Transcript Lipids - Napa Valley College

Lipids: Not Just Fat
Chapter 6
Lipids
• Essential nutrients
• Provide energy
• Help transport fatsoluble nutrients
• Contribute to flavor
and texture of food
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Lipids
• What are lipids?
– Triglycerides
• Stored in adipose tissue
• Fats and oils in food
– Phospholipids
• Plant and animal origin
• Body can make them
• Soluble
– Sterols
• Cholesterol
Fatty Acids Are Key Building Blocks
• Fatty acid
– Determines solid or liquid
• Chain length
– 4 to 24 carbon length
Fatty Acids Are Key Building Blocks
• Saturation
– Saturated fatty acid
• All single bonds between carbons
– Monounsaturated fatty acid
• One carbon–carbon double bond
– Polyunsaturated fatty acid
• More than one carbon–carbon double bond
Fatty Acids Are Key Building Blocks
• Cis vs. trans
– Cis fatty acids
• Occur naturally
• Chain is bent
– Trans fatty acids
• Produced by
hydrogenation
• Chain is
straighter
Fatty Acids Are Key Building Blocks
• Nonessential and essential fatty acids
– Nonessential fatty acids
• Can be made in the body
• Not “essential” to have in your diet
Fatty Acids Are Key Building Blocks
• Nonessential and
essential fatty acids
– Essential fatty acids
• Can’t be made in the
body
• Must come from food
• Linoleic acid and
alpha-linolenic acid
• Used to make
eicosanoids
Triglycerides
• Structure
– Glycerol + three fatty acids
• Functions
– Energy source
• 9 kcal/g
– Energy reserve
• Form of stored energy in adipose tissue
– Insulation and protection
• Visceral fat
– Carrier of fat-soluble vitamins
– Sensory qualities in food
Triglycerides
• Functions
– Insulation and protection
• Visceral fat
– Carrier of fat-soluble vitamins
– Sensory qualities in food
Triglycerides in Food
• Sources of omega-3 fatty acids
– Soybean, canola, walnut, flaxseed oils
– Salmon, tuna, mackerel, fish-oil
supplements
• Sources of omega-6 fatty acids
– Seeds, nuts, vegetable oils
– Meat, poultry, eggs
• Commercial processing
– Oxidation
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Phospholipids
• Structure
– Glycerol + two fatty acids +
phosphate group
• Phospholipid functions
– Keeps fat suspended in water
– Component of cell membranes
– Lipid transport as part of
lipoproteins
– Emulsifiers
• Food sources
– Egg yolks, liver, soybeans,
peanuts
Sterols: Cholesterol
• Functions
– Component of cell membranes
– Precursor to other substances
• Vitamin D
• Sterol hormones
• Bile salts
• Synthesis
– Made in the liver
• Sterols in food
– Found only in animal foods
Lipid Digestion and Absorption
• Digestion of triglycerides and phospholipids
– Mouth and stomach
• Minimal digestion of triglycerides
– Small intestine
• Emulsified by phospholipids
• Digested by pancreatic lipase
• Absorbed into intestinal cells
–Formed into chylomicrons and moved
into lymphatic system
Lipids in the Body
• Lipid absorption
– Micelles
– Lipoproteins carry
lipids around the
body
– Chylomicrons
• Deliver dietary
lipids from
intestines to cells
and liver
Lipids in the Body
• Digestion and absorption of sterols
– About 50% of dietary cholesterol is
absorbed
• Dietary fat increases absorption
• Dietary fiber decreases absorption
Lipids in the Body
• Very-low-density lipoproteins (VLDL)
– Deliver triglycerides to cells
• Low-density lipoproteins (LDL)
– Deliver cholesterol to cells
• High-density lipoproteins (HDL)
– Pick up cholesterol for removal or
recycling
Lipids in the Diet
• Recommended intake
– Reduce saturated and trans fat
intake
– Total fat: 20–35% of calories
– Need approximately 2% of
kilocalories as essential fatty
acids
– Improve balance of
omega-3 and omega-6 fatty
acids
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Lipids in the Diet
• Fat replacers
– Different types of
composition
– Olestra
• Sucrose + fatty
acids
• Indigestible—
provides no
calories
• Reduces
absorption of fatsoluble vitamins
Lipids and Health
• Obesity
– High-fat diets promote weight gain
• Heart disease
– Major risk factors
• High blood cholesterol
–High LDL and low HDL
• Smoking
• High blood pressure
Lipids and Health
• Atherosclerosis
– Slow hardening and narrowing of arteries
– Promoted by high blood cholesterol
– Lipoprotein a [Lp(a)]
– C-reactive protein
Lipids and Health
• Reducing heart disease risk
– AHA diet and lifestyle recommendations
• Consume an overall healthy diet
• Aim for a healthy body weight
• Aim for a desirable lipid profile
• Aim for normal blood pressure
• Aim for normal blood glucose levels
• Avoid use of and exposure to tobacco
products
Lipids and Health
• Reduce heart disease risk
– AHA recommendations plus other risk factors
• Balance calorie intake and physical activity
to achieve or maintain a healthy body weight
• Consume a diet rich in fruits and vegetables
• Choose whole-grain, high-fiber foods
• Consume fish at least twice a week
• Limit your intake of saturated and trans fat
and cholesterol
Lipids and Health
• Reduce heart disease risk
– AHA diet and lifestyle recommendations
• Minimize your intake of beverages and
foods with added sugars
• Choose and prepare foods with little of
no salt
• If you consume alcohol, do so in
moderation
• Follow the AHA recommendations when
eating outside of the home
Lipids and Health
• Metabolic syndrome
– Cluster of at least three symptoms
• Excess abdominal fat
• High blood glucose
• High serum triglycerides
• Low HDL cholesterol
• High blood pressure
Lipids and Health
• Putting it all together
– Healthy People 2010 objectives target
reducing deaths from heart disease and
stroke and reducing the number of adults
with high blood cholesterol levels
Lipids and Health
• Cancer
– Stages of development
• Initiation
• Promotion
• Progression
– Role of diet
• Factors that promote or protect
Lipids and Health
• Cancer
– Nutrition and physical activity guidelines for
cancer prevention
• Maintain a healthful weight
• Adopt a physically active lifestyle
• Consume a healthy diet
• If you drink alcohol, limit consumption