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Chapter 12

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Food Science
FOOD 2010
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Chapter 3 Human Nutrition and Food 31 Proper NutritionMaking the right food choices Too much or too little of a good thing malnutrition can result from consuming too many ro too few nutrients and caloriesProper nutrition implies an adequate and balanced consumption of foods and utilization of all the essential nutrients an individual needs Macronutrientsnutrients humans must consume in the largest amounts including carbohydrate lipid and proteinMicronutrientsnutrients the body requires in lesser amounts including the vitamins and minerals Thee general functions 1 To form body structures2 To serve as regulators of body processes on a molecular and biological level3 To provide energy by being broken apart during metabolism Malnutritionimplies an imbalance too much or too little intake of essential nutrients resulting in poor nutrition and health Undernutritiona dietary deficit for one or more nutrients occurs and deficiency diseases resultOvernutritionexcessive intake of one or more nutrient may lead to toxic response and overdose disease The dietary guidelines and the food guide pyramid59 Figure 31The food guide pyramid a visual representation of a healthy diet Bread cereal and pasta Vegetables Milk yogurt and cheeseFats oils and sweets Fruits Meat poultry fish dry beans eggs and nuts Table 31 The dietary guidelines for Americans Aim for fitness o Ain for a healthy weight Be physically active each dayBuild a healthy baseo Let the food pyramid guide your food choiceso Choose a variety of grains daily especially whole grainso Choose a variety of fruits and vegetables daily Choose sensiblyo Choose a diet that is low in saturated fat and cholesterol and moderate in total fato Choose beverages and foods that limit your intake of sugarso Choose and prepare foods with less salt If you drink alcoholic beverages do so in moderation Digestion Absorption and Transport of food Digestionsubstance called enzymes are largely responsible for the digestion or breakdown of food molecules into absorbable units or piecesFigure 32Enzyme action converting molecules into smaller units In enzyme reactions it is possible to identify substrate enzymes and produt names like lactose lactase glucose and galactose Bioavailabilitythe degree to which nutrients are digested by human enzymes in the digestive tract and absorbed by the bodyAbsorption Occurs when digested nutrients enter the bloodstream through the capillaries of the small intestine o By simple diffusion small lipids and water freely cross into the mucosal cellso By facilitated diffusion watersoluble vitamins utilize a carrier to transport them into the mucosal cellso The process of active transport causes nutrients such as a glucose and the amino acids to be absorbed into the mucosal cellswith the cost of energy inputTransport Chylomicrons travel via the lymphatic system to the heart because large molecules of fat digestion cannot travel directly into the capillaries and to the heart Nutrients to be transported through the lymphatic system are picked from the mucosal cells by small vessels called lacteals Regulating digestion and absorptionHomeostasisbodys tendency to maintain a state of chemical and metabolic equilibrium Hormoneschemical messenger secreted by a variety of glands which travel to one or more specific target organs to produce an effect such as restoring normal conditions Table 32 Summary of chemical digestion see page 62o Gastrinsecretin are examples of gastrointestinal hormones enterogatrones Cholecystokinin CCKthe name of the intestinal hormone that causes the gallbladder to release bile and also slows gastrointestinal tract motility Reading food labels Info needs to be provided o Product name and place of businesso Product net weighto Product ingredient contento Company name and addresso Product code UPC bar codeo Product dating if applicable o Religious symbols if applicableo Safe handling instructions if applicable raw meatso Special warning instructions if applicable aspartame NOTENutrient daily values are standard values for use on food labels They are the basis upon which label claims like low in sodium a good source of iron or high in calcium are made possible Any food providing ten percent or more of the Daily Value for a nutrient is a good source while 20 percent is termed high in that nutrient When consumers make Daily Value comparisons from product to product or label to label they can make better informed food selections 32 The Nutritional Role of the Macronutrients Water has 5 Major Functions Water helps regulate body temperature Water lubricates the eyes spinal cord gastrointestinal tract and joints and provide for the saliva in the mouth Water the medium for metabolic chemical reactions allowes reactants and products tocome in contact with each other and with enzymes when necessary Water participates in many reactions eg hydrolysis Water serves as a carrier and aids in the movement of nutrients during digestion absorption and circulation as well as the excretion of wastes and toxinsMetabolic water water is not only present in foods and beverages it is produced during the metabolism of nutrient molecules in body cells Electrolytesspecific mineral elements inside and outside of the body cells that conduct electrical charges NAClNaClKClKClCarbohydratesOur basic fuel All carbohydrates are composed of H O and C Simple carbohydrates Glucosemonosaccharide used as the preferred body fuel
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