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  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: kcals as CHO ( grams) with < 200 kcals as “added sugar” (50 grams) One 12 oz. soft drink has gms sugar 0ne 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