- 5 - 10 of energy intake
- Linolenic acid AI
- 0.6 - 1.2 of energy intake
45Reducing Fat In Your Diet
- Cook with olive oil
- Nibble on nuts
- Feast on fatty fish, high in omega 3
- But beware of mercury
- Limit Fatty Meats, Milk Products, and Tropical
Oils - Limit hydrogenated foods
46Reducing Fat in Your Diet
- Fat replacers
- Artificial, ingredients derived from
carbohydrate, protein or fat. - Replace fat in foods, but no added kcalories
- Olestra is safe but it deceases absorption of
fat-soluble vitamins and may cause diarrhea. - Limit Fatty Meats, Milk Products, and Tropical
Oils - Limit Hydrogenated Foods
- Adopt the Mediterranean diet
- Focus on whole grains, potatoes, and pasta,
vegetables and legumes, low fat cheeses, yogurt,
fruits, fish and seafood, poultry, a few eggs
and little meat
47Homework
- Extra credit 5 points
- Go to the supermarket and compile a list of 10
foods that contain hydrogenated fat in the
ingredient list and document the amount of trans
fat listed on the nutrition fact panel