Transcript DIGESTION and ABSORPTION

LIPIDS
Ch. 5
Triglycerides, Phospholipids,
and Sterols
LIPIDS
Learning Objectives:
•
Understand lipid terminology and
classifications
•
Understand digestion and absorption of
lipids
Understand transport of lipids in body
Learn about function of lipids in the diet,
and how they relate to health issues –
Heart Disease (Ch 18)
•
•
Heart Attack GrillMonument to Greasy Gluttony
https://www.youtube.com/watch?v=dDDbXh1MYc
Daily Consumption in the US
 47
million hotdogs
 2,250 cattle eaten as Big Mac’s
 13 pizzas the size of Roman Coliseum
 3 million gallons of ice cream
 6 million pounds of chocolate
WHAT ARE LIPIDS?
•
Organic compounds that contain carbon,
hydrogen, and oxygen
•
Hydrophobic – “water-fearing”
*Insoluble in water
•
Lipophilic – “fat loving”
•
Fats and Oils
p. 146
3 CLASSES of LIPIDS
Triglycerides
•
Made up of 3 Fatty Acids and Glycerol
• “Fats and Oils”
Phospholipids
•
Made of 2 Fatty Acids & phosphate bound to glycerol
• Emulsifiers
• Make up cell membranes
Sterols
•
Hydrocarbon ring structure
• Cholesterol, Bile acids, some hormones, Vit D
Building Blocks: FATTY ACIDS
 Key
building blocks for lipids/triglyceride
 Chains


of carbon atoms
Methyl group at one end (CH3)
Carboxyl group at the other (COOH)
CHEMISTRY OF FATTY ACIDS
 Influence
characteristics of fat in food &
health effects in our bodies


Solid or liquid @ room temp
Spoilage factors (oxidation)
 “Free”
3



or attached to another compound
Characteristics of Fatty Acids
Chain length
Degrees of saturation
Where first double bond is located
FATTY ACIDS
CHAIN LENGTH
*Naturally occurring FAs contain even
numbers of carbons
•
Short chain = less than 6 carbons
*Dairy Products
• Medium chain = 6-10 carbons
*Dairy Products, Tropical Oils
• Long chain = 12 or more carbons
*Most common in the diet
*Meat, fish, vegetable oils
FATTY ACIDS
2 Classifications:
•
SATURATED FATTY ACID =
Fully loaded with hydrogen atoms and
contains only single bonds between
its carbon atoms
FATTY ACIDS
2 Classifications:
•
UNSATURATED FATTY ACID =
Lacks hydrogen atoms and has at
least one double bond between
carbons
UNSATURATED FATTY ACIDS
2 Types:
•
Monounsaturated fatty acid (MUFA) =
Has one double bond
•
Polyunsaturated fatty acid (PUFA) =
Has two or more double bonds
Mono vs Poly Unsaturated
Unsaturated FA Food Sources
MUFA
PUFA
 Olive
 Vegetable
oil
 Canola oil
 Peanut oil
 Avocados





Safflower
Sesame
Soy
Corn
Sunflower
 Nuts
 Seeds
oils
Lipid Chemical Model Activity
Creating Fatty Acids
Face-to-face class:
* 6 groups
* Create an 8-carbon fatty acid
3 groups will make saturated FA’s
3 groups will make unsaturated FA’s
2 polyunsaturated FA’s, 1 monounsaturated FA
FATTY ACIDS Consistency
 Long-chain
saturated fatty acids stack
tightly


Solids at room temp
Animal fats
 Monounsaturated
& polyunsaturated fatty
acids don’t stack compactly…


Liquid at room temperature
Vegetable oils
 Short-chain
saturated fatty acids are also
liquid at room temperature
Characteristics of Fat at Room
Temperature
p134
UNSATURATED FATTY ACIDS
TWO TYPES OF BOND FORMATION:
•
CIS - hydrogens on carbons joined by
double bond are on same side = the
carbon chain is bent
•
TRANS – hydrogens on carbons joined by
double bond are on the opposite side =
the carbon chain is straighter
Comparing Cis and Trans
Trans Fatty Acids
•
HYDROGENATION: chemical process
where hydrogens are added to mono- or
polyunsaturated fats to reduce the number
of double bonds.
•
Results:


•
Fats are more saturated (solid)
Resistant to oxidation (rancidity).
Hydrogenation produces trans-fatty acids.
Process of Hydrogenation
 Take
a liquid oil through a process that
adds hydrogen and changes it to a solid
fat at room temperature
FATTY ACIDS
Essential Fatty Acids
 Body cannot make C-C double bonds
before the 9th carbon from the methyl
end


Omega-3
Omega-6
 Must

get them from our diet
Vegetable oils, seeds, nuts, fish, and other
marine foods
FATTY ACIDS
•
Omega-3:
ALA - Alpha-Linolenic Acid
EPA - Eicosapentaenoic Acid
DHA - Docosahexaenoic Acid
•
Omega-6:
Linoleic Acid
Arachidonic Acid
Sources of Omega-3
Fatty Acids
Linolenic Acid - ALA
EPA and DHA
 Flaxseed
 Fatty
oil
 Flaxseeds



 Soybean/Canola
Oil
 Chia/Hemp Seeds
 Walnuts
fish:
Salmon
Sardines
Mackerel
 Fish
oils
Sources of Omega-6
Fatty Acids
Linoleic Acid
Arachidonic Acid
 Seeds
 Meats
and nuts
 Vegetable oils




Corn
Safflower
Sunflower
Soybean
FATTY ACIDS
EICOSANOIDS
 Made
from arachidonic acid (Omega 6)
and EPA/DHA (Omega 3)

Hormone-like compounds - more localized
effect, different effects on different cells
 Important
in the…
Inflammatory process
Blood vessel dilation & constriction
Blood clotting
EICOSANOIDS
Omega-6s
 Linoleic acid -> arachidonic acid
-> eicosanoids formed
 Overall effect:



Constricting blood vessels
Promote inflammation
Blood clotting
EICOSANOIDS
Omega-3s
 Linolenic acid –> EPA and DHA ->
eicosanoids formed
 Overall effect
 Dilating blood vessels
 Discouraging blood clotting
 Reducing inflammation
 Support Heart Health
Table 5-H1 p162
3 CLASSES of LIPIDS
Triglycerides
•
Made up of 3 Fatty Acids and Glycerol
• “Fats and Oils”
Phospholipids
•
Made of 2 Fatty Acids & phosphate bound to glycerol
• Emulsifiers
• Make up cell membranes
Sterols
•
Hydrocarbon ring structure
• Cholesterol, Bile acids, some hormones, Vit D
TRIGLYCERIDES
STRUCTURE:
Triglyceride: 3 fatty acids + glycerol
Diglyceride: 2 fatty acids + glycerol
Monoglyceride: 1 fatty acid + glycerol
Condensation reactions – make triglycerides
Fatty Acids
Triglyceride
Condensation Reactions Form
Triglycerides
 Loss
of water
 Triglycerides
are the main form of fat
consumed in the _________ (95% as
fats and oils)
 Triglycerides
are the main form of fat
stored in the __________ (99%)
TRIGLYCERIDES
FUNCTIONS
 Stored
fat supplies much of energy
needs during rest – compactly
 Insulates
the body and keeps it warm
 Protects
bones & organs as a natural
shock absorber
 Sensory
qualities – flavor and texture
PHOSPHOLIPIDS
Glycerol bonded to 2 fatty acids & phosphate


Phosphate (hydrophilic) = dissolve in H2O
Fatty acids (lipophilic) = soluble in fat
 Ideal
emulsifier to mix or transport fats
in water
 Perfect
structure for cell membranes
PHOSPHOLIPIDS – Lecithin
Functions of Phospholipids
 Cell Membranes
 Major component of cell membranes
 Lipid Transport and Emulsifier
 In the stomach, intestine, bloodstream and
the lymphatic system
Phospholipids of a Cell Membrane
Figure 5-9 p136
Phospholipids as Emulsifiers
•
•
•
•
Combine foods that wouldn’t normally mix
Reduce fat separation (mayo)
Increase shelf-life
Prolong flavor release
Phospholipids in Foods
Lecithin (phosphatidylcholine)

Major phospholipid
Found in:





Liver
Eggs
Soybeans
Peanuts
Wheat germ
Liver produces
lecithin as well.
3 CLASSES of LIPIDS
Triglycerides
•
Made up of 3 Fatty Acids and Glycerol
• “Fats and Oils”
Phospholipids
•
Made of 2 Fatty Acids & phosphate bound to glycerol
• Emulsifiers
• Make up cell membranes
Sterols
•
Hydrocarbon ring structure
• Cholesterol, Bile acids, some hormones, Vit D
STEROLS
Hydrocarbons with a multiple ring
structure
•
Contain no fatty acids
•
Cholesterol is the best-known sterol,
found ONLY in animal food products
CHOLESTEROL: Functions
 Major
component of cell membranes
(abundant in nerve and brain tissue)
 Precursor
molecule:
Examples - Vitamin D, testosterone,
cortisol (adrenaline hormone)
 Important
in the synthesis of bile acids
CHOLESTEROL: Synthesis
 Liver
manufactures most of the cholesterol
in our bodies = 800 -1500 mg per day
 ~90%
of the body’s cholesterol is found in
the cells
Sterols in Plants

Similar in structure to cholesterol

Interfere with cholesterol absorption

Diets rich in plant sterols lower blood
cholesterol levels

Plant sterols & stanols are found naturally in
small amounts in:
•
•
•
•
•
Grains
Vegetables
Fruits
Legumes
Nuts & Seeds
LIPIDS
Learning Objectives:
•
Understand lipid terminology and
classifications
• Understand digestion & absorption of lipids
• Understand transport of lipids
• Learn about function of lipids in the diet,
and how they relate to health issues –
Heart Disease (Ch 18)
LIPID DIGESTION
Lipid Digestion
Mouth
 Chewing
mixes fats with saliva
 Some hard fats melt
 Lingual lipase found in saliva
 Minimal fat digestion here

Except in infants – lipase plays active role
Lipid Digestion
Stomach
 Muscular
actions mix fat with watery chyme
 Exposes
food to gastric lipase

Works in acidic conditions
 Little
digestion of fats occurs here
Lipid Digestion
Small Intestine
 Fat:
CCK → gallbladder → bile
Secretin → pancreatic juice →
pancreatic lipase
 Chyme:
 Villi:
Intestinal lipases
 Break
down TG’s to monoglycerides &
free FA’s
Importance of Bile…
Emulsified Fat & Enzymes
Digestion of Large Triglycerides
Form monoglyceride & 2 Free LCFA’s
LIPID DIGESTION
Mouth: chewing, lingual lipase
Stomach: strong muscular contractions, gastric lipase
Small Intestine: CCK → gallbladder → bile
Secretin → pancreatic juice → lipase
Micelles: tiny emulsified fat packets that can enter
intestinal cells (enterocytes)
Contain monoglycerides and LCFAs
Lipid Absorption
Small Intestine: duodenum or jejunum

Small lipid molecules

glycerol and short/medium chain fatty acids
DIFFUSE easily into enterocytes (intestinal cells)

Absorbed directly into blood stream
Lipid Absorption
Small Intestine: duodenum or jejunum
 Micelles



– emulsified fat packets
carry monoglycerides & long chain fatty acids to the
brush border
diffuse into enterocytes
Once in the enterocytes, monoglycerides and free
fatty acids are reformed into triglycerides
LIPID ABSORPTION
CHYLOMICRONS 
Transport lipids from intestine cells to rest of body
Consist of:
 Newly-formed
triglycerides
 Cholesterol
 Phospholipids
 Protein
carriers
Figure 5-16b p142
LIPID ABSORPTION
 Short-chain
fatty acids
 Medium-chain fatty acids
 Glycerol
→ Absorbed directly into bloodstream to liver
Chylomicrons enter the lymphatic system

Bypass liver, blood to body cells for immediate
use or storage
Lipid Absorption
Lipid Digestion/Absorption Review
LIPIDS
Learning Objectives:
•
Understand lipid terminology and
classifications
• Understand digestion & absorption of lipids
• Understand transport of lipids
• Learn about function of lipids in the diet,
and how they relate to health issues –
Heart Disease (Ch 18)
Transport of Lipids in the Body
Lipoproteins - combine lipids and proteins
 Chylomicrons
 Very
Low-Density Lipoprotein (VLDL)
 Low-Density
Lipoprotein (LDL)
 High-Density
Lipoprotein (HDL)
Lipoproteins in the Body
 Chylomicrons


Largest of lipoprotein
Transport dietary lipids (triglycerides
& cholesterol) from SI to rest of body
 Cells
remove TG’s
 Become
 Liver
chylomicron remnants
collects and recycles what’s left
Very Low Density Lipoprotein
VLDL
Lipids made in liver + chylomicron remnants
make -> VLDL
Shipped to rest of body
TG’s are removed by body’s cells
VLDL becomes smaller and more dense
→ LDL
Low-Density Lipoprotein
LDL
Contain mostly cholesterol
Distributes contents to cells:
new cell membranes
hormones
store for use later
LDL receptors on liver
Control amount of blood cholesterol by removing
LDL from circulation
High-Density Lipoprotein
HDL
 Made
by liver
 Removes
 Delivers
cholesterol from cells
it back to the liver for recycling or
disposal
 Has

anti-inflammatory properties
Prevents atherosclerotic plaques from
breaking apart & causing heart attacks
Size and Compositions of the Lipoproteins
Figure 5-16 p142
Lipoproteins in the Body
Lipid Transport Review
LIPIDS
Learning Objectives:
•
Understand lipid terminology and
classifications
• Understand digestion & absorption of lipids
• Understand transport of lipids
• Learn about function of lipids in the diet,
and how they relate to health issues –
Heart Disease (Ch 18)
Cholesterol in the Body
 “Good”


vs. “bad” cholesterol
↑ LDL - ↑ risk of heart attack
↑ HDL – protective against heart attacks
 Cholesterol
 Differences
is all the same
between LDL & HDL reflect
proportions & direction of movement of
cholesterol, not type
Dietary Cholesterol
 Overall
diet can affect the amount
absorbed


Dietary long chain saturated fat increases
cholesterol absorption
Fiber (especially soluble fiber) decrease
cholesterol absorption
Saturated Fats in the U.S. Diet
Milk, yogurt, and cheese 20%
Added fats and oils 34%
Other 2%
Eggs 2% Nuts and legumes 2%
Meat, poultry, and fish 40%
Fruits, grains, and vegetables are insignificant sources, unless
saturated fats are intentionally added to them during preparation.
Heart Disease
Nearly 1 million people die each year in the
United States related to CVD
Heart Disease (heart attack) = leading cause
of death in American men and women
Heart Disease
 Elevated




blood cholesterol
Saturated fat – may increase LDL?
Dietary choices – whole foods vs
American diet, low fiber
Trans-fats – increase LDL
decrease HDL
Dietary cholesterol?
Atherosclerosis
•
“Hardening and narrowing
of the arteries”
•
Accumulation of soft, fatty streaks along
inner arterial walls
•
•
Most people have well-developed plaques by
age 30
Slow, progressive disease - takes decades
to advance
Atherosclerosis
Plaque forms in response to injury along the artery
wall
Injury can be caused by:
High cholesterol
Hypertension
Smoking
Diabetes
Homocysteine
Diets high in saturated or trans fat
Infections
Progression of build-up….
Atherosclerosis Video
Artery Explorer:
http://www.youtube.com
/watch?v=GBf59Z8tgA0
What Are Risk Factors for CVD?
Potentially:


High LDL Cholesterol
Low HDL Cholesterol


But actually depends on the subtypes of these lipoproteins
An atherogenic diet:
High in…
 Highly processed foods
 Trans-fatty acids
 Too many refined carbohydrates
• Refined grains and sugar
Low in veggies, fruits, whole plant foods
Comparing Types of Fats in Meals
Animal fats (in moderation) are fine, focus on whole-plant food fats
• Minimally processed animal products are fine in the diet
when the diet is plant-based as a whole
• I do recommend consuming all of the foods in the righthand column regularly
Other CVD Risk Factors
Age & Gender
Men - age 45
Women - age 55
More women will die from heart disease
Family History
More members, earlier age of onset - ↑ risk
Other CVD Risk Factors
Smoking
More you smoke, ↑ risk
Damages heart, ↑ BP
Damages platelets – ↑ blood clots
Damages blood vessels, ↑ atherosclerosis
Diabetes
Blood vessels blocked, ↓ circulation
↑ infections, rapid atherosclerosis
↑ risk of death from CVD
Other CVD Risk Factors
Physical inactivity & Obesity…abdominal obesity
Contributes to ↑ LDL, ↓ HDL, HTN, diabetes
Exercising & weight loss – ↓ LDL, ↑ HDL, ↓ BP, improves
insulin sensitivity
Metabolic Syndrome
Includes 3 of 5 factors indicating metabolic disorders
1. abdominal obesity
2. ↑ TG’s
3. ↓ HDL
4. ↑ BP
5. ↑ fasting glucose
Associated with many chronic diseases
Overeating and physical inactivity contribute to this
Factors that Lower LDL and/or
Increase HDL
 Weight
 More
Control
mono & polyunsaturated fats
 Soluble
dietary fibers
 Phytochemicals
 Moderate
(whole-food plants)
alcohol consumption
 PHYSICAL
ACTIVITY
Trans Fats & Health Effects
Trans Fatty Acids

Raise total blood cholesterol

Raise LDL cholesterol
 Lower HDL cholesterol

FDA mandates grams trans fats included on the
Nutrition Facts panel (2006)
Food Sources: pages 148, 162
How to Detect Trans-fat
Other Dietary Considerations
Homocysteine – high levels may promote
atherosclerosis, excessive blood clotting, or
blood vessel rigidity
Omega-3 Fatty Acids – support heart health
Soluble Fiber – help lower cholesterol levels
Antioxidants – clean up free-radicals
(Vitamin E, Vitamin C, etc)
Coconut Oil
 Composed
mostly of MCTs (MCFAs)
 MCTs may help protect against heart disease
Other health benefits:






Kills bacteria, viruses, fungi, yeast, parasites
Improves digestion/absorption of vit/min
Reduces inflammation
Aids immune system function
May aid in weight loss
Keeps skin & hair healthier
Recommended Intakes of Fat
DRI and 2010 Dietary Guidelines recommend fat at
20-35% of energy intake
(400 - 700 calories of a 2,000-kcalorie diet)

FDA: 10% of energy intake from saturated fat
30% of energy intake total fat
Heart Healthy Eating with Fats
Reduce trans fats and other artificial fats
Reduce refined polyunsaturated vegetable oils
Soybean, canola, corn oils
Increase whole-food plant sources of fats
Nuts, seeds, avocados, olives, etc.
Consume healthy saturated fats
Coconut, macademia nut, grass-fed butter
Consume unrefined, extra virgin monounsaturated
oils (olive, avocado)
Focus on omega 3-rich foods