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Nutrition Process by which food is taken into the body and changed into a form that can be utilized by cells Nutrients Food substances that the body uses for normal growth, maintenance, and repair Bulk of organic nutrients used as fuel to produce ATP (energy) Energy values of foods measured in units called kilocalories (kcal) Nutrients (cont’d) Most, but not all are ingested Some synthesized in cells Major nutrients Make up bulk of what we eat Carbohydrates, proteins, lipids Vitamins and minerals– minute amounts Water Nutrients (cont’d) Essential nutrients Cannot be synthesized by body cells Must be ingested in the diet Carbohydrates Composed of simple sugar subunits Primary source of energy Monosaccharides – can be absorbed into bloodstream Glucose Carbohydrates (cont’d) Disaccharides Polysaccharides – complex carbohydrates Starch Glycogen Cellulose (cannot be digested) = fiber Carbohydrates (cont’d) Obtained primarily from plant products Starches Vegetables, seeds, grains, and nuts Simple sugars Fruits and candy Glycogen Meat Too little = loss of weight Too much = obesity Carbohydrates (cont’d) Minimum of 100 grams/day 125-175 grams/day is recommended Concentrate on complex carbohydrates 55% of total calories 4 calories/gram Proteins Made up of amino acids Structural building blocks of body Body can only make 12 of 20 To obtain the other 8 (essential amino acids) one must eat animal sources (complete proteins) meat milk cheese eggs Proteins (cont’d) Incomplete proteins (low in one or more essential amino acids) Legumes Nuts Seeds Must be combined .8 grams/ kg of body weight 4 calories/gram Too little = weight loss & tissue wasting, anemia & edema Too much = obesity Lipids Help body absorb fat soluble vitamins Triglycerides - neutral fats Most abundant form of dietary fat Provide reserve energy, cushion body organs, insulates Phospholipids Synthesize plasma membranes and myelin Lipids (cont’d) Cholesterol Not used for stored energy Plasma membranes Structural basis of vit. D, steroid hormones, and bile salts Lipids (cont’d) Saturated fats Solid Animal products – meat, dairy Some plants - coconut Unsaturated fats Liquid Seeds, nuts, veg. oil Lipids (cont’d) Cholesterol Egg yolks, meat, milk products Linoleic and linolenic acids – essential fatty acids Body cannot synthesize Must be ingested Lipids (cont’d) Less than 30% of total intake Replace sat. fats with unsaturated 250 mg or less of cholesterol Too little = loss of wt.; rapid loss of heat Too much = obesity 9 calories/gram Vitamins Organic compound required in small amounts for growth and health Coenzymes - assist enzymes in the regulation of physiological processes Vitamins (cont’d) Most are not made in the body Must be taken in via foods or vitamin supplements Exceptions D – made in skin B and K - made by intestinal bacteria Beta carotene – converted to A Vitamins (cont’d) Water-soluble Absorbed along with water across the intestinal wall B-complex vitamins & Vit. C Exception – B12 – must bind to intrinsic factor to be absorbed Not stored in large amounts in the body Excreted in urine if not needed Damaged during food processing and cooking Vitamins (cont’d) Fat-soluble Bind to fats and are absorbed along with the fat products of digestion Vit A, D, E, and K Except for K, stored in body Can have vitamin toxicity, especially vitamin A Not easily damaged by cooking and food processing Vitamins (cont’d) Antioxidants A,C, & E Disarm tissue-damaging free radicals and have anticancer effects Minerals Inorganic molecules Make up about 4% of body by weight (most in bones and teeth) Most important Ca & P But K, S, Na, Cl, Mg also essential Mineral-rich foods: vegetables, legumes, milk, some meats Minerals (cont’d) Incorporated into structures that need reinforcement for strength Work with other nutrients to ensure a smoothly functioning body Fine balance between uptake and excretion important Retain needed amounts while preventing toxic overload Metabolism All chemical reactions necessary to maintain life Anabolism Reactions in which larger molecules or structures are built from smaller ones Energy required Catabolism Processes that break down complex structures to simpler ones Energy released and captured to make ATP Carbohydrate Metabolism As glucose is oxidized, CO2, water, and 36 ATP are formed Cellular respiration Hyperglycemia – excessively high levels of glucose in blood Some of excess stored as glycogen or converted to fat Hypoglycemia – blood glucose levels too low Liver breaks down glycogen and releases glucose to the blood Lipid Metabolism Provide reserve energy When carbohydrates are not available, more fats are oxidized to produce ATP Excessive fat breakdown causes blood to become acidic. Excess dietary fat stored in subcutaneous tissue and other fat deposits Protein Metabolism Amino acids most important anabolic nutrients Form all protein structure and the bulk of the body’s functional molecules Amino acids are actively taken up from the blood by tissue cells Once absorbed into cells, may be used to synthesize needed proteins, or serve as a secondary energy source Protein Metabolism (cont’d) Amino acids are oxidized to form ATP mainly when other fuel is not available Ammonia, released as amino acids are catabolized, is detoxified by liver cells that combine it with CO2 to form urea Role of Liver in Metabolism The body’s main metabolic organ Plays a crucial role in processing (or storing) virtually every nutrient group. Maintains homeostasis of blood glucose levels Degrades hormones Detoxifies drugs and alcohol Synthesizes plasma proteins Role of Liver in Metabolism (cont’d) Forms nonessential amino acids and converts ammonia to urea Packages fatty acids into forms that can be stored or transported Stores certain vitamins Conserves iron salvaged from worn-out RBC Makes cholesterol and secretes cholesterol’s breakdown products in bile Lipoproteins Fats and cholesterol are transported in the blood by lipoproteins High-density lipoproteins (HDLs) Transport fats from tissues throughout the body to the liver Broken down to become part of bile Energy is used to power cellular activities “Good cholesterol” Levels 35-60 okay; above 60 – thought to protect against heart disease Lipoproteins (cont’d) Low-density lipoproteins (LDLs) Transport cholesterol from liver to tissues “Bad cholesterol” High levels – 160 or above Very low-density lipoproteins (VLDLs) Converted to LDLs in liver Body Energy Balance Energy intake = total energy output (heat + work + energy storage) When balanced, weight remains stable When not, weight is either lost or gained Regulation of Food Intake Factors thought to be involved in regulating eating behavior: Rising and falling levels of nutrients Hormones Body temperature Psychological factors Metabolic Rate Three major food nutrients yield different amounts of energy: Carbohydrates and proteins: 4 kcal/g Fats: 9 kcal/g Metabolic Rate (cont’d) Basal Metabolic Rate (BMR) Total amount of energy used by the body when one is in a basal state (at rest) Energy needed to just perform essential life activities Factors influencing BMR: Surface area, age, gender, stress, hormones Thyroxine – metabolic hormone Metabolic Rate (cont’d) Total Metabolic Rate (TMR) Number of calories used by the body to accomplish all ongoing daily activities Increases greatly as muscle activity increases When TMR = total calorie intake, weight remains constant Regulation of Body Temperature Body temperature - balance between heat production and heat loss Normally 35.60C to 37.80C As food is catabolized to form ATP, more than 60% of energy released escapes as heat, warming the body Regulation of Body Temperature (cont’d) Hypothalamus initiates the following, as necessary, to maintain body temperature within normal limits: Heat-loss processes: Radiation of heat from skin and evaporation of sweat or Heat-promoting processes: Vasoconstriction of skin blood vessels and shivering Regulation of Body Temperature (cont’d) Fever (controlled hyperthermia) represents body temperature regulated at higher than normal levels Weight Loss 1. Determine you resting metabolic rate (Weight X 10) 2. Determine calories needed for activities • Bicycling 10 mph 2.7 cal/lb/hr • Dancing 2.6 cal/lb/hr • Jogging 6 mph 4.2 cal/lb/hr • Walking 3.5 mph 2.4 cal/lb/hr • Weight training 1.9 cal/lb/hr Weight Loss 3. Determine calories for normal activities. Sedentary add 20 - 40 %RMR Moderately active add 40 - 60%RMR Very active add 60 - 80%RMR 4. Add 1, 2, & 3 together 5. Subtract 20% of total calories needed Weight Gain • Same as weight loss, but add 20% • 60-70% Carbohydrate • 10-15% Proteins • Rest = Lipids