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Nutrition Energy Metabolism and Carbohydrates Low calorie sweeteners Sugar alcohols Natural sweeteners derived from monosaccharides 1.6 to 2.6 calories/ gram Sorbitol Mannitol Xylitol Objectives Define terms in the vocabulary Describe how energy is released from carbohydrates Estimate the daily energy requirements for young, healthy adults at moderate activity. State 3 factors that increase caloric requirements Define Glycemic Response Name sources of carbohydrates in the diet. State uses of carbohydrates in the body List 4 problems resulting from excess CHO intake Define fiber and describe its use in the diet. Objectives: Energy Metabolism Discuss 3 different ways the body can use food for energy. Describe how the body handles excess intake of energy producing foods. Define the difference between anabolism and catabolism Estimate the BMR Discuss the importance of regular exercise. Vocabulary Carbohydrates Fiber Insoluble fiber Functional fiber Absorption Metabolism Glycemic Index Energy metabolism Anabolism Catabolism Basal Metabolism Aerobic Exercise Carbohydrates a class of energy-yielding nutrients that contain only carbon, hydrogen, and oxygen, hence the common abbreviation of CHO major function of carbohydrates is to provide energy, which includes sparing protein and preventing ketosis Functions Provide energy for cells Supplies 4 cal/Gm Spare protein Prevention of ketosis Carbohydrates Classifications – – Simple Complex Classification is based on the number of single sugar molecules they contain Carbohydrates: Sugars Monosaccharide: single (mono) molecules of sugar (saccharide) Disaccharide: “double sugar” composed of 2 (di) monosaccharides Polysaccharide: carbohydrates consisting of many (poly) sugar molecules Monosaccharides – – – – Fructose, galactose and glucose Each contains one sugar molecule Monosaccharides Do not require digestion before absorption Glucose Glucose can be – – – – converted to glycogen used to make nonessential amino acids used for specific body compounds converted to fat and stored in adipose tissue Disaccharides Two linked monosaccharides Sucrose= glucose + fructose Maltose= glucose + glucose Lactose= glucose + galactose Sugars: Not always a “sweet thing” Sugars--as well as starches--promote dental decay by feeding bacteria in the mouth that produce an acid that damages tooth enamel Sugar is also a source of empty calories The higher the intake of empty calories, the greater the risk of an inadequate nutrient intake, an excessive calorie intake, or both A diet high in sugar is at risk for iron deficiency Americans’ intake of sugar and artificial sweeteners is rising Sugar: Too much of a good thing Dental caries Behavioral problems in children Obesity Diabetes mellitus Heart disease Most common sources of added sugar in the American diet Soft drinks Cakes, cookies, pies Fruit drinks and punches Dairy desserts such as ice cream Candy A word about HFCS Princeton study High fructose corn syrup is commonly used in place of sugar in processed foods in the USA. The average American eats 41.5 lbs of high fructose corn syrup per year Soft drink consumption has doubled for females and tripled for males since the late 1970’s Relative sweetness of sugars Carbohydrates: Found in every level of the food Pyramid starches are most abundant in the Bread, Cereal, Rice, and Pasta group, the Vegetable group, and the plant foods found in the Meat and Poultry group natural sugars occur in the Fruit group and in the Milk, Yogurt, and Cheese group the apex contains sugars and other sweets such as candy, gelatin, and soft drinks RDA for Carbohydrates The RDA for carbohydrates is set as the minimum amount needed to fuel the brain but not an amount adequate to satisfy typical energy needs Most experts recommend that 45% to 65% of total calories come from carbohydrates Added sugars limited to 6-10% of calories 25 - 38 g of fiber are recommended daily for adult women and men respectively Complex Carbohydrates Composed of long chains of glucose molecules – – Starch: storage form of glucose in plants Glycogen: storage form of glucose in animals and humans A group name for starch, glycogen, and fiber – Dietary fiber: carbohydrates and lignin--natural and intact components of plants that human enzymes cannot digest Fiber Total fiber: total fiber = dietary fiber + added fiber Insoluble fiber: nondigestible carbohydrates that do not dissolve in water Soluble fiber: nondigestable carbohydrates that dissolve to a gummy, viscous texture Fiber---It’s not just wool and cotton Insoluble – – – Give texture to plant foods Increase stool weight to “keep you regular” Found in bran, skins, seed coverings, whole grains, dried legumes, vegetables Soluble – – – Lower serum cholesterol Improve glycemic control in diabetics Found in apples, dried legumes, vegetables, oats, rice hulls Fiber Functional fiber: as proposed by the Food and Nutrition Board, functional fiber consists of extracted or isolated nondigestible carbohydrates that have beneficial physiological effects in humans Fiber The most popular American foods do not represent rich sources of fiber Whole grains, bran cereals, dried peas and beans, and unpeeled fruits and vegetables are the best sources of fiber Grains Refined grains and refined flours: – consist of only the endosperm (middle part) of the grain and, therefore, do not contain the bran and germ portions Whole grains and whole grain flours: – contain the entire grain, or seed, which includes the endosperm, bran, and germ What is in a whole grain? Endosperm – Bran – Energy Fiber, vitamins Germ – Vitamins, minerals Health Benefits of Fiber Promotes bowel regularity Hastens bowel transit time Prevention of diverticular disease Lowers cholesterol, triglycerides to improve heart health Help prevent certain cancers Weight control How to increase dietary fiber Choose a ready-to-eat cereal with 5 grams of fiber or more per serving Eat dried peas and beans two to three times/week Replace refined grains with whole grains Eat at least five servings of fruits and vegetables daily Eat a variety of plant foods daily Increase fiber intake gradually to avoid GI intolerance Consume adequate fluid Carbohydrate Digestion Majority of carbohydrate digestion occurs in the small intestine, where disaccharides and starches are digested to monosaccharides Monosaccharides are absorbed through intestinal mucosal cells and transported to the liver through the portal vein In the liver, fructose and galactose are converted to glucose The liver releases glucose into the bloodstream Fiber is fermented by bacteria in the colon to produce water, gas, short-chain fatty acids and other compounds. Enzymes Amylase Maltase Sucrase Lactase Absorption Glucose, fructose and galactose are abosorbed through intestinal mucosa Travel to liver via portal vein Soluble fiber slows the absorption of glucose Unabsorbed starch and fiber excreted in stool Metabolism Fructose and galactose converted to glucose Liver releases glucose into blood Hormones maintain constant BG Insulin Glycogen Glucocagon Non-essential amino acids Fat Carbohydrates and serum glucose Glycemic response: – – the effect a food has on the blood glucose concentration how quickly the glucose level rises, how high it goes, and how long it takes to return to normal Glycemic index: – – a numeric measure of the glycemic response of 50 g of a food sample the higher the number, the higher the glycemic response Glycemic index and exercise endurance The types of carbohydrate eaten before, during, and after prolonged exercise influences an athlete’s endurance – – – low glycemic index carbohydrates – eat before prolonged exercise moderate to high glycemic index carbohydrate foods – eat during long distance events to ensure adequate glucose availability high glycemic index foods – eat after exercise to enhance glycogen repletion compared to low glycemic index carbohydrates Artificial Sweetners Artificial sweeteners: synthetically made sweeteners that do not provide calories Acceptable Daily Intake (ADI): – – estimated amount of artificial sweetener per kilogram of body weight that can be safely consumed every day over lifetime without risk usually reflects an amount 100 times less than the maximum level at which no observed adverse effects have occurred in animal studies Artificially sweet Be choosy about carbohydrate calories Eat a diet based on whole grain breads and cereals with plenty of fruits, vegetables, and dried peas and beans---not an ad lib intake of products made with white flour and white sugar High carbohydrate should be achieved with wholesome, unprocessed foods for optimum health benefits and weight management Lower your sugar consumption It's been suggested that the supposed link between high fructose corn syrup and obesity is not due to the high fructose corn syrup itself, but to the increasing consumption of sweeteners in general, especially soft drinks. The USDA recommends that a person with a 2000 calorie, balanced diet should consume no more than 32 g (8 tsp) of added sugar per day. Here are some sweet foods and the percentage of the daily recommended amount of sweeteners they provide: typical cup of fruit yogurt - 70% cup of regular ice cream - 60% 12-ounce Pepsi - 103% Hostess Lemon Fruit Pie - 115% serving of Kellogg's Marshmallow Blasted Froot Loops - 40% quarter-cup of pancake syrup - 103% Cinnabon - 123% large McDonald's Shake - 120% large Mr. Misty Slush at Dairy Queen - 280% Burger King's Cini-minis with icing - 95% Energy relatively abstract in that it cannot be defined by its size, shape, or mass neither created nor destroyed but changes from one form to another without being used up extracted from nutrients stored within cells as a source of immediate fuel larger amounts of energy are available in glycogen and fat tissue to fuel activity of longer duration synonymous with calories Energy Metabolism a dynamic process that constantly changes with the influx of nutrients, the availability of stored energy, and the demands of fueling activity how energy from carbohydrates, proteins, and fats is extracted and used. encompasses the processes of anabolism and catabolism that occur continuously as the body uses energy to synthesize compounds or extracts energy from the breakdown of nutrients from food or body storage Anabolism an energy-us ing proc es s that oc c urs c onti nuous ly in al l people as c ell s or subs tanc es are replac ed after normal wear and tear reas s embles nutrients i nto c ompounds for s torage Regardl es s of the s ourc e, cal ories eaten i n exc ess of need are c onverted to fatty ac i ds and s tored as body fat Catabolism breakdown of large molecules into smaller ones glycogen is broken down into glucose protein into amino acids triglycerides into glycerol and fatty acids These four basic units catabolize into smaller substances and ultimately into energy This energy is trapped in adenosine triphosphate (ATP) and stored in every cell until needed Whether from food or body storage, glucose, amino acids, glycerol, and fatty acids all eventually enter the tricarboxylic acid cycle (Krebs’ cycle) and electron transport chain to yield energy as needed Nutrient availability Nutrients broken down into pyruvate, namely glucose, glycerol, and glucogenic amino acids, can be synthesized into glucose as needed by the body Nutrients broken down into acetyl CoA, namely fatty acids and ketogenic amino acids, cannot be resynthesized into glucose and so cannot fuel glucose-requiring cells of the brain, nervous tissue, and red blood cells when glucose from food or glycogen is unavailable Glucose availability B reaki ng down body prot ein to yield glucose i s expensi ve because onl y about half of ami no acids can actually be converted to gl ucose Y et it i s more ef fici ent compared to the small amount of glucose available from glycerol in stored tri glycerides (5% of the triglyceri de molecule is glycerol) Fasting During prolonged fasting, the brain and nervous However, Another body protein catabolism continues adaptive mechanism is that metabolism Aerobic metabolism vs. Glycolysis Cells’ immediate source of fuel is stored in ATP, which is supplemented with a small supply of creatine phosphate Neither requires oxygen to be burned Glucose is the only fuel that can be burned without oxygen through the process of glycolysis Glycolysis extracts only a small amount of the total available energy from glucose Aerobic metabolism includes the TCA cycle and the electron transport chain It yields the maximum amount of available energy Activity Body uses a mixture of fuels at rest and at work As duration of activity increases, amount of fat burned increases in an attempt to conserve body’s supply of glycogen As intensity of activity increases, amount of glucose burned increases because glucose is the only fuel that can be metabolized anaerobically This anaerobic metabolism manifests in breathlessness that occurs with vigorous exercise Basal Metabolism Amount of calories required to fuel involuntary activities of the body at rest after a 12-hour fast In essence, it is the caloric cost of staying alive Calculating BMR 1) Multiply healthy weight (in pounds) by 10 for women and 11 for men; or 2) Harris-Benedict equation: – – Males: 66 + (13.7 x W) + (5 x H) – (6.8 x A) Females: 655 + (9.6 x W) + (1.7 x H) – (4.7 x A) Where W = actual weight in kg H = height in cm A = age in years BMR is influenced by numerous factors Body composition--lean vs. fat tissue Growth Hormones Fever Height Environmental temperature Starvation, fasting, and malnutrition Weight loss from dieting Stress Certain drugs Total daily calorie expenditure equals the amount of calories spent on voluntary activities (physical activity) and on involuntary activities (basal metabolism) For most Americans, basal metabolism represents 60% to 70% of total calories burned Thermic effect of food is the cost of digesting, absorbing, and metabolizing food At about 10% of total calories consumed, it is a small part of total energy requirements Estimating Total Calorie Expenditure Choose the category that fits activity level Multiply BMR by: – – – – 1.2 for sedentary 1.3 for light activity 1.4 for moderate activity 1.5 for high activity Physical activity The vast majority of Americans do not get the recommended amount of physical activity Benefits of physical activity are dosedependent and range from significant health benefits to weight management to optimal physical fitness Exercise In the short term, exercise leads to modest weight loss if calories are not also restricted In the long term, exercise promotes weight loss by promoting fat loss and preventing loss of muscle, which contributes to metabolic rate Maximal heart rate is approximately 220 minus the individual’s age Target heart rate is obtained by multiplying maximum heart rate by the desired percent. For optimum physical fitness: Engage in moderate to high intensity aerobic exercise at 60 to 90% maximal heart rate three to five times/week, with each session lasting 20 to 60 minutes plus additional time for warm-up and cooldown Perform strength training exercises 2 to 3 times per week with each session lasting at least 15 minutes Do stretching exercises at least 3 to 4 times/week, preferably every day, to increase range of motion and flexibility How to burn 150 calories (based on a 150-pound person): Pedal a stationary bicycle for 20 minutes Practice fast dance steps for 24 minutes Work in the garden for 27 minutes Walk briskly (3.5 mph) for 33 minutes Clean the house for 38 minutes Suggestions for increasing activity: Find something enjoyable Use the buddy system Spread activity over the entire day if desired Start slowly and gradually increase activity Move more Keep an activity log Activity, exercise and weight Use activity and exercise to manage weight Exercise is vital to maintain weight loss Aim to increase energy expenditure by 10002000 calories per week Don’t expect pounds to melt away Remember that what is important is burning calories, not the actual type of fuel used