Lec 3a- BPK 110 Human Nutr.:Current Iss.

Transcription

1 Lec 3a- BPK 110 Human Nutr.:Current Iss. 1. Overview Carbohydrates (CHO) 2. Types of Carbohydrates 3. Why to Include Carbohydrates in Your Diet? 4. Digestion, Absorption and Transport of Carbohydrates 1

2 Lec 3a-Learning Objectives To describe and differentiate between the different types and carbohydrates To describe the various functions of carbohydrates in the body. To understand and describe why and which carbohydrates are best to include in the diet To understand and describe the health benefits of fiber To describe the digestion and absorption of carbohydrates Copyright 2018 by Nelson Education Ltd. 2

3 1. Overview Carbohydrates (CHO) Recall from Lecture #1.. ENERGY FROM THE SUN Mooo ENERGY PLANTS HERBIVORES Grrrr CARNIVORES OMNIVORES 3

4 1. Overview Carbohydrates (CHO) Cont H 2 O + CO 2 + ENERGY FROM THE SUN PLANTS Plants make carbohydrates via photosynthesisneeds chlorophyll, sun, water (H 2 O) carbon dioxide (CO 2 ) H 2 O is absorbed in roots, CO 2 absorbed by leaves, so glucose 4

5 1. Overview Carbohydrates (CHO) Cont glucose is a molecule with 6 carbon atoms it is energy that is stored for all work of plants in their roots, flowers, stems and fruits PLANTS Plants don t use all their CHO it is a food source for: Mooo Grrrr 5

6 2. Types of Carbohydrates There are 3 types of carbohydrates of interest: Monosaccharides Disaccharides Polysaccharides 6

7 2. Types of Carbohydrates cont Sugars (Fig 4-2 S,W&P ) -6 sugar molecules of interest, note all end in -ose 3 Monosaccharides - glucose, fructose, galactose -glucose & fructose are most common -fructose is sugar found in fruits - galactose is bound to glucose in lactose in milk 3 Disaccharides - lactose, maltose, sucrose -these are pairs of bound simple sugars Lactose = glucose + galactose; sugar in milk Maltose = glucose + glucose; found in starch Sucrose = fructose + glucose; table sugar; from refined juice of sugar beets or sugarcane 7

8 2. Types of Carbohydrates Continued The Major Sugars 8

9 Starch Glycogen Cellulose (Fiber) indigestible 9

10 2. Types of Carbohydrates cont Polysaccharides-Starch, Glycogen, Fiber Starch -long strands of glucose units -a storage form of glucose by plants -starch found in seeds as energy source for next generation -starch is insoluble in water - starch usually is digestible by humans; is a glucose source Good Food Sources of Starch: grains, potatoes, beans find some others on your own. 10

11 2. Types of Carbohydrates Cont Polysaccharides - Starch, Glycogen, Fiber (Fig 4.3 S,W&P) Glycogen -a storage form of glucose by animals & humans -also long strands of glucose units but strands are longer& more branched than starch -not found in meats since their glycogen is broken down during the animal s slaughter 11

12 2. Types of Carbohydrates Cont Polysaccharides - Starch, Glycogen, Fiber Fiber -fiber in plants is the supporting structure -most fibers are polysaccharides but are not digestible - no human enzymes to break them down -Cellulose, hemicellulose & pectin are best e.g s of fiber -divided into soluble & insoluble fiber types (Table 4-2 S,W&P ) DRI Recommendations for Fibre l Men, age 19 50, 38 g/day l Men, age 51 and up, 30 g/day l Women, age 19 50, 25 g/day l Women, age 51 and up, 21 g/day 12

13 Insoluble vs Soluble Fiber-One Fiber Classification Scheme Table 4-2 S,W&P Both fiber types # moisture in stool. 13

14 3a. Why to Include Carbohydrates in Your Diet? -eat complex carbohydrate w/ starch & fiber, $simple sugars Dietary Fiber + Starch provides calories + health benefits: Mechanism (Mxn) of Health Benefits: 1. Slows absorption of nutrients, molecules & cholesterol by entrapping them 2. Stimulates bacterial fermentation-yields fatlike products that helps decrease LDL-cholesterol 3. # stool weight by holding in H Binds bile for excretion (Fig 4-5 S,W&P ) 14

15 Figure 4-4: Fibre Composition of Common Foods INSERT Figure 4-4 new content for this edition Copyright 2018 by Nelson Education Ltd. 15

16 Figure 4-5 How Fibre in Food May Lower Blood Cholesterol 16

17 3b) Health Benefits of Fiber 1) $ risk CVD (stroke, heart disease, atherosclerosis) 2) $ fiber & # sugar diets may have higher risk of diabetes 3) Helps maintain body weight; gives feeling of fullness b/c they absorb water; promotes $ caloric intake 4) Keeps GI healthy-insoluble fibers give muscles in GI a work out, helps prevent diverticulosis (Fig 4-6 S,W&P ), constipation, hemorrhoids 5) Possibly $ cancer of the colon Roughage- are fibers that aid in digestion and elimination Hands On Project: Consumer Corner pp for fiber & bread 17

18 4. Digestion, Absorption &Transport of Carbohydrates Starch starts with enzyme amylase in mouth saliva No enzyme-mediated digestion in stomach-too acidic Small intestine (SI) pancreatic amylase breaks down starch to disaccharides & smaller polysaccharides Types of starch vary in rate of digestion from none to quick i) White flour-quick; Cooked beans-slow ii) Cornstarch seed hulls are indigestible (i.e. zero digestion) 18

19 4. Digestion, Absorption &Transport of Carbohydrates Fiber digestion in GI tract Fiber many types not changed by human digestive enzymes digested by bacteria in gastrointestinal (GI) tract bacteria break down fibers & resistant starch to small fat droplets absorbed by body...helps lower LDLcholesterol bacteria by-product is gas slowly add fiber to diet 19

20 4. Digestion, Absorption & Transport of Carbohydrates Sugars Sucrose & lactose, maltose (disaccharides) from polysaccharides hydrolyzed in SI by 3 enzymes to monosaccharides: maltase hydrolyzes* maltose to 2 Glucose sucrase hydrolyzes sucrose to 1 fructose + 1 glucose lactase hydrolyzes lactose to 1 galactose + 1 glucose Glucose, fructose, galactose carried to the liver that converts fructose & galactose to glucose * hydrolyzes = cleaves/splits using water 20

21 Six Step Summary of the Digestion, Absorption and Transport of Carbohydrates (CHO): Small Intestine (SI) 1) Fiber, starch, monsaccharides move to stomach to SI; some starch is broken down by salivary amylase before reaching the SI 2) Pancreatic amylase from pancreas digests most of starch to disaccharides 3) Enzymes lactase, sucrase, maltase on surface of SI split di-saccharides to monosaccharides 4) Monosaccharides enter capillaries, dissolve in the blood & are delivered to the liver by the portal vein 5) Liver converts galactose & fructose to glucose 6) Glucose is transported dissolved in the blood 7) Fiber & resistant starch 21 travel unchanged to the colon

22 Summary for Lecture 3a 1. Overview Carbohydrates (CHO) 2. Types of Carbohydrates 3. Why to Include Carbohydrates in Your Diet? 4. Digestion, Absorption and Transport of Carbohydrates 22