FATS

Lipids

• Triglycerides (fats and oils)

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• Phospholipids

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• Cholesterol

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Functions:

• Add flavor to food- fats carry flavor
• Satisfies hunger
• Fats take longer to digest than any other nutrient
• Supply calories for energy
• Fats contain the most concentrated form of energy, 9 calories per gram

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Functions (cont):

• Body fat helps maintain body temperature
• Helps protect body organs from bumps & bruising
• Fats carry the fat soluble vitamins A,D,E, & K

TYPES OF FAT:

• Saturated
• Monosaturated
• Polyunsaturated
• Trans fats
• Cholesterol

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Lipids in the Body

(Cholesterol)

• 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

Saturated Fat:

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• Molecules of fats that are saturated with hydrogen atoms
• Cause the level of LDL cholesterol in the blood to rise, but do not affect levels of HDL cholesterol
• Solid at room temperature

Food Sources:

• Usually of animal origin:
• Meats & poultry (especially the skin)
• Eggs
• Dairy products (milk & cheese)

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Monounsaturated Fat:

• Molecules of fat with one free carbon-hydrogen bond
• These fats lower LDL cholesterol levels in the blood, & raise the HDL cholesterol in the blood, therefore they are considered “healthy” fats

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• Monosaturated fats come from plant foods: olive oil & canola oil
• Monounsaturated fats are liquid at room temperature

Polyunsaturated Fat:

• Fat molecules with many free carbon-hydrogen bonds
• These fats lower LDL cholesterol levels in the blood, but do not affect the HDL cholesterol in the blood, therefore they are considered “healthy” fats, but not as good for you as monounsaturated

• Liquid at room temperature
• Come mostly from plant food: vegetable oils, avocados, nuts, seeds & many fish

Trans Fat:

• These are unsaturated fats that have been hydrogenized
• These fats raise LDL and lower HDL- they are the worst fats you can eat
• Commonly found in processed food, margarine, shortening

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• Hydrogenation: process of adding hydrogen to oils. This process causes the oil to become solid, but it also turns an unsaturated fat into a saturated fat

Fatty Acids Are Key Building Blocks

• Chain length
• 4 to 24 carbons

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

• Essential and nonessential fatty acids
• Essential fatty acids
• Can’t be made in the body
• Linoleic acid and alpha-linolenic acid
• Used to make eicosanoids “local hormones”

Fatty Acids Are Key Building Blocks

• Essential and nonessential fatty acids
• Nonessential fatty acids
• Can be made in the body

Triglycerides

• Structure
• Glycerol + three fatty acids
• Functions
• Energy source
• 9 kcal/g
• Form of stored energy in adipose tissue
• Insulation and protection
• 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
• Sources of omega-6 fatty acids
• Vegetable oils

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Photos © PhotoDisc

Phospholipids

• Structure
• Glycerol + two fatty acids + phosphate group
• Functions
• 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
• Sterol hormones
• Vitamin D
• Bile acids
• Synthesis
• Made in the liver
• Food sources
• Found only in animal foods

Lipid Digestion and Absorption

• 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 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

Photos © PhotoDisc

Lipids in the Diet

• Fat replacers
• Different types of composition
• Olestra
• Sucrose + fatty acids
• Indigestible—provides no calories
• Reduces absorption of fat-soluble 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

• Reducing heart disease risk
• Lifestyle
• Stop smoking
• Increase exercise
• Manage weight
• Manage blood pressure

Lipids and Health

• Reducing heart disease risk
• Diet
• Reduce saturated fat, cholesterol, total fat
• Increase antioxidants
• Increase B vitamins
• Increase omega-3 fatty acids
• Increase dietary fiber
• Other factors

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

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Lipids and Health

• Cancer
• Stages of development
• Initiation
• Promotion
• Progression
• Role of diet
• Factors that promote or protect

Lipids and Health

• Cancer
• Reducing cancer risk
• Eat a variety of healthful foods; plant sources
• Be more physically active
• Maintain a healthful weight
• Limit alcohol consumption