Chapter 4 Lecture Notes
Chapter 4 Lecture Notes HS 331
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This 4 page Class Notes was uploaded by Sydney Brummett on Saturday September 24, 2016. The Class Notes belongs to HS 331 at Wichita State University taught by Dr. Lisa Wray in Fall 2016. Since its upload, it has received 16 views. For similar materials see Principles of Diet and Nutrition in Health Sciences at Wichita State University.
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Date Created: 09/24/16
Chapter 4 Lecture: Carbohydrates Carbohydrates o One of the three macronutrients o An important energy source, especially for nerve cells o Composed of atoms carbon, hydrogen, and oxygen o Good sources include fruits, vegetables, grains Glucose o The most abundant carbohydrate o Produced by plants through photosynthesis o The preferred source of energy for the brain o An important source of energy for all cells Simple carbohydrates contain one or two molecules o Monosaccharaides contain only one molecule Glucose, fructose, galactose, ribose o Disaccharides contain two molecules Lactose, maltose, sucrose Starch o Plants store glucose as polysaccharides in the form of starch o Our cells cannot use complex starch molecules exactly as they occur in plants o We digest (break down) starch into glucose o Grains, legumes, and tubers are good sources of dietary starch Glycogen o Animals store glucose as glycogen (humans too) o Stored in our bodies in the liver and muscles o Not found in food and therefore not a dietary source of carbohydrate Fiber o Dietary fiber: the nondigestible parts of plants o Functional fiber: nondigestible form of carbs with known health benefits, which is extracted from plants and added to foods Cellulose, guar gum, pectin, psyllium o Total fiber = dietary + functional fiber Dietary fiber is also classified by solubility Soluble fiber o Dissolves in water o Viscous and fermentable o Easily digested by bacteria in the colon o Found in citrus fruits, berries, oats and beans o Reduces risk for cardiovascular disease and type 2 diabetes by lowering blood cholesterol and glucose levels Insoluble fibers o Generally do not dissolve in water o Found in whole grains (e.g., wheat, rye, brown rice) and many vegetables o Promote regular bowel movements, alleviate, constipation, and reduce risk for diverticulosis Energy o Fuel daily activity o Fuel exercise o Help preserve protein for other uses When diet does not provide enough carbs, the process of gluconeogenesis converts proteins in blood and tissue into glucose o Each gram of carbs = 4 kcal o Red blood cells rely only on glucose for their energy supply o Both carbohydrates and fats supply energy for daily activities o Glucose is especially important for energy during exercise o Sufficient energy intake from carbs prevent production of ketones as an alternative energy source o Excessive ketones can result in high blood acidity and ketoacidosis o High blood acidity damages body tissues Fiber o May reduce the risk of colon cancer o Promotes bowl health by helping to prevent hemorrhoids and constipation o May reduce the risk of heart disease o May enhance weight loss o May lower the risk for type 2 diabetes o Reduces risk for diverticulosis Digestion of Carbs o Most chemical digestion of carbs occurs in the small intestine o Pancreatic amylase Enzyme produced in the pancreas and secreted into the small intestine Enzymatically digests starch to maltose o Additional enzymes secreted by cells that line the small intestine (mucosal cells) digest disaccharides to monosaccharaides o These enzymes include maltase, sucrose, and lactase o Monosaccharaides are absorbed into the cells lining the small intestine and then enter the bloodstream o Most monosaccharide are converted to glucose by the liver Glucose is released into the bloodstream to provide immediate energy Excess glucose is converted to glycogen and stored in the liver and muscles Regulation of Blood Glucose o Insulin A hormone secreted by the pancreas Transported in our blood throughout the body Helps transport glucose from the blood into cells Stimulates the liver and muscles to take up glucose and convert it to glycogen o Glucagon Another hormone secreted by the pancreas Stimulates the breakdown of glycogen to glucose to make glucose available to cells of the body Stimulates gluconeogenesis – the production of “new” glucose from amino acids o Glycemic index: a measure of a food’s ability to raise blood glucose levels Foods with a low glycemic index cause low to moderate fluctuations in blood glucose o Glycemic load: amount of carbohydrate in a food multiplied by its glycemic index o Foods and meals with a lower glycemic load: Are better for people with diabetes Are generally higher in fiber May reduce the risk for heart disease and colon cancer Are associated with a reduced risk for prostate cancer How Much Carbs Should We Eat? o The Recommended dietary Allowance (RDA) for carbohydrate is 130 g per day just to supply the brain with glucose 4565% of daily calorie intake should be in the form of carbohydrates Focus on foods high in fiber and low in added sugars o Most Americans eat too much added sugar Sugars are added to foods during processing or preparation Most common source in soft drinks Typical sources are cookies, candy, fruit drinks Unexpected sources include peanut butter, flavored rice mixes, salad dressing Added sugars are not chemically different from naturally occurring sugars, but have fewer vitamins o Sugars are blamed for many health problems Can cause dental problems and tooth decay No proven asocial with childhood hyperactivity; longterm effects not known Association with increased “bad cholesterol” and decreased “good cholesterol” Association with a higher risk for diabetes Associated with obesity o Most Americans eat too little fiberrich carbohydrates o The Adequate Intake (AI) of fiber is 14 grams per 1,000 kcal in the diet daily (or 25 g for women; 38 g for men) o Whole grain foods (grains, veggies, fruits, nuts, legume) are much more healthful sources than food with added sugar or fiber Whole grains are kernels that retain the bran, endosperm, and germ Alternative Sweeteners o Nutritive sweeteners Contain 4 kcal energy per gram Sucrose, fructose, honey, brown sugar o Sugar alcohols Contain 23 kcal energy per gram Have the benefit of a decreased glycemic response and decreased risk of dental caries o Nonnutritive (alternative) sweeteners Provide little or no energy Developed to sweeten foods without the usual risk o No Acceptable Daily Intake (ADI) has been set for saccharin (e.g., “sweet’N Low”), but it has been removed from the list of cancercausing agents o ADIs have been established for Acesulfamek (Sweet one”) Aspartame (e.g., “equal”) Sucralose (e.g. “Splenda) Diabetes o Diabetes Inability to regulate blood glucose levels Hyperglycemia – in which glucose levels are higher than normal becomes chronic Three types Type 1 diabetes Type 2 diabetes Gestational diabetes Uncontrolled diabetes can cause infections, nerve damage, kidney damage, blindness, seizures, stroke, and cardiovascular disease, and can be fatal o