Chapter 5 LIPIDS Triglycerides Phospholipids and Sterols TYPES

Chapter 5 - LIPIDS Triglycerides, Phospholipids, and Sterols

TYPES OF LIPIDS 1. Triglycerides 2. Phospholipids 3. Sterols

TRIGLYCERIDES n Triglycerides – Fats & Oils 1. Predominate form of fat in foods and major storage form of fat in the body 2. Structure – composed of 3 fatty acids + glycerol

Fatty Acids n Organic acid (chain of carbons with hydrogens attached) that has an acid group at one end & a methyl group at the other end Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fatty Acids & Triglycerides n glycerol + 3 fatty acids triglyceride + H 2 O Copyright 2005 Wadsworth Group, a division of Thomson Learning

FATTY ACIDS § Fatty Acids – carbon chains, vary in: 1. Length – affects absorption 2. Saturation –chemical structure; affects cooking & storage properties and health

n Length of carbon chain Stearic acid – 18 -carbon, saturated Simplified structure Copyright 2005 Wadsworth Group, a division of Thomson Learning

FATTY ACIDS Saturation § Saturated fatty acid – carbon chains filled with hydrogen atoms (no C=C double bonds) 1. Saturated fat – triglyceride containing 3 saturated fatty acids, such as animal fats (butter, lard) & tropical oils (palm, coconut) 2. Appear solid at room temperature

FATTY ACIDS § Unsaturated fatty acid – carbon chains lack some hydrogens (>1 C=C double bond) 1. Monounsaturated fat – triglyceride containing fatty acids with 1 double bond; i. e. canola & olive oil 2. Polyunsaturated fat- triglycerides containing a high % of fatty acids with >2 double bonds; i. e. corn, safflower, soybean, sunflower oils and fish; 3. Appear liquid at room temperature

Oleic acid – 18 -carbon, monounsaturated Linoleic acid – 18 -carbon, polyunsaturated

Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fatty Acids n Location of double bonds n Omega number – refers to the position of the double bond nearest the methyl (CH 3) end of the carbon chain n Omega-3 fatty acid n Omega-6 fatty acid Copyright 2005 Wadsworth Group, a division of Thomson Learning

Omega-3 and Omega-6 Fatty Acids Compared Copyright 2005 Wadsworth Group, a division of Thomson Learning

FATTY ACIDS § Hydrogenated – addition of hydrogen to unsaturated fat 1. Makes it more “solid” or firm 2. Effects stability and protects against oxidation; more “shelfstable” 3. Widely used by food industry in margarine, shortening, peanut butter, baked goods & snack food

Hydrogenation Copyright 2005 Wadsworth Group, a division of Thomson Learning

Hydrogenation Cis vs. trans-fatty acids n In nature, most double bonds are cis meaning that the hydrogens next to the double bonds are on the same side of the carbon chain When a fat is partially hydrogenated, some of the double bonds change from cis to trans n

Cis- and Trans-Fatty Acids Compared Copyright 2005 Wadsworth Group, a division of Thomson Learning

PHOSPHOLIPIDS n Phospholipids – similar to triglycerides in structure except only 2 fatty acids + choline Phospholipids in foods: Lecithin, egg yolks, soybeans, wheat germ, peanuts

Lecithin Copyright 2005 Wadsworth Group, a division of Thomson Learning

Phospholipids 1. Functions: part of cell membranes and acts as an emulsifier (helps keep fats in solution) 2. Not a dietary essential; made by the liver

Phospholipids Copyright 2005 Wadsworth Group, a division of Thomson Learning

Sterols Structure consists of carbon rings Copyright 2005 Wadsworth Group, a division of Thomson Learning

STEROLS § Important part of: 1. 2. 3. 4. 5. Sex hormones – testosterone Vitamin D Bile (aids fat digestion) Adrenal hormones - cortisol Cholesterol – in foods and made by the liver; dietary sources include egg yolks, liver, meats, dairy products

Fat Digestion n Hydrolysis n Triglycerides monoglycerides, fatty acids, glycerol Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fat Digestion Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fat Digestion n n Mouth n Melting n Lingual lipase Stomach n Churning and mixing n Gastric lipase Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fat Digestion n n Small intestine n Pancreatic lipases n Intestinal lipases Small intestine n CCK n Bile and emulsification

Emulsification of Fat by Bile Copyright 2005 Wadsworth Group, a division of Thomson Learning

Fat Digestion Overview Copyright 2005 Wadsworth Group, a division of Thomson Learning

Lipid Transport n Lipoproteins – clusters of lipids and proteins that are used as transport vehicles for fat n Chylomicrons n VLDL = very-low-density lipoproteins n LDL = low-density lipoproteins n HDL = high-density lipoproteins Copyright 2005 Wadsworth Group, a division of Thomson Learning

Size & Compositions of Lipoproteins

Functions of Fats n In the body, fats provide: 1. Energy – 9 kcals/gm A. Supplies 60% of body’s energy needs at rest B. Stored as adipose tissue 2. Insulation & protection 3. Cell membrane constituents

Functions of Fats n In foods, fats: 1. 2. 3. 4. Provide energy (9 kcal/gm) Contribute flavor, aroma, and tenderness Provide satiety Carry fat-soluble vitamins (A, D, E & K) 5. Provide a source of essential fatty acids

Fatty Acids § Essential fatty acids – 2 polyunsaturated fatty acids that must be provided in diet 1. Linoleic – omega-6 fatty acid and Linolenic – omega-3 fatty acid 2. Founds in plant oils, nuts, seeds, whole grains and fish 3. Play a role in normal growth & development and may prevent heart disease, hypertension, arthritis & cancer

Copyright 2005 Wadsworth Group, a division of Thomson Learning

Health Effects of Fats Excess fat intake contributes to many diseases including: 1. Obesity 2. Diabetes 3. Cancer 4. Heart disease § How? 1. High fat diets = high kcal diets 2. High saturated fat intake raises blood cholesterol 3. High fat intakes may promote cancer n

Health Effects of Lipids n Risks from trans fats n Risks from cholesterol n Risks from saturated fats Copyright 2005 Wadsworth Group, a division of Thomson Learning

Saturated Fats in the U. S. Diet

Dietary Cholesterol Copyright 2005 Wadsworth Group, a division of Thomson Learning

Health Effects of Lipids n n Benefits from monounsaturated fats and polyunsaturated fats Benefits from omega-6 and omega -3 fats 1. May reduce blood cholesterol & help prevent cancer Copyright 2005 Wadsworth Group, a division of Thomson Learning

Dietary Recommendations 1. Limit total fat intake to <30% of kcals Example: If 2000 kcal diet, then 2000 x. 30 = 600 kcals/9 kcals per gram = 65 gms of protein 2. Limit cholesterol to <300 mg/day 3. Saturated & polyunsaturated fats each <10% of kcals

Cutting Fat Cuts Calories and Saturated Fat Copyright 2005 Wadsworth Group, a division of Thomson Learning

Dietary Recommendations 1. Use all fats in moderation *1 tsp fat = 5 gm = 45 kcals 2. Beware of “hidden fats” – added to convenience foods, processed foods, & in cooking 3. Choose lean meats, skinless poultry, nonfat dairy products; limit meats to <7 oz. /day 4. Choose fish 2 -3 times/week 5. Choose monounsaturated fats – canola, olive, peanut, or sesame oils; avoid hydrogenated oils 6. Limit egg yolks to 3 -4/week

Heart-Healthy Choices Copyright 2005 Wadsworth Group, a division of Thomson Learning

Copyright 2005 Wadsworth Group, a division of Thomson Learning

Copyright 2005 Wadsworth Group, a division of Thomson Learning

Comparing Butter & Margarine Labels

Fat Substitutes § Types: 1. Carbohydrate based – i. e. Oatrim & Z-Trim; made from plant fibers 2. Protein based – i. e. Simplesse; made from egg white or milk protein 3. Fat based – i. e. Olestra; made from sucrose & fatty acids; passes through body undigested

Fat Substitutes n B. Do they work? 1. Potential health benefits – promote weight loss and lower blood lipids 2. But like sugar substitutes, many people just eat more instead of replacing fat 3. Side effects possible with Olestra 4. Use in moderation