Chapter 4 THE CARBOHYDRATES Sugars Starches Fibers Carbohydrates

Chapter 4 THE CARBOHYDRATES: Sugars, Starches & Fibers

Carbohydrates (CH 2 O)n • Simple carbohydrates – Monosaccharides (single sugars) – Disaccharides (double sugars) • Complex carbohydrates – Polysaccharides (many sugars) Copyright 2005 Wadsworth Group, a division of Thomson Learning

Simple Carbohydrates Monosaccharides (C 6 H 12 O 6) Glucose Fructose Galactose Copyright 2005 Wadsworth Group, a division of Thomson Learning

Monosaccharides Glucose – dextrose or blood sugar 1. Primary fuel for the body 2. Found in all disaccharides & polysaccharides

Monosaccharides Fructose – fruit sugar 1. Found in fruit, honey, syrup 2. Converts to glucose in the body

Monosaccharides Galactose – part of lactose 1. Found in milk 2. Converts to glucose in the body

Simple Carbohydrates Disaccharides Maltose Sucrose Lactose Copyright 2005 Wadsworth Group, a division of Thomson Learning

Disaccharides Sucrose – table sugar 1. Glucose + Fructose 2. Refined from sugar beets & cane

Disaccharides Lactose – milk sugar 1. Glucose + Galactose 2. Lactose intolerance – missing digestive enzyme needed to split into two monodisaccharide parts to absorb it

Disaccharides Maltose – malt sugar 1. Glucose + Glucose 2. Found in germinating seeds & used in fermentation to produce malted beverages (beer, whiskey)

Condensation

Hydrolysis

Complex Carbohydrates Polysaccharides Glycogen Starches Fibers Copyright 2005 Wadsworth Group, a division of Thomson Learning

Polysaccharides Glycogen – long chains of glucose found in animals 1. Stored in liver & muscles 2. Helps maintain blood glucose and important source of “quick energy”, esp. during exercise (lasts only about 12 hrs)

Polysaccharides Starch – long chains of glucose found in plants 1. Cereal grains (wheat, rice, corn, etc. ), legumes (beans & peas), and root vegetables (potatoes, yams)

Polysaccharides Fiber – mostly indigestible CHO; gums, mucilages, lignin 1. Component of plant cell walls 2. Classified according to solubility in water 3. Abundant in whole grains, legumes, fruits and vegetables

Fibers Insoluble – nonviscous; cellulose, lignins Soluble – viscous & fermentable; pectins, gums, mucilages

Digestion • Mouth –Salivary amylase • Stomach –Fibers and satiety • Small Intestine -Maltase, sucrase, lactase

Digestion • Pancreas –Pancreatic amylase • Large Intestine -Fermentation of viscous fibers Ø Water, gas, short-chain fatty acid production

Carbohydrate Digestion in the GI Tract

Absorption

Metabolism Glucose in the Body • Used for energy – fuels most of the body’s cells • Stored as glycogen – 1/3 in the liver and 2/3 in muscles • Made from protein – gluconeogenesis • Converted to fat – when in excess of body’s needs

Constancy of Blood Glucose • Regulating hormones – maintain glucose homeostasis 1. Insulin – moves glucose from the blood into cells 2. Glucagon – signals the liver to release glucose into the blood 3. Epinephrine – released when emergency fuel needed

Maintaining Blood Glucose Homeostasis

Constancy of Blood Glucose • Diabetes – Type 1 diabetes • Failure of insulin production – Type 2 diabetes • Obesity • Hypoglycemia – Rare in healthy people • Glycemic response – Glycemic index

Glycemic Index

Health Effects of Sugar • Sugar in excess 1. Contains no nutrients and may contribute to malnutrition 2. Causes dental caries (tooth decay) 3. Does not cause, but can contribute to: obesity, diabetes, heart disease, & behavorial problems

Accusations Against Sugars • Sugar causes obesity • Sugar causes heart disease

Accusations Against Sugars • Sugar causes misbehavior in children and criminal behavior in adults • Sugar causes cravings and addictions – serotonin

Recommended Intakes of Sugars • DRI – No more than 25% of total daily energy intake -Limit added sugars to <10% of total energy intake Copyright 2005 Wadsworth Group, a division of Thomson Learning

Health Effects • Complex carbohydrates & fiber may reduce the risk of: -Heart disease -Diabetes -GI health -Cancer -Weight Management

Health Effects How? • Diets high in complex CHO tend to be: 1. Lower in fat and calories 2. Higher in fiber, vitamins, & minerals

Soluble Fibers • Lower blood cholesterol by binding dietary cholesterol so less absorbed • Slow glucose absorption • Slow transit of food through upper GI tract • Holds moisture in stools, softening them • Lower risk of heart disease • Lower risk of diabetes

Soluble Fibers • Gums & mucilages, pectins, psyllium • Sources –Whole-grains, fruits, legumes, seeds and husks, vegetables –Extracted and used as food additives

Insoluble Fibers • Increase fecal weight - helps form soft, bulky stools which improves G. I. motility & reduces risk of constipation, hemorrhoids, diverticulosis & colon cancer • Speed fecal passage through colon • Provide bulk and feelings of fullness (satiety)

Insoluble Fibers • Cellulose, lignins, hemiculloses • Sources – Brown rice, fruits, legumes, seeds, vegetables, wheat bran, whole grains – Extracted and used as food additives

Recommended Intakes of Carbohydrates & Fibers • RDA for carbohydrate – 130 g/day – 45% - 65% total daily energy intake with emphasis on complex -Daily Value: 300 g/day • Fiber – Daily Value: 25 g/day – AI: 14 g/1000 kcal/day

Dietary Recommendations Example: If 2000 kcal diet, then: 1100 -1200 kcals as CHO (275 -300 grams) with < 200 kcals as “added sugar” (50 grams) One 12 oz. soft drink has 36 -40 gms sugar 0 ne tsp. sugar weighs 4 gms = 9 -10 tsps!

Alternative Sweeteners Two Categories 1. Sugar Alcohols – mannitol, sorbitol, xylitol 2. Artificial sweeteners – sugar substitutes (calorie-free); in moderation, useful for blood sugar & weight control

Alternative Sweeteners Sugar Alcohols 1. CHOs that provide less energy than sucrose (2 -3 kcals/gm) because not completely absorbed 2. May cause gas, abdominal discomfort, diarrhea 3. Less cariogenic than sugar

Alternative Sweeteners Artificial Sweeteners 1. Saccharin = “Sweet ‘N Low” or “Sugar Twin” 2. Aspartame = “Equal” or “Nutrasweet” must avoid if have phenylketonuria 3. Acesulfame-K = “Sunette” or “Sweet One” 4. Sucralose = “Splenda”

Alternatives to Sugar • Acceptable Daily Intake (ADI) • Artificial sweeteners and weight control • Saccharine and cancer • Aspartame and PKU

Sugar Alternatives on Food Labels

Alcoholic Beverages • Rule of thumb to figure calories per ounce for wines and distilled spirits Wine: Multiply the “percent of alcohol by volume” by two to obtain calories/ounce Example: Zinfandel is 12. 5% alcohol by volume, 12. 5 X 2 = 25 calories/ounce Distilled Spirits (hard liquor): Proof minus 15 to obtain calories per ounce Example: 80 proof whiskey – 15 = 65 calories per ounce