Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33The The Carbohydrates: Carbohydrates: Sugars, Starches, Sugars, Starches, and Fibersand FibersChapter 4 (Lecture #2)Chapter 4 (Lecture #2)Dr. Alisha RovnerDr. Alisha RovnerUniversity of DelawareUniversity of DelawareNutrition Concepts (NTDT200)Nutrition Concepts (NTDT200)Fall 2013Fall 2013Class OverviewClass Overview•Digestion and Absorption of Carbohydrates•Glucose in the Body•Sugars•Alternative SweetenersClass ObjectivesClass Objectives•Summarize carbohydrate digestion and absorption. •Explain how the body maintains its blood glucose concentration •Describe how added sugars can contribute to health problems.No. Calories cause weight gain. Excess calories from carbohydrates are not any more fattening than calories from other sources. Despite the claims of low-carb diets, a high-carbohydrate diet does not promote fat storage by enhancing insulin resistance. In fact, a recent study published in the JADA found that consuming a low-carbohydrate diet was associated with an increased likelihood of being overweight or obese. The lowest risk was found in those who consumed about half of their calories from carbohydratesDo Carbohydrates Cause Weight Gain?Carbohydrate DigestionCarbohydrate Digestion•Ultimate goal is to to break down sugars and starches into small molecules the body can use•Large starch molecules require extensive breakdown•Disaccharides need to be broken down once•Monosaccharides don’t need to be broken downCarbohydrate DigestionCarbohydrate Digestion•Carbohydrate digestion begins in the mouth•Salivary enzyme amylase hydrolyzes starch to shorter polysaccharides and to the disaccharide maltose •Food is in the mouth for a short time so very little carbohydrate digestion takes place thereCarbohydrate DigestionCarbohydrate DigestionStomach•Swallowed bolus mixes with stomach’s acid and protein digesting enzymes•Acid continues to break down starch but doesn’t contain enzymes to digest carbohydrates•Fibers linger and delay gastric emptying which provides a feeling of fullness and satietyCarbohydrate DigestionCarbohydrate DigestionCarbohydrate DigestionCarbohydrate DigestionLarge intestines•Within 1-4 hours after a meal, all sugars and most of the starches have been digested.•Only fiber remains in the digestive tract.•Fibers attract water, which softens stools.What type of fiber helps alleviate constipation?A.Soluble B.InsolubleCarbohydrate AbsorptionCarbohydrate Absorption•Nutrient absorption takes place in the small intestines•Glucose and galactose enter the cells lining the small intestines by active transport•Fructose is absorbed by facilitated diffusion•In the liver, galactose and fructose are converted to glucoseAbsorption of Absorption of MonosaccharidesMonosaccharidesLactose IntoleranceLactose Intolerance•Normally, intestinal cells produce enough lactase (enzyme that breaks down lactose) for digestion and absorption•Lactase activity•Highest immediately after birth & with age•About 30% of people retain enough lactase to digest and absorb lactose throughout adulthoodLactose intolerance Lactose intolerance •Condition that results from inability to digest the milk sugar lactose•Symptoms include bloating, abdominal discomfort and diarrhea•May develop(caused) when intestinal villi are damaged by diseases, medications, prolonged diarrhea and malnutritionPrevalence of Lactose Prevalence of Lactose IntoleranceIntolerance•Prevalence varies among ethnic groups•80% Southeast Asians•80% Native Americans•75% African Americans•50% Hispanics•20% Caucasians•10% Northern EuropeansLactose IntoleranceLactose Intolerance•Dietary changes•Manage lactose consumption rather than restriction, total elimination usually not necessary•Most people can consume 6 grams of lactose (1/2 cup milk) without symptoms •Milk products that have been treated with an enzyme that breaks down lactose (ie. Lactaid)—lactose-free products•Non-dairy foods can contain lactose tooLactose Free DietLactose Free Diet•Complete lactose free diet can be difficult because lactose is found not only in milk/milk products but many nondairy foods.•Those on strict lactose free diet need to avoid foods that include milk, milk solids, whey (milk liquid) and casein (milk protein).•Need to check medications too since some contain lactose as a filler.Lactose in Selected FoodsCarbohydrate MetabolismCarbohydrate Metabolism•Main goal- supply cells with glucose for energy•Storing glucose as glycogen•Liver- stores about 1/3 of supply and releases glucose into bloodstream as needed•Muscle- also stores glucose but keeps most of it for themselves•Brain- maintains small amount but only provides an emergency energy reserveCarbohydrate MetabolismCarbohydrate Metabolism•Glucose for energy•Fuels most of the body’s cells•Liver stores only last for hours so need to eat carbohydrates frequently•Making glucose from protein (gluconeogenesis) •Amino acids of proteins can be converted to glucose; however, this isn’t preferable •When person doesn’t eat carbohydrates the bodies proteins are broken down to make glucoseCarbohydrate MetabolismCarbohydrate Metabolism•Fat can’t be converted to glucose to any significant extent•When person doesn’t consume enough carbohydrates ketone bodies provide an alternate fuel source•Dangerous because this disturbs acid-base balanceCarbohydrate NeedsCarbohydrate Needs•To spare body protein and prevent ketosis, the body needs at least 50-100 grams of carbohydrates a day.•Dietary recommendations are that people select abundantly from carbohydrate rich foods to provide for considerably more.The Constancy of Blood The Constancy of Blood GlucoseGlucose•Body must maintain blood glucose within a certain range•Blood glucose homeostasis regulated by 2 hormones1. Insulin （（（（（ - Moves glucose from blood into cells2. Glucagon （（（（（（（ - Brings glucose out from storage when necessaryMaintaining Blood Glucose Maintaining Blood Glucose HomeostasisHomeostasisThe Constancy of Blood The Constancy of Blood GlucoseGlucose•Balancing within the normal range (70 -100 mg/dL)•Diabetes•Insulin is either inadequate or
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