Transcript The Lipids: Triglycerides, Phospholipids, and Sterols

The Lipids:
Triglycerides,
Phospholipids, and
Sterols
Chapter 5
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Introduction
 Poor health
 Too much fat
 Too little fat
 Too much of some kinds of fat
 Family of lipids
 Triglycerides
 Phospholipids
 Sterols
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
 Energy provided per gram
 More carbons and hydrogens
 Preview of lipids
 Triglycerides: glycerol and 3 fatty acids
 Fatty acids: even number of carbons
 Fatty acids: saturated or unsaturated
 Omega-3 and omega-6 fatty acids
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
 Fatty acids
 Organic acid
 Methyl group at one end; acid group at other
end
 Usually even number of carbons
 18-carbon fatty acids abundant in food
 Saturations
 Saturated – full of hydrogens
 Unsaturated – missing hydrogens
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
 Fatty acids
 Location of double bonds
 Nearest the methyl end of the carbon chain
 Omega number
 Linolenic acid
 Monounsaturated fatty acids
 Omega-9 groups
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
 Triglycerides
 Glycerol backbone
 Three fatty acids
 Formed via series of condensation reactions
 Usually contain mixture of fatty acids
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
 Degree of unsaturation
 Firmness
 Polyunsaturated fats
 Saturated fats
 Length of carbon chain
 Stability
 Oxidation and spoilage of fats
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
 Degree of unsaturation
 Hydrogenation
 Advantages
 Trans-fatty acids
 Configurations – cis and trans
 Similarity to other types of fat
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of Fatty Acids
and Triglycerides
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of
Phospholipids and Sterols
 Phospholipids
 Solubility in fat and water
 Emulsifiers in food industry
 Lecithin
 Food sources
 Roles
 Part of cell membranes
 Emulsifiers
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Chemist’s View of
Phospholipids and Sterols
 Sterols
 Food sources
 Cholesterol
 Plant sterols
 Roles of sterols
 Body compounds made from cholesterol
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Digestion
 Fats are hydrophobic
 Digestive enzymes are hydrophilic
 Goal of fat digestion
 Dismantle triglycerides
 Monoglycerides, fatty acids, and glycerol
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Digestion
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Digestion
 Mouth
 Lingual lipase
 Stomach
 Strong muscle contractions
 Gastric lipase
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Digestion
 Small intestine
 Cholecystokinin (CCK)
 Gall bladder releases bile
 Bile acts as emulsifier
 Pancreatic lipase
 Hydrolysis
 Triglycerides and phospholipids
 Bile routes
 Blood cholesterol levels
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Emulsification of Fat by Bile
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Fat
Watery GI
juices
Enzymes
In the stomach,
the fat and
watery GI juices
tend to separate.
The enzymes in
the GI juices
can’t get at the
fat.
Enzyme
Fat
Bile
Emulsified
fat
When fat enters
the small intestine,
the gallbladder
secretes bile. Bile
has an affinity for
both fat and water,
so it can bring the
fat into the water.
Emulsified
fat
Bile’s emulsifying
action converts
large fat globules
into small droplets
that repel each
other.
Emulsified
fat
After
emulsification,
more fat is
exposed to the
enzymes, making
fat digestion more
efficient.
Stepped Art
Fig. 5-14, p. 143
Hydrolysis of a Triglyceride
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Enterohepatic Circulation of
Bile
Whitney & Rolfes – Understanding Nutrition, 12th Edition
In the gallbladder,
bile is stored.
In the liver,
bile is
made from
cholesterol.
In the small intestine,
bile emulsifies fats.
In the colon, bile that has
been trapped by soluble
fibers is lost in feces.
Stepped Art
Fig. 5-16, p. 144
Lipid Absorption
 Directly into bloodstream
 Glycerol and short- & medium-chain fatty
acids
 Lymphatic system
 Micelles diffuse into intestinal cells
 Reassembly of triglycerides
 Packed with proteins – chylomicrons
 Bypass liver at first
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Absorption of Fat
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Transport
 Four main types of lipoproteins
 Chylomicrons
 Largest and least dense
 Transport diet-derived lipids
 Liver removes remnants from blood
 Very-low-density lipoproteins (VLDL)
 Made in the liver
 Proportion of lipid shift
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Transport
 Four main types of lipoproteins
 Low-density lipoproteins (LDL)
 Cell needs
 Liver regulation
 High-density lipoproteins (HDL)
 Remove cholesterol from cells
 Carry cholesterol to liver for recycling
 Anti-inflammatory properties
 Health implications
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Lipid Transport
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Role of Triglycerides
 Provide the cells with energy
 9 kcalories per gram
 Virtually unlimited ability to store fat energy
in body
 Adipose tissue
 Secretes hormones
 Adipokines
 Skin insulation, shock absorption, cell
membranes, and cell signaling pathways
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Essential Fatty Acids
 Linoleic acid – Omega-6 fatty acid
 Sources
 Linolenic acid – Omega-3 fatty acid
 Sources
 DHA
 EPA
 Eicosanoids
 Fatty acid deficiencies
Whitney & Rolfes – Understanding Nutrition, 12th Edition
A Preview of Lipid
Metabolism
 Adipose cells store fat after meals
 Lipoprotein lipase
 Hydrolyzes triglycerides
 Triglycerides reassembled inside adipose
cells
 Using fat for energy
 Protein sparing
 Energy deprivation
 Fasting and ketone bodies
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Health Effects of Lipids
 Heart disease
 Elevated blood cholesterol
 Saturated fat – increase LDL cholesterol,
promote blood clotting
 Dietary choices
 Trans-fats – increase LDL cholesterol
 Dietary cholesterol
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Health Effects of Lipids
 Heart disease
 Monounsaturated fats
 Replace saturated and trans fats
 Reduces blood cholesterol
 Dietary sources
 Omega-3 fats
 Benefits
 Dietary sources
 Omega-6 to omega-3 ratio
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Health Effects of Lipids
 Cancer
 Promotion rather than initiation of cancer
 Dietary fat and cancer risk
 Differs for various types of cancer
 Obesity
 Cutting fat from diet reduces kcalories
 Dietary recommendations
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Recommended Intakes of Fat
 DRI and Dietary Guidelines
 Diet low in saturated and trans fat
 Diet low in cholesterol
 20 to 35 percent of daily energy from fat
 AI set for linoleic and linolenic acids
 Daily Values (DV) on food labels
 Saturated fat and cholesterol
 Risk of insufficient fat intake
Whitney & Rolfes – Understanding Nutrition, 12th Edition
From Guidelines to Groceries
 Fat-soluble vitamins
 A, D, E, and K
 Flavor, texture, and palatability
 Meats and meat alternatives
 Selections
 Milk and milk products
 Selections
Whitney & Rolfes – Understanding Nutrition, 12th Edition
From Guidelines to Groceries
 Vegetables, fruits, and grains
 Lowers consumption of various fats in the
diet
 Invisible fat
 Fried and baked goods
 Choose wisely
 Unprocessed foods
Whitney & Rolfes – Understanding Nutrition, 12th Edition
From Guidelines to Groceries
 Fat replacers
 Types
 Risks
 Read food labels
 Total fat, saturated fat, trans fat, and
cholesterol
 Compare products
 % Daily Value vs. % kcalories from fat
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Butter and Margarine Labels
Compared
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Highlight 5
High-Fat Foods – Friend or Foe?
Whitney & Rolfes – Understanding Nutrition, 12th Edition
Guidelines for Fat Intake
 Limit saturated fat and trans fat intake
 Moderate kcalories
 Enough fat for good health
 Not too much of the harmful fats
 DRI recommendations
 Compatible with low rates of disease
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Health
 Olive oil
 Benefits for heart health
 Replace saturated fats
 Nuts
 LDL cholesterol
 Fat composition
 Benefits for heart health
 Cautious advice for dietary inclusion
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Health
 Fish
 Omega-3 fatty acids
 Benefits for heart health
 Environmental contaminants
 Dietary recommendations
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Health
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Disease
 Saturated fat and LDL cholesterol
 Sources of saturated fat in the U.S.
 Meats
 Whole milk products
 Tropical oils
 Zero saturated fat is not possible
 Trans fat
 Limit hydrogenated foods
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Disease
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Disease
Whitney & Rolfes – Understanding Nutrition, 12th Edition
High-Fat Foods and Heart
Disease
Whitney & Rolfes – Understanding Nutrition, 12th Edition
The Mediterranean Diet
 Traditionally
 Low in saturated fat
 Very low in trans fat
 Rich in unsaturated fat
 Rich in complex carbohydrate and fiber
 Rich in nutrients and phytochemicals
 Benefits for heart disease risk
Whitney & Rolfes – Understanding Nutrition, 12th Edition