Lipids Essential nutrients Provide energy Help transport fat- soluble nutrients Contribute to flavor...
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Lipids
• Essential nutrients• Provide energy• Help transport fat-
soluble nutrients• Contribute to flavor
and texture of food
Photo © PhotoDisc
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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 in fat and water
– Sterols• Cholesterol
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Fatty Acids Are Key Building Blocks• Fatty acid
– Determines solid or liquid at room temp– Basic structure: (-COOH); (-CH3)
• Chain length– 4 to 24 carbon length
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Fatty Acids Are Key Building Blocks• Saturation
– Saturated fatty acid• All single bonds
– Unsaturated fatty acid• One or more double bond
– Monounsaturated fatty acid• One double bond
– Polyunsaturated fatty acid• More than one double
bond
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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
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Fatty Acids Are Key Building Blocks
• Nonessential and essential fatty acids– Nonessential fatty acids
• Can be made in the body
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Fatty Acids Are Key Building Blocks
• Nonessential and essential fatty acids– Essential fatty acids
• Can’t be made in body• Must come from food• Omega-3 (alpha-linolenic
acid) and omega-6 (linoleic acid)
• Used to make eicosanoids
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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
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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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A healthy diet contains a balance of omega-3 and omega-6 fatty acids. Omega-3 help reduce inflammation.
Some omega-6 tend to promote inflammation.
The typical American diet contains 14 - 25 times more omega-6 than omega-3.
The ratio should be in the range of 2:1 - 4:1, omega-6 to omega-3.
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Phospholipids
– Glycerol + two fatty acids + phosphate group
• Phospholipid functions– Emulsifiers
• Keeps fat suspended in water• Keep oil and water mixed
– Cell membranes
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Phospholipids
• Cell membrane– Double layer of
phospholipids– Important role in
nerve cells
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Phospholipids
• Lipid transport– Stomach
• Break fats into tiny particles for digestion
– Intestine• Continue emulsifying fat
– Blood• Surface of lipoproteins that carry lipid particles
in the body
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Phospholipids• Emulsifiers (lecithin)
– In body• Phospholipid with
choline– In food
• Used as emulsifiers
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Sterols• Cholesterol functions
– In cell membranes– Precursor:
• Vitamin D• Sterol hormones• Bile salts
• Cholesterol synthesis in liver– Found only in animal foods
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Lipid Digestion and Absorption
– Mouth• Chewing + lingual lipase
– Stomach• Triglycerides to diglycerides and free fatty
acids (FFA)– Small intestine
• Emulsified by Bile• Digested by pancreatic lipase
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• Lipid absorption– Micelles
• Carry monoglycerides and fatty acids to microvilli
• Bile salts absorbed = enterohepatic circulation
• Lipoprotein• Cylomicron
–Deliver dietary lipids from intestines to cells and liver
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• Digestion and absorption of sterols– 50% of dietary cholesterol is absorbed
• Fat increases absorption• Plant sterols and dietary fiber decrease
absorption
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Lipids in the Body
– Very-low-density lipoproteins (VLDL)• Deliver triglycerides to cells
– Intermediate-density lipoproteins• Converted to LDL
– Low-density lipoproteins (LDL)• Deliver cholesterol
– High-density lipoproteins (HDL)• Pick up cholesterol for removal
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Lipids in the Diet
• Recommended intake– Reduce saturated fat, trans fat,
and cholesterol– Total fat: 20–35% of calories– Less than 10% of calories from
saturated fat– Less than 300 mg per day of
cholesterol
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Lipids in the Diet
• Role of fat replacers– Olestra
• Sucrose + fatty acids
• Indigestible— provides no calories
• Reduces absorption of fat-soluble vitamins
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Lipids and Health
• Obesity– High-fat diets promote wt gain
• Heart disease– Major risk factors
• High blood cholesterol–High LDL and low HDL
• Smoking• High blood pressure
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Lipids and Health
• Atherosclerosis– Slow, progressive hardening and narrowing
of arteries– Promoted by high blood cholesterol – Lipoprotein a [Lp(a)]
• Inflammation and atherosclerosis– C-reactive protein
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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• Be physically active• Avoid use of and exposure to tobacco
products
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Lipids and Health
• Reduce heart disease risk– AHA recommendations
• 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, especially oily fish, at least
twice a week• Limit your intake of saturated and trans fat
and cholesterol
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Lipids and Health
• Cancer– Stages of development
• Initiation• Promotion• Progression
– Role of nutrition and diet• Factors that promote or protect
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Lipids and Health
• Cancer– Dietary and lifestyle factors for reducing
cancer risk• Maintain a healthful weight• Adopt a physically active lifestyle• Consume a healthy diet• If you drink alcohol, limit consumption